SHELXT - integrated space-group and crystal-structure determination

Carbazolylphenyl ethynyl anthracenes as TTA emitters with improved horizontal alignment for the applications in OLEDs and for optical detection of the nitroaromatic explosive compounds

Synthesis and properties of the carbazolylphenyl ethynyl anthracenes with tert-butyl, methoxy, and methoxyethoxy groups are reported. The compounds exhibit remarkably high thermal stability with the temperatures of the onsets of thermal degradation exceeding 407 °C. The ionization potentials of the compounds range from 5.38 to 5.65 eV. Hole mobilities of the derivatives exceed 1 × 10-4 cm2 × V-1s-1 at high electric fields. The photoluminescence quantum yields of the toluene solutions of the compounds are in the range of 86-97 %. The low-lying triplet excited states with the energy of 1.98 eV are detected experimentally and confirmed by the theoretical calculations utilizing density-functional theory for all the studied compounds. The long-lived photoluminescence with a lifetime of up to 0.19 ms is detected for the film of tert-butylcarbazole-based emitter. Triplet-triplet annihilation as an emissive mechanism of the emitters was discussed. The solid samples of dimethoxycarbazolyl-containing derivative shows photoluminescence quantum yield of 36 %. The triplet-triplet fusion is manifested by the long-lived electroluminescence of organic light emitting diode (OLED) with this compound as the emitter and the slope of 2 of the linear plot of brightness versus current density in log-log scale. The considerable quenching of emission of the dispersions of the compounds in THF/water mixtures with a volume fraction of water of 99 % is observed after the addition of picric acid. The respective Stern-Volmer constants are in the range of 6.3 × 104-1.1 × 105 M-1.

Zirconium metal-organic cages for iodine adsorption: Effect of substituted groups and pore structures

Zirconium metal-organic cages (MOCs) have emerged as potential adsorbents for radioactive iodine absorption, one of key fission products of concern in nuclear fuel cycles. Herein a series of substituted groups functionalized Zr-MOCs were employed to investigate the influence of substituted group on iodine adsorption, in which ZrT-1-(NH2)2 showed the highest improvement on both iodine vapor and solution-based absorption. Thereafter, five longer linkers functionalized with amino groups were chosen to construct five isoreticular MOCs for iodine absorption. Among them, ZrT-2-3,3'-(NH2)2 and ZrT-3-2,2''-(NH2)2 exhibited comparable iodine vapor absorption capacity compared with ZrT-1-(NH2)2. Impressively, iodine vapor adsorption capacities (2.62 g/g and 2.50 g/g) of ZrT-1-(NH2)2 and ZrT-3-2,2''-(NH2)2, represent the second highest among all the MOCs. These five isoreticular MOCs displayed higher iodine uptake capacities via solution-based process than ZrT-1-(NH2)2. The iodine/cyclohexane uptake capacities of ZrT-2-3-NH2 and ZrT-2-3,3'-(NH2)2 and ZrT-3-2,2''-(NH2)2 are the highest among all the MOCs. Raman and XPS demonstrate the strong charge transfer from the amino-substituted linkers to absorbed iodine. Synchrotron X-ray single-crystal diffraction provides the possible iodine species distribution in the cage, clarifying the host-guest interactions between the trapped iodine and MOCs. This work may motivate the rational design of MOCs with optimized structures to enhance the adsorption properties.

Copper(II) tetrapyrazole-based complex as a new peroxidase-mimetic compound

A copper(II) tetrapyrazole-based complex of the composition of [Cu(tpyr)(H2O)(ONO2)]NO3 (1), where tpyr represents a tetradentate N-donor ligand formed by the condensation of 1H-pyrazole-5-carbaldehyde in NaOH/MeOH medium, has been prepared and characterized by elemental analysis, infrared spectroscopy, ultraviolet-visible spectroscopy, mass spectrometry, electron paramagnetic resonance and single-crystal X-ray diffraction. Spectrophotometric measurements demonstrated a remarkable peroxidase activity of the complex, which utilized hydrogen peroxide for the oxidation of phenolic compounds such as guaiacol or 3,5-dichloro-2-hydroxybenzene sulfonic acid. The optimum conditions for this reaction were found at pH 8 in ammonium bicarbonate buffer, although the activity was low but still detectable at pH 5-6 in ammonium acetate. As a peroxidase mimic, the complex exhibited enzyme-like Michaelis-Menten kinetics, showing a hyperbolic dependence of the reaction rate on hydrogen peroxide concentration. The determined Km and kcat values were 651 μmol·l-1 and 6.7 × 10-4 s-1, respectively, compared to 41 μmol·l-1 and 73 s-1 for horseradish peroxidase. EPR spectroscopy of the reaction mixture revealed no change in the copper (II) oxidation state during catalysis, suggesting that the oxidation of guaiacol may occur simultaneously with the reduction of hydrogen peroxide to water at the copper centre.

Quasi-metallic bandgap tunability at low static pressures and quintuple chromism by electron transfer in a viologen-derivative iodide

The metallized bandgap tunability at low static pressures is of vital importance to alter and optimize optical and electrical properties but it is a great challenge due to the intrinsic difficulty in reducing atomic or molecular space in crystals. The development for a material whose metallized bandgap tunability at low static pressures is accompanied by electron donor-acceptor transfer is more important because it may incorporate electron transfer related properties such as chromism. Herein, the integration of photoresponsive electron-deficient viologen ligand and electron-riched iodide ion gives rise to a charge-transfer material, [CBBPY]I2 (CBBPY = 1,1'-bis(4-cyanobenzyl)-[4,4'-bipyridine]-1,1'-diium), which displays quasi-metallic bandgap tunability and coloring responses to quintuple external stimuli such as pressure, light, electricity, organic amines, and chemical reduction. With increasing pressure, the band gap of [CBBPY]I2 is significantly narrowed and quasi-metallized from 2.4 eV to 0.8 eV at 25 GPa, also demonstrated by a drastic drop in resistance by orders of magnitude. Computational simulation predict that the material can achieve band gap closure at 45 GPa. Interestingly, [CBBPY]I2 exhibits rare phtotochromic, piezochromic, electrochromic, aminechromic and chemical chromism. Experimental and theoretical investigations have jointly revealed that piezometallization tendency and piezochromism in relatively low-pressure regimes can be attributed to the ordered arrangement and the shortening of distances of electron donor-acceptors, as well as enhancement of charge transfer induced by external pressures.

Chemical modification of monensin as a source of potent antiplasmodial agents

Malaria remains a significant public health issue and one of the leading causes of child mortality worldwide. Due to the growing problem of drug resistance, new modes of fighting the disease are searched for. In this context, ionophore antibiotics, natural compounds with high potential for combating parasitic diseases, deserve special attention. The primary representative of such compounds, monensin (MON), demonstrates exceptionally high antiplasmodial activity. In this work, the C26-amino derivative of MON was used as a convenient substrate for the synthesis of its acyl analogues, such as amides and urea. All derivatives exhibited strong activity against the hepatic stage of Plasmodium berghei infection in vitro, which exceeded that shown by the reference drug primaquine. The IC50 value for MONO-phenyl urethane (8) was less than 1 nM.

Phyllanfranins A-F, anti-inflammatory ent-cleistanthane diterpenoids from Phyllanthus franchetianus

A comprehensive chemical investigation of the EtOAc extract derived from the dried branches and leaves of Phyllanthus franchetianus H. Lév had successfully resulted to the isolation of six undescribed cleistanthane diterpenoids phyllanfranins A-F (1-6), along with three known compounds phyllarheophol C (7), phyacioid C (8), and spruceanol (9). The chemical structures of these compounds were elucidated by combined means of HRESIMS, 1D and 2D NMR spectra, together with ECD calculations. The absolute configuration of phyllanfranin A (1) was established by single crystal X-ray diffraction analysis. Notably, phyllanfranin F (6) represents the first ent-cleistanthane diterpenoid with the unique 6/6/6/6 tetracyclic system occurring in nature. Additionally, all the isolates were evaluated for anti-inflammatory activities. As a result, compounds 4 and 8 showed notable inhibitory activity against NO production in LPS-stimulated macrophages RAW264.7 cells, with IC50 values of 19.03 and 18.14 μM, respectively.

Synthesis, NMR and X-ray characterization of dibenzoannulated dimeric steroid spiroketals. Evaluation of cytotoxicity and anti-inflammatory activity

Two dibenzoannulated dimeric steroid spiroketals were obtained from cholesterol and 1,4-phenylenedimethanol. The key step in synthetic protocol is a Pd-catalyzed double spiroketalization in an adduct obtained from the double Sonogashira coupling of the 5α and 5β diastereomers of 4,5-secocholestan-5-ol. A detailed NMR characterization supported by Single Crystal X-ray Diffraction studies corroborated the obtained structures. While no cytotoxic effect was observed, the obtained compounds produced a significant reduction in the production of nitric oxide in macrophages stimulated with Lipopolysaccharide (LPS), indicating a potential anti-inflammatory activity.

Novel flucytosine salt: Structure, Hirshfild surface analysis, morphology, FIMs, and computational studies

5-Flucytosine (FC) exhibits an advanced solid-state structure, which presents challenges for its pharmaceutical development. This paper presents experimental, and theoretical studies of a novel pharmaceutical salt, fluorocytosinium chloride, HFC+.Cl-. Single crystal X-ray diffraction (SCXRD) investigation indicates that HFC+.Cl- forms crystals in the monoclinic system and P21/c space group. The structure is maintained by a series of hydrogen bonding interactions, comprising N-H···Cl, N-H···O, and C-H···F. In addition, noncovalent anion···π interactions between chloride anions and HFC+ cations play a role in establishing a three-dimensional network. Hirshfeld surface analysis (HS) and two-dimensional fingerprinting were used to enumerate the intermolecular interactions within the crystal. The results demonstrate that the H···Cl/Cl···H, O···H/H···O, and F···H/H···F interactions are the most significant. Full Interaction Maps (FIMs) analysis predicts the positions of hydrogen bond acceptors and donors, confirming the supramolecular arrangement observed in HFC+.Cl-. Computational modeling studies using the Bravais-Friedel, Donnay-Harker (BFDH), and Growth Morphology (GM) methods predict the morphology of the HFC+.Cl- crystal. Both approaches estimate a comparable crystal shape characterized by six principal facets. Density functional theory (DFT) calculations were conducted utilizing the DMol3 software to investigate the electronic structure and comprehensive reactivity features of HFC+.Cl-. The low HOMO energy suggests significant stability against electrophilic attacks, while the high HOMO-LUMO band gap indicates high chemical hardness. Fukui functions were also calculated to identify atomic sites susceptible to nucleophilic and electrophilic attacks. This study offers a comprehensive insight into the structural and electronic properties of HFC+.Cl-, offering valuable information for the development of new pharmaceutical compositions.

Exploring Zn(II)-Acetyl l-carnitine complex for simultaneous management of depression, chronic pain, and neuroprotection

Acetyl-l-carnitine (ALC) is synthesized in the brain, liver, and kidneys and plays crucial roles in energy metabolism, acetylcholine production, protein synthesis, and neuronal protection, contributing to its antidepressant and neuroprotective properties. Zinc, a vital biometal, is essential for depression and neuroprotection, exhibiting antidepressive effects alone or combined with classical antidepressants. The pharmacological benefits of metal coordination complexes often result from synergistic or additive effects. In this study, we present a novel multifunctional zinc complex, Zn(ALC)Cl2(H2O), which crystallizes in the monoclinic chiral space group P21, featuring a distorted tetrahedral Zn(II) environment. This new compound demonstrates significantly higher antidepressant activity, reducing immobility in the forced swimming test by 54 % compared to commercial ALC. Additionally, it exhibits in vivo antinociceptive properties, increases latency time, and proves effective in a diabetic neuropathy model by preventing the glucose-induced decrease in intracellular GSH levels. In vitro studies indicate that the complex can cross the blood-brain barrier and offer neuroprotection against glutamate-induced excitotoxicity and oxygen-glucose deprivation, with a drug classification of 10 versus 5 for ALC. Furthermore, under astrocytosis conditions, the Zn complex neutralizes the toxic effects of TGFβ-treated astrocytes. These findings highlight Zn(ALC)Cl2(H2O) as a promising candidate for treating depression and neurodegenerative diseases.

Unusual zig-zag-shaped Ln-radical coordination networks derived from a nitronyl nitroxide with two imidazole groups: single-crystal-to-single-crystal transformations and magnetic properties

Two unusual two-dimensional coordination networks, namely, {[Gd(hfac)3]3(NIT-Ph-3,5-bIm)2}·2.25C6H14 (1) and {[Dy(hfac)3]3(NIT-Ph-3,5-bIm)2}·2.5C6H14 (2), were obtained using the multidentate nitronyl nitroxide ligand containing two additional imidazole groups, NIT-Ph-3,5-bIm (NIT-Ph-3,5-bIm = 2-[3,5-bis(1-imidazole)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate). In these Ln-radical complexes, the multidentate nitronyl nitroxide radical ligand served as a tridentate linker, binding three LnIII ions via one NO group and two imidazole units, resulting in unique zig-zag-shaped 2D networks with KIa topology. These coordination networks underwent a single-crystal-to-single-crystal transformation from a low-temperature non-centrosymmetric space group (P21) to a room-temperature centrosymmetric space group (P21/c) accompanied by the loss of helicity in chiral chains and an order-disorder transition of the LnIII ions. Direct-current magnetic susceptibility studies of the Gd derivative showed dominant ferromagnetic Gd-NO exchange. Dynamic magnetic studies of the Dy analogue displayed temperature-dependent nonzero out-of-phase signals, indicating slow magnetic relaxation behavior.

Physical properties and cytotoxicity of Cu(II) and Zn(II) complexes with a TMS-substituted indolo[2,3-c]quinoline-derived Schiff base

The incorporation of non-native chemical elements, such as silicon, into drug molecules has gained significant attention as a strategy to broaden the chemical space in medicinal chemistry and develop novel drug candidates. Traditionally, research has focused on the isosteric replacement of a carbon atom with silicon ("silicon switch") in known drug structures or the attachment of a trimethylsilyl (TMS) group to biologically active scaffolds. In this study, a TMS-substituted indoloquinoline-based Schiff base (HLTMS) and its corresponding metal complexes, Cu(HLTMS)Cl2 (1) and Zn(HLTMS)Cl2 (2), were synthesized and comprehensively characterized using elemental analysis, spectroscopic techniques (IR, UV-vis, 1H and 13C NMR for HLTMS and 2), ESI mass spectrometry and single-crystal X-ray diffraction (SC-XRD) for 1 and electron diffraction (ED) for 2. The attachment of the TMS group enhanced the lipophilicity of HLTMS, while complex formation with Cu(II) substantially improved the antiproliferative activity. Exploitation of their intrinsic fluorescence to investigate cellular uptake and intracellular localization in cancer cells was impeded by limited solubility. Both HLTMS and 2 were found to generate reactive oxygen species under cell-free conditions in accord with their redox activity established by cyclic voltammetry. The photochemical activity of the indolo[2,3-c]quinoline-based proligand HLTMS and its complexes 1 and 2 has been disclosed. The compounds exhibited significant toxicity on various human cancer cells and disrupted the mitochondrial membrane potential, suggesting the contribution of mitochondrial dysfunction, triggered by HLTMS and its metal complexes, to their toxic effects. These findings highlight the potential of TMS-substituted Schiff bases as promising anticancer drug candidates.

Fine-Tuning the Excited-State Dynamics of Heteroleptic Ruthenium(II) Polypyridyl Complexes with Systematic Variation of Benzazole-Substituted 8-Hydroxyquinolines

A series of structurally related bistridentate heteroleptic Ru(II) polypyridyl complexes, [RuII(ttpy)(8-HQLS/N/O)]+ (Ru1-Ru3), were synthesized, where ttpy = p-tolyl terpyridine and 8-HQLS/N/O are monoanionic N^N^O-donor tridentate ligands (8-HQLX), derived from 8-hydroxyquinoline (8-HQ), namely, 8-HQLS = 2-(2'-benzothiazole)-8-hydroxyquinoline, 8-HQLN = 2-(2'-benzimidazole)-8-hydroxyquinoline, and 8-HQLO = 2-(2'-benzoxazole)-8-hydroxyquinoline. The electronic structures of these rigid ligands were systematically tuned by varying the noncoordinating heteroatoms (S, O, NH) in the five-membered heterocyclic ring, impacting the electronic properties, redox potentials, excited-state lifetime/dynamics, and deactivation pathways and photophysical behavior of the corresponding Ru(II) complexes. Notably, [RuII(ttpy)(8HQLN)]+ (Ru2) exhibited an excited-state lifetime (τ > 1 ns in CH3CN at RT) surpassing that of the homoleptic complex [Ru(ttpy)2]2+ (τ ∼ 0.62 ns), despite its more distorted octahedral geometry. These heteroleptic complexes (Ru1-Ru3) showed extended excited-state lifetimes compared to their homoleptic counterpart Ru4. The complexes displayed absorption in the red region, which is favorable for phototherapeutic applications. Their relative singlet oxygen (1O2) quantum yields (ΦΔ) in CH3CN ranged from 0.03 to 0.10. Given their reasonable excited-state lifetimes and 1O2 generation ability, these Ru(II) complexes demonstrated potential as photocatalysts for organic substrates, as evidenced by their effectiveness in the photooxidation of PPh3 to Ph3P=O as a model reaction.

A Tetranuclear NiII 4O4 Cubane Molecular Complex as an Efficient Electrocatalyst for Oxygen Evolution Reaction: From Synthesis to Mechanistic Insights

The oxygen evolution reaction (OER) is integral to electrochemical energy systems; however, its intrinsic sluggish kinetics necessitate the design of high-performance electrocatalysts to minimize overpotential, enhance the durability, and optimize the efficiency. Significant efforts have been dedicated to developing OER catalysts based on earth-abundant transition-metal complexes. Here, the efficacy of a tetranuclear cubane-cored Ni(II) complex, [Ni₄(LH)₄(MeOH)]·CHCl₃ (1), in OER is demonstrated. The complex is synthesized using a tetradentate Schiff-base ligand, [2-{(E)-(2-hydroxyphenylimino)methyl)-6-(hydroxymethyl)-4-methylphenol}], and characterized by single-crystal X-ray diffraction. The redox properties of complex 1 are evaluated by cyclic voltammetry in the solid state, which emphasize the quasireversible oxidation state of the Ni(II) metal center. The complex 1 is immobilized on activated carbon cloth (CC), referred as CC-1, which demonstrates efficient OER catalysis, subsequently activating to form the Ni(O)OH catalyst. The postreaction analysis including UV-vis, FTIR, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy confirm the stability of molecular complex 1. The results demonstrate efficient OER catalysis with a low overpotential of 330 mV versus reversible hydrogen electrode and a Tafel slope of 64 mV dec-1, confirming an effective OER catalyst in alkaline medium with a deep understanding of the core reaction mechanisms.

Probing the Framework Metal Dependent Properties of Actinide-Centered Polyoxoalkoxide Sandwich-Type Complexes

Development of a simple and scalable synthesis of (TBA)3[W5O18MoNO] provides for the formation of the mixed-metal lacunary polyoxoalkoxide, (TBA)2[W4O13(OMe)4MoNO][Na(MeOH)]. This complex was used to synthesize a series of polyoxoalkoxide sandwich-type complexes with the general formula (TBA)2[M{W4O13(OMe)4MoNO}2], where M = Zr(IV), Hf(IV), Th(IV), U(IV), and Np(IV). Compared to the analogous all-molybdenum complexes, the series have drastically different optical and redox properties. The results indicate that framework metal substitution acts as a tool for "orbital engineering", with Density Functional Theory (DFT) calculations revealing that the major consequence of incorporation of tungsten into the complexes is localization of LUMO and LUMO+1 on the molybdenum centers remaining in the molecule. The change in the distribution of the frontier orbitals translates to discrepancies in the electronic properties of the series. Given the rarity of polyoxometalate complexes featuring a U(V) ion, one electron oxidation of (TBA)2[U(IV){W4O13(OMe)4MoNO}2] was pursued. Isolation of the corresponding U(V) centered sandwich-type complex is reported, only the second example of U(V)-polyoxometalate complex described to date.

Support for the Anticipated Binding Mode of a Cytotoxic Dinuclear Copper Complex to Two Neighboring Phosphate Esters of the DNA Backbone

The cytotoxic dinuclear complex [(Htom6-Me){CuII(OAc)}2](OAc) (H2tom6-Me = 2,7-bis(di(6-methylpyridine-2-yl-methyl)aminomethyl)-1,8-naphthalenediol) binds to DNA, interferes with DNA synthesis in PCR at lower concentrations than cisplatin, and kills human cancer cells more efficiently than human stem cells of the same proliferation rate. It is supposed that the OAc- ligands dissociate in aqueous buffer, providing [(Htom6-Me){CuII(OH2)}2]3+, while the fragment [(Htom6-Me)CuII2]3+ binds to two neighboring phosphate diesters of the DNA backbone. Here, we report the hydrolysis of [(Htom6-Me){CuII(OAc)}2](OAc) in phosphate buffer providing the anticipated [(Htom6-Me){CuII(OH2)}2]3+. Moreover, the same reaction in H2O/CH3OH yields the complex [(Htom6-Me){CuII(H2PO4)}2]+. The molecular structures of [(Htom6-Me){CuII(OH2)}2]3+ and [(Htom6-Me){CuII(H2PO4)}2]+ show different coordination modes around the CuII ions demonstrating a significant flexibility of the fragment [(Htom6-Me)CuII2]3+ for binding to exogenous ligands despite its rigid naphthalene backbone. The coupling is weakly antiferromagnetic in [(Htom6-Me){CuII(H2PO4)}2]+, while that in tricationic [(Htom6-Me){CuII(OH2)}2]3+ is weakly ferromagnetic and can be attributed to the orthogonal orientation of the basal planes. UV-vis-NIR spectra of [(Htom6-Me){CuII(H2PO4)}2]+ but also of [(Htom6-Me){CuII(OAc)}2](OAc) in aqueous solution resemble that of [(Htom6-Me){CuII(OH2)}2]3+ demonstrating our earlier assumption that [(Htom6-Me){CuII(OH2)}2]3+ is the active species in buffer solutions for interaction with DNA. Moreover, the exchange of the OAc- ligands by H2PO4- ligands models the anticipated binding of [(Htom6-Me){CuII(OH2)}2]3+ to the phosphates of DNA.

Luminescent Indium Dicyanoaurate Coordination Polymers with Short Aurophilic Interactions

A series of coordination polymers were synthesized by combining In(OTf)3 (OTf = trifluoromethanesulfonate), 2,2';6',2"-terpyridine (Terpy) or its substituted analogues 4'-amino-2,2';6',2"-terpyridine (NH2-Terpy), 4'-chloro-2,2';6',2"-terpyridine (Cl-Terpy), and 4'-bromo-2,2';6',2"-terpyridine (Br-Terpy), with K[Au(CN)2]. All compounds consist of 1D chains of hydroxy-bridged [In2(OH)2(X-Terpy)2]4+ dimers connected to a 1D chain of [Au(CN)2]- units featuring very short aurophilic interactions (3.0106(3)-3.2155(4) Å). The distance of the aurophilic interaction is directly tunable through minor modifications of the ligand, with the Au(I)···Au(I) distance increasing as the size of the substituent on the Terpy ligand increases. The compounds display photoluminescence emission maxima ranging from 600 to 650 nm, which are significantly lower energy than for most [Au(CN)2]--based materials. The emission maxima shift to higher energy as the aurophilic interactions become longer. These results demonstrate the ability to tune the Au(I)···Au(I) distance, and in turn the luminescence, by varying the size of the substituent on the chelating ligand.

A Molecular Planetarium: Evidence for an Iodide Ligand Orbiting Two Gold(I) Ions in the Luminescent Cation, [Au2(μ-1,2-Bis(diphenylphosphino)methane)2I]. Inorg Chem 2025;64:9002-9013. [PMID: 40298146 DOI: 10.1021/acs.inorgchem.5c00396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Four new crystalline gold(I) complexes, [Au2(μ-dppm)2I][Au2(μ-dppm)2(μ-I)](AsF6)4·4CH2Cl2 (1), [Au2(μ-dppm)2(μ-I)]I·2CH2Cl2 (2), [Au2(μ-dppm)2(μ-I)](PF6)·CH2Cl2 (3), and [Au2(μ-dppm)2](AsF6)2·CH2Cl2 (4) where dppm is bis(diphenylphosphino)methane) have been prepared and structurally characterized by single crystal X-ray diffraction and nuclear magnetic resonance spectroscopy (NMR). Yellow crystals of [Au2(μ-dppm)2(μ-I)]I·2CH2Cl2 (2) and [Au2(μ-dppm)2(μ-I)](PF6)·CH2Cl2 (3) have a structure with two three-coordinate gold(I) ions held in close proximity by the dppm and bridging iodide ligands. Crystals of [Au2(μ-dppm)2I][Au2(μ-dppm)2(μ-I)](AsF6)4·4CH2Cl2 (1) have two different cations: one similar to complexes 2 and 3 and the other cation with a terminal iodide ligand in an unusual arrangement that binds a two-coordinate gold(I) ion to a three-coordinate gold(I) ion through an aurophilic interaction. In contrast, [Au2(μ-dppm)2](AsF6)2·CH2Cl2 (4) has no anion bound and only has the gold ions as two-coordinate centers. Each complex displays luminescence under UV irradiation in the solid and solution states. Remarkably, the NMR spectra of solutions of the iodide complexes (1), (2), and (3) suggest that the iodide ion is bound to the [Au2(μ-dppm)2]2+ core but is able to circulate around this core.

Borate Salts of Aluminum-Alkyl Cations Stabilized by P-, O-, and C-Donors: Synthesis, Characterization and Application as Cocatalysts

Well-defined Al-alkyl borate (AAB) salts {[iBu2(L)Al]2(μ-H)}+[B(C6F5)4]- (AlHAl_L) with L = N-donor ligands have been recently reported as promising "complete" cocatalysts for olefin polymerization. Herein, we explore structural variations of AlHAl_L going beyond the class of N-donors like the prototypical N,N-dimethyl aniline (DMA). Thirteen P-, O-, and C-donor ligands were screened, allowing isolation of AAB salts with mono- and bidentate phosphines, alkyl-, aryl-, and silyl-ethers, and a N-heterocyclic carbene. Except for the diphosphine with the longest spacer between the P atoms [bis(diphenylphosphino)hexane, DPPH], all donors gave well-defined tetracoordinate or tricoordinate molecular species, which were characterized in solution (NMR) and solid state (XRD), and tested as cocatalyst in ethylene/1-hexene copolymerization with an ansa-zirconocene catalyst [rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2]. The vast majority of novel AAB salts provided active catalytic systems, further demonstrating the broad tunability of these species. Consistent with previous studies, variability in productivity upon L variation is primarily related to the efficiency of precatalyst activation, determining the fraction of Zr active sites. Variations in polymer molecular weight and comonomer incorporation observed with some P-, O- and C-donor ligands indicate that also interactions between the L donors and the Zr active species might be relevant in determining catalytic performance in some cases.

Redox-driven photoselective self-assembly

Self-assembly via non-covalent interactions is key to constructing complex architectures with advanced functionalities. A noncovalent synthetic chemistry approach, akin to organic chemistry, allows stepwise construction with enhanced control. Here, we explore this by coupling Pt(II) complex self-assembly with a redox reaction. Oxidation to Pt(IV) creates a non-emissive monomer that, upon reduction to Pt(II), forms luminescent gels with unique kinetic and thermodynamic pathways. UV irradiation induces Pt(IV) reduction, generating supramolecular fibers with Pt∙∙∙Pt interactions, enhancing photophysical properties and enabling visible light absorption up to 550 nm. This allows photoselective growth, where fibers convert surrounding Pt(IV) to Pt(II), promoting growth over nucleation, as observed via real-time fluorescence microscopy.

Exploring the energetic potential of 2,5-disubstituted tetrazoles: a case of 2,5-bis(oxadiazolyl)tetrazoles

Exploration of new possible molecular combinations for the preparation of energetic materials remains a challenging task. Herein, the construction of new azole assemblies incorporating the poorly studied 2,5-disubstituted tetrazole motif in combination with oxadiazole moieties is presented. A complete set of experimentally defined properties including thermal stability and mechanical sensitivity, as well as the calculated detonation performance, was evaluated. All target energetic substances have high densities (1.72-1.74 g cm-3) and high combined nitrogen-oxygen content (55-73%). Azo-bridged hexaheterocyclic entities showed high friction sensitivity (on the level of primary explosives), while the introduction of two amino groups improved the sensitivity up to a nitro ester's level, considered as the lowest acceptable level for manufacturing.

Self-Assembly and Dynamic Equilibrium of Trinuclear and Tetranuclear Cu(I) Supramolecules Featuring nido-Carborane-Supported N-Heterocyclic Carbene Ligands

The self-assembly of metallo-supramolecules has attracted considerable attention in recent decades. These discrete architectures are primarily driven by coordination interactions, typically involving M-N/O (Werner-type) or M-C (organometallic) bonding. However, the use of M-π interactions for constructing these multinuclear complexes remains largely unexplored. In this work, we report the self-assembly of trinuclear and tetranuclear copper(I) complexes driven by a combination of M-π and M-C coordination interactions. These multinuclear Cu(I)-NHC complexes were synthesized from the nido-carborane-supported N-heterocyclic carbene (NHC) precursors and Cu(I) ions. In solution, a dynamic equilibrium between the trinuclear and tetranuclear species was observed, as confirmed by the variable-temperature NMR spectrum. Van't Hoff analysis revealed that the equilibrium is endothermic (ΔHeq = 53.6 kJ mol-1) and entropically driven (ΔSeq = 158 J mol-1 K-1). The solid-state structures of both forms were elucidated through single-crystal XRD analysis. Density functional theory calculations showed that the Cu-CNHC bonds in these complexes are relatively weak (∼100 kJ mol-1, approximately one-third of the strength of typical Cu-CNHC bonds). This is attributed to the strong Coulombic attraction between positively charged Cu(I) and negatively charged nido-carborane ligands (M-π interactions), which significantly reduces the bond strength between Cu(I) and neutral NHC moieties (M-C bonding).

Circularly Polarized Luminescence From Spontaneous Symmetry Breaking in a Bimetallic Eu-Al Complex

The emergence of optically active functional compounds through spontaneous chiral symmetry breaking is a rare but intriguing phenomenon with relevance of both practical and fundamental interest. Here we show that a racemic Eu-Al compound, bearing only non-chiral ligands, forms a conglomerate upon crystallization. Single crystals of the compound are electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) active. Moreover, we found that a significant enantiomeric excess (50%) of either enantiomer is present in each crystallization batch (non-racemic conglomerate). Such spontaneous symmetry breaking leads not only to optically active single enantiomorph crystals but to an overall solid bulk with significant ECD and CPL.

Exploring Tyramine's Role in the Formation of Supramolecular Adducts with Nonsteroidal Anti-Inflammatory Drugs

In pharmaceutical crystal engineering, salification and co-crystallization are well-established strategies to enhance the physicochemical properties of nonsteroidal anti-inflammatory drugs (NSAIDs), which typically exhibit low aqueous solubility. This study introduces three new multicomponent crystalline systems of NSAIDs (S-naproxen, flurbiprofen, and ketoprofen) with the co-former tyramine, designed using knowledge-based methods. Additionally, a new polymorph of the diflunisal-tyramine system, synthesized via mechanochemical techniques, is reported. The new multicomponent systems were thoroughly characterized using solid-state NMR and single-crystal X-ray diffraction. Aqueous solubility tests conducted through solution 1H NMR experiments revealed increased equilibrium solubility for all samples, highlighting the efficacy of crystal engineering in modulating the physicochemical properties of drugs.

Oxidation-Deformylation Cascade Catalyzed By a Mononuclear Copper Complex

In this study, two copper complexes were synthesized using N3 (arising from two pyridines and one amide group) containing ligands N-(2-picolyl)picolinamide (L1H) and bis(2-pyridylcarbonyl)amine (L2H), forming [(L1)CuII(OH2)(NO3)] (1) and [(L2)CuII(OH2)2](NO3) (2). The reaction of complex 1 with hydrogen peroxide in alcoholic solvents yielded a formate-bound complex. Studies with isotopically labeled 13C ethanol indicated that formate originates from the C1 of ethanol after C-C bond cleavage. Complex 1 was found to catalytically convert primary alcohols into formic acid probably following a two-step process: (i) alcohol oxidation to aldehyde and (ii) aldehyde deformylation. Further experiments with 2-phenylpropionaldehyde (2-PPA) confirm the ability of complex 1 to catalyze aldehyde deformylation. Both steps of the reaction are associated with significant kinetic deuterium isotope effects (KDIE), suggesting that hydrogen atom abstractions (HAA) occur during the rate-determining steps of both conversions. Overall, this system proposes a clean catalytic process for alcohol-to-formic acid conversion, operating under mild conditions, and offering potential synthetic applications.

Thermoresponsive Behaviors of Poly(N-methacryloyl glycinamide) and Poly(N-acryloyl glycinamide): Effect of Methacrylation

Poly(N-acryloyl glycinamide) (PNAGA) proves to be an interesting and useful polymer with an upper critical solution temperature (UCST) behavior in water due to intra- and intermolecular hydrogen bonding. Its methacrylamide counterpart, poly(N-methylacryloyl glycinamide) (PNMAGA), has a different UCST behavior, which is easier to dissolve in water. In this work, PNMAGA and PNAGA were synthesized by RAFT polymerization and free radical polymerization, and their solution properties in dilute aqueous media have been studied and compared in detail to elucidate the effects of temperature, polymer concentration, molecular weight, and chain end. The direct comparison provides a better understanding of the UCST behaviors. The presence of an extra methyl group on the repeating unit helps the polymer to dissolve better and eliminates the need for special thermal treatment to obtain a complete dissolution. Infrared spectroscopy and X-ray diffraction analysis show variation in hydrogen bonds between the two polymers and their respective monomers, providing insights into the structural origin of their different solution properties.

The Role of Lithium Ions on the Solubility of K4E4 in Ethylenediamine and the Oxidation of the Zintl Anions [E4]4- (E = Ge, Sn, Pb) as well as [Ge9]4

Zintl phases are excellent precursors for nine atom [E9]4- clusters, which are readily accessible by dissolution of A4E9 phases (A = Na-Rb; E = Ge-Pb) in ethylenediamine (en). In contrast, the binary alkali-metal tetrel phases of composition A4E4 are insoluble in en. Furthermore, Li+ cations are rarely investigated as counterions for tetrel element Zintl clusters. We report here that K4E4, comprising [E4]4- polyanions (E = Ge, Sn, and Pb), which are insoluble in en, readily dissolves in en in the presence of lithium ions and the four atomic polyanions [E4]4- are oxidized to nine-atom [E9]4- clusters during dissolution. We isolated crystals of [Li(en)2.5]4[Ge9] and [Li(en)2]4[E9] (E = Sn and Pb) with exclusively Li counterions. Furthermore, the alkali-metal ion exchange of K4Ge9 with LiCl in en results also in the oxidation of [Ge9]4- to [Ge9-Ge9]6- dimers which were isolated as partially and fully ion-exchanged salts such as K2[Li(en)2]4[Ge9-Ge9] and [Li(en)2]6.5[Ge9-Ge9], respectively. NMR spectroscopic investigations of solutions of [Sn9]4- that contain variable Li:K ratio reveal contact K+/[Sn9]4- ion pairs, while Li+ ions form solvent-separated ion pairs. The role of Li+ ions on the solubility of Zintl phases and Li+ assisted oxidation of Zintl ions is highlighted.

An Anthracene Derivative with a Highly Vertical Molecular Orientation

Controlling the orientation of the transition dipole moment (TDM) is very important in the field of optoelectronics. In particular, the horizontal orientation of emissive TDMs in organic materials has been extensively studied because it can improve the out-coupling efficiency of organic light-emitting diodes (OLEDs). Conversely, the vertical orientation of emissive TDMs remains virtually unexplored. Using angle-dependent photoluminescence measurements, we discovered that 9,10-bis(3,5-dimethoxyphenyl) anthracene (DMA) shows an extremely high vertical emissive TDM orientation (ΘV) of 82% in an evaporated neat film. To the best of our knowledge, this is the highest value reported so far for organic molecules. To investigate the origin of the high ΘV value, we conducted two-dimensional grazing-incidence wide-angle X-ray scattering measurements (2D GIWAXS) on a DMA film and observed distinct periodic peaks in the out-of-plane direction. By combination of these measurements with single-crystal X-ray diffraction analysis, the periodic peaks were identified as lamellar structures in which DMA molecules are stacked with their long molecular axes oriented vertically on a quartz substrate. Moreover, by virtue of the exceptionally high vertical TDM orientation, the DMA film exhibits highly polarized emission from the substrate edge. We also investigated the TDM orientation of other 9,10-diphenylanthracene derivatives and observed random or horizontal TDM orientations in all cases, which highlights the uniqueness of the vertical orientation of DMA.

Diverse redox-mediated transformations to realize the para-quinoid, σ-bond, and ortho-diphenoquinoid forms

π-Electron systems with multiple redox-active units have attracted attention in various fields due to their potential applications. However, the design strategy remains elusive to selectively synthesize the diverse molecular structures of redox-convertible species. In this study, covalently linked quinodimethane derivatives with a sulfur bridge [(Ar4QD)2S] were designed as redox-active motifs that can be converted into three different geometries via redox reaction. Here we show that the favored geometry of the corresponding redox states of (Ar4QD)2S can be precisely controlled by adjusting the steric bulk of the substituents on the aryl group to change the proximity of the quinodimethane units. Notably, this redox-mediated strategy also leads to the isolation and structural determination of the missing link with an o-diphenoquinoid structure, a diphenoquinoid isomer whose isolation had remained elusive for almost a century. Thus, this study provides a method that allows the modulation/control of electronically and/or thermodynamically stable structures, as well as their electronic and spectroscopic properties.

The Dinuclear Zirconocene Complex [(Cp2Zr)2(μ-Me)(μ-C2Ph)] as a Platform for Small Molecule Activation

The dinuclear title compound [(Cp2Zr)2(μ-Me)(μ-C2Ph)] 5 was prepared from a zirconocene alkynyl methyl complex and Rosenthal's zirconocene source [Cp2Zr(py)(η2-Me3SiC2SiMe3)] in a formal comproportionation reaction. This complex shows catalytic activity for the dehydrocoupling of amine boranes, with a dinuclear hydride-bridged alkynyl complex 6 being formed as a catalytically relevant species. The structure of this complex was confirmed for the first time by single-crystal X-ray analysis. The reaction of complex 5 with hydrogen results in hydrogenation of the alkynyl ligand, yielding a highly labile trinuclear hydride-bridged complex as a possible intermediate of zirconocene dihydride/ethylbenzene formation. This complex shows an unusual distorted planar tetracoordinate environment at the central carbon atom positioned between the three Zr centers. The reaction of complex 5 with 2-cyanopyridine and acetonitrile is characterized by a reduction of the substrates. The herein reported reactivity of complex 5 demonstrates the remarkable potential of well-established dinuclear zirconocenes to stabilize unusual bond situations, which were analyzed comprehensively using spectroscopic, structural, and computational methods.

Synthesis and characterization of a novel copper carboxylate complex and a copper complex-coated polyether sulfone membrane for the efficient degradation of methylene blue dye under UV irradiation: single crystal X-ray structure of the copper carboxylate complex

This study presents the synthesis of a novel binuclear Cu(II) carboxylate complex under ambient laboratory conditions. The complex possesses a paddle wheel structure in which the axial positions are occupied by bromide/nitrate ligands. The synthesized complex was characterized using single-crystal X-ray crystallography, FT-IR, X-ray diffraction, and UV-Visible spectroscopic techniques. The thermal stability of the metal complex was studied through thermogravimetric analysis. The synthesized metal complex was employed for the synthesis of metal complex-coated polyether sulfone (PES) membranes, which were characterized before and after filtration using the FESEM technique. The photocatalytic efficiency of the metal complex for the degradation of methylene blue dye under UV irradiation in the presence of H2O2was studied and compared with the photodegradation efficiency of the metal complex-coated polyether sulfone (PES) membrane.

Gold bis(dithiolene) radical with fused pyrazine and dithiine rings on dithiolene ligand turns metallic under pressure

Conducting molecular materials built on dithiolene complexes, as mixed-valence salts or single component materials, are most often based on planar structures which efficiently stack on top of each other. Herein, we report an original dithiolene ligand, namely, [1,4]dithiino[2,3-b]pyrazine-2,3-bis(thiolate) (hereafter noted as pzdtdt), which combines an electron-withdrawing pyrazine ring and a folded (by 40-50°) dithiine ring. Until now, such strong distortions from planarity have been hindering the isolation of highly conducting materials from dithiine-containing dithiolene complexes. However, in this study, we showed that the gold complex radical [Au(pzdtdt)2]˙ obtained via electrocrystallization from the 1e- oxidation of [Ph4P][Au(pzdtdt)2] organized into regular, non-dimerized chains in the solid state. Interestingly, [Au(pzdtdt)2]˙ exhibited a semi-conducting behaviour at ambient pressure and turned metallic upon application of pressures above 4 GPa. The electronic structure of [Au(pzdtdt)2]˙ was investigated in terms of electron localization effects through spin-polarized band-structure calculations.

Dual magnetic behavior of an Fe(III)-dioxolene complex with tri-substituted catechol

Magnetically bistable compounds attract considerable attention due to their possible applications in molecular electronics and spintronics devices. Of special interest are spin-crossover (SCO) systems that can interconvert between the low-spin and high-spin states leading to switching of the magnetic properties. Synthesis and comprehensive characterization of a family of ionic ferric-dioxolene complexes [(TPA)Fe(HO-DBCat)]ClO4 (1), [(TPA)Fe(NO2-DBCat)]ClO4 (2) and [(TPA)Fe(MeOCH2-DBCat)]ClO4 (3) (TPA = tris(2-pyridylmethyl)amine; HO-DBCat = dianion of 4,6-di-tert-butyl-1,2,3-trihydroxybenzene, NO2-DBCat = dianion of 4,6-di-tert-butyl-3-nitro-1,2-dihydroxybenzene and MeOCH2-DBCat = dianion of 4,6-di-tert-butyl-3-methoxymethyl-1,2-dihydroxybenzene) are reported. Variable temperature structural, magnetic and spectral analyses revealed that compounds 1-3 undergo a thermally induced SCO in the solid state between the high-spin (S = 5/2) and low-spin (S = 1/2) states. Alternating current magnetic susceptibility measurements indicated that the nitro-substituted complex 2 shows a field supported slow magnetic relaxation in the low-spin state at 5000 Oe. Such duality of magnetic properties makes complex 2 the first ferric compound which demonstrates a complete S = 5/2 → S = 1/2 SCO with a single molecule magnet behavior (SMM, S = 1/2). Electronic structures and magnetic properties of 1, 2 and 3 were investigated with the aid of DFT and SA-CASSCF/NEVPT2 calculations.

Revisiting Fused-Pyrrolo-1,10-Phenanthroline Derivatives: Novel Transformations and Stability Studies

In this study, new pyrrolo[3',4':3,4]pyrrolo[1,2-a][1,10]phenanthroline derivatives are developed and their stabilities and transformation pathways are investigated. The synthetic approach toward these novel derivatives include a pivotal [3 + 2] cycloaddition of in situ generated ylides, followed by cycloadducts oxidation and other unexpected transformations. The structures of the intermediate and final compounds are proposed based on information obtained from several spectral techniques. Stability study reveal that electron-donating groups in the para position of the phenyl ring promote easier oxidation, whereas electron-withdrawing substituents enhance the stability of the compounds. The acid-base titration of α-monosubstituted 1,10-phenanthroline 6a results in a reversible color change, which is preliminarily explored through spectral methods.

Tungsten oxide as a universal source for the synthesis of complexes with different nuclearities in WO3/chalcogen/NaCN systems

Tungsten trioxide can be used as a readily available source in the one-step preparation of a variety of cyanide and chalcocyanide mononuclear and cluster complexes of tungsten. In our study of phase formation in the system 6WO3 + 8Q + 32NaCN (Q = S, Se or Te) in the temperature range of 250-700 °C, we determined which soluble complex compounds are formed, the temperature limits of their existence and the influence of synthesis time on the composition of the products. As the temperature increases, the process begins with the formation of mononuclear and then cluster complexes and ends with the formation of tungsten dichalcogenides: [W(CN)8]4- → [WS4]2-/[WS3O]2- → [{W3Q4}(CN)9]5- (Q = S or Se), [{W3S3O}(CN)9]5- → [{W4Q4}(CN)12]6- (Q = S, Se or Te) → WQ2 (Q = S or Se). Depending on the synthesis conditions, these complexes can either coexist in a mixture or one of them becomes the main product of the reaction. The obtained trinuclear and tetranuclear cluster complexes were studied by 13C, 77Se and 183W NMR spectroscopy using DFT calculations to assign the spectral signals. The crystal structures of the salts Cs5Na3[W(CN)8]2·2H2O (1), Cs2.8Na2.2[{W3S4}(CN)9]·2.2H2O (2), Cs5[{W3S3O}(CN)9]·2H2O·0.5CsCl (3) and Cs3.5Na1.5[{W3Se4}(CN)9]·6.5H2O (4) were determined by single-crystal X-ray diffraction analysis. It was also revealed that the quantitative ratio of trinuclear complexes [{W3S3O}(CN)9]5- and [{W3S4}(CN)9]5- with different cluster core compositions formed in the 6WO3 + 8S + 32NaCN system at 300 °C depends on the synthesis time. Dynamics of the observed transformation of the initially dominant complex with a heteroleptic cluster core {W3(μ3-S)(μ-S)2μ-O} into the complex with a homoleptic core {W3(μ3-S)(μ-S)3} was studied using 13C NMR spectroscopy.

(C5N2H7)IO2F2 and (C3N6H8)(IO2F2)2: two new organic-inorganic hybrid fluoroiodate birefringent crystals

Birefringent crystals are anisotropic materials commonly used in modern optical devices to obtain polarized light. The traditional commercial birefringent crystals, such as MgF2 and CaCO3, have low birefringence and are not easy to grow. Herein, two organic-inorganic hybrid birefringent crystals composed of π-conjugated organic groups and lone pair-containing (IO2F2)- anions, namely, (C5N2H7)IO2F2 and (C3N6H8)(IO2F2)2, were successfully grown by a simple evaporation method. In their structures, the π-conjugated organic cations and (IO2F2)- anions are interconnected through hydrogen bonding and π-π stacking interactions into 3D supramolecular networks. Both of them exhibit large birefringence values of 0.30 @ 550 nm and 0.23 @ 550 nm, which are superior to the values of most of the conventional birefringent materials. Moreover, UV-vis-NIR diffuse reflectance spectra demonstrate that they have wide band gaps (4.06 eV and 4.10 eV) because of the presence of the F element with strong electronegativity. Theoretical analyses suggest that the parallel arrangement of the π conjugated cations resulted in large optical anisotropy. This work provides new promising candidates for UV birefringent materials.

Different mechanisms for lanthanide(III) sensitization and Yb-field-induced single-molecule magnet behaviour in a series of pentagonal bipyramidal and octahedral lanthanide complexes with axial phosphine oxide ligands

Seven mononuclear lanthanide complexes have been isolated and structurally characterised. Four of them are cationic, whose charges are balanced by chloride counteranions, and exhibit pentagonal bipyramidal coordination geometry, whereas the rest of them are neutral and display octahedral coordination environment. In all cases, the coordination sphere of the LnIII ions consists of two di(1-adamantyl)benzylphosphine oxide ligands in axial positions, whereas in the equatorial plane the former contains a chloride and four water molecules and the latter a solvent molecule and three chloride ligands. We report a detailed photophysical investigation, including time-dependent density functional theory (TD-DFT) calculations and intramolecular energy transfer (IET) analysis, which reveals two distinct lanthanide sensitization mechanisms. Compound-specific energy transfer pathways occur through either the S1 or T1 states, as supported by calculated IET rates and resonance with lanthanide acceptor transitions. In addition, dc and ac magnetic properties were measured on complexes 1 and 2, showing that compound 1 behaves as a bi-functional compound, exhibiting field-induced single molecule magnet behaviour together with YbIII-centred NIR luminescence. The relaxation of the magnetization in this pentagonal bipyramidal complex takes place through Raman and direct processes, as supported by ab initio calculations.

Crystal Structure and Low-Dimensional Magnetism in CsNiV2O6Cl

Single crystals of CsNiV2O6Cl were grown hydrothermally. Its crystal structure (space group I2̅/a) is based on vertex-sharing twisted chains of Ni2+O4Cl2 octahedra and edge-sharing chains of V5+O5 tetragonal pyramids. These chains running along the c- and a-axes, respectively, link, forming an open framework with Cs ions in the voids. At elevated temperatures, the temperature dependence of dc magnetic susceptibility evidences a Haldane-type behavior with estimated intrachain exchange interaction J = 267 ± 16.5 K followed by the strong upturn at lower temperatures. Both dc and ac magnetic susceptibilities exhibit a sharp peak at low temperatures; the latter is independent of frequency. The position of the peak in Fisher's specific heat d(χT)/dT coincides with that in specific heat Cp, which defines the Neel temperature TN = 5.6 ± 0.2 K. While the values of the calculated interchain exchange interaction J' and single-ion anisotropy D place this system into the Haldane sector of the Sakai-Takahashi phase diagram, the long-range antiferromagnetic order at low temperatures is induced by the defects/impurities.

Facile synthesis of acridine-based nickel(II) complexes via metal-mediated rearrangement of diphenylamine derivative and application in H2 evolution reaction

In this study, the formation of acridine-based metal complexes from rearrangement of diphenylamine-2,2'-dicarboxaldehyde (2,2'-dpadc) in the presence of transition metal ions was investigated. As a result, two novel isomorphic nickel(II) complexes bearing acridine-based Schiff-base ligand [NiLACR](X)2·CH3CN (X = BF4 (1), ClO4 (2), LACR = (E)-N1-(2-((acridin-4-ylmethylene)amino)ethyl)-N1-(2-aminoethyl)ethane-1,2-diamine) were successfully synthesized via a one-pot condensation of 2,2'-dpadc and tris(2-aminoethyl)amine (TREN) with a satisfactory yield of approximately 60%. These complexes were fully characterized by X-ray crystallography, UV-vis spectroscopy and CHN elemental analysis. Additionally, their thermal stability (thermogravimetric analysis) and electrochemical properties were also determined. A plausible mechanism for the nickel(II)-mediated rearrangement of 2,2'-dpadc to form the acridine-based nickel(II) complex was proposed. To demonstrate their potential applications, complex 1 was explored in the realm of electrocatalysis. It exhibited moderate activity towards hydrogen evolution reaction (HER). During 1-h controlled-potential electrolysis (CPE) experiments, H2 production (16 micromole) was observed with faradaic efficiency of 40% when the reaction was conducted in a TBAPF6/DMF solution at -2.1 V vs. Fc/Fc+ in the presence of acetic acid as a proton source. The facile synthesis of these acridine-based nickel(II) complexes reported herein may stimulate further development of novel acridine-based ligands and their corresponding metal complexes for a wide range of applications.

Hydrogen-Bond-Assisted Chalcogen Transfer between Phosphine Selenides and Arsine Oxides

The Brønsted acid catalysis is widely regarded as one of the most effective methods for activating inert substrates and enabling unique reactivity. In this work, we introduce the first example of H-bond-assisted chalcogen exchange between arsine oxides and phosphine selenides under mild conditions, providing a powerful approach to the synthesis of arsine selenides. The reaction proceeds successfully in both protic and aprotic solvents and is accelerated by the presence of any nonaqueous acid. This newly discovered reaction is tested for various arsine oxides R3AsO (R = Ph, Et, nBu, iPr) and phosphine selenides R3PSe (R = Ph, Me, Et, tBu) and overall demonstrates high conversion, although the use of reagents with bulky substituents significantly hinders its efficiency. The reaction mechanism involves the formation of a four-membered cyclic transition state, which requires overcoming steric and electrostatic repulsion, as well as significant distortion of the reagents' tetrahedral geometry. Hydrogen bonding with the As═O fragment helps to reduce electrostatic repulsion between the P═Se and As═O groups, making the formation of the cyclic intermediate more favorable.

A Study on the [3+2] Cycloaddition Reaction of Square Planar Ni(II) Azido Complexes: Structure, Properties, and Catalytic Applications of the Products

Two square planar Ni(II) azido complexes [Ni(N3)(L1)] and [Ni(N3)(L2)] (where L1 = N-phenyl-2-(pyridin-2-ylmethylene)hydrazine-1-carbothioamide; L2 = (E)-1-(((2-(diethylamino)ethyl)imino)methyl)naphthalen-2-olato) were used to study the effect of auxiliary ligands on the [3+2] cycloaddition reactions with different dipolarophiles. The reactivity of the complex [Ni(N3)(L1)] was greater than that of the complex [Ni(N3)(L2)]. [Ni(N3)(L1)] gives an N2-triazolato product with an electron-deficient alkyne R1─C≡C─R2 with R1 = R2 = COOCH3, COOEt, or R1 = CF3, R2 = COOEt while [Ni(N3)(L2)] gives a homobimetallic bis(μ-NN'-triazolato) bridged product only with F3C─C≡C─COOEt. The complex [Ni(N3)(L2)] reacts with dialkyl acetylene-dicarboxylate alkyne, yielding N1-triazolato products under strictly anhydrous conditions, whereas the same reaction under ambient conditions yielded a new unexpected octahedral complex in which the alkyne is converted into a novel O, O donor bidentate ligand. The nature of the predominant triazolato isomer (N1/N2) was experimentally confirmed by single-crystal X-ray diffraction analysis and also verified by DFT calculations. [Ni(N3)(L1)] gives a homobimetallic bis(μ-tetrazolato) bridged product by the [3+2] cycloaddition reaction of 2-cyanopyridine and 2-cyanopyrimidine. [Ni(N3)(L1)] also underwent a 1,3-dipolar cycloaddition with phenyl isothiocyanate at room temperature, giving the corresponding tetrazolato-thione complex, while the same reaction with [Ni(N3)(L2)] does not proceed. Both complexes give Ni(II) isothiocyanate complexes by the reaction of carbon disulfide. The catalytic activities of all the Ni(II) complexes were evaluated for the synthesis of 2-amino-3-cyano-4H-pyran derivatives. [Ni(triazolateCOOMe,COOMe-N2)(L1)] (complex 3) emerged as a highly efficient catalyst, demonstrating performance significantly superior to previously reported catalysts at room temperature. 0.0001 mol % catalyst loading is sufficient to obtain the product, and the highest turnover number (680000) and turnover frequency (34000 min-1) were achieved.

Expanding the Toolbox: Synthesis of Zintl Salts Containing Anions of the In/Sb and Tl/Sb Elemental Combinations

Binary Zintl anions comprising atoms of two p-block elements, and ternary Zintl clusters, in which the latter are combined with d-/f-block metal ions, are being studied with great activity. However, although an impressive variety of elemental compositions have been realized, some combinations of the p-block (semi)metals are lacking in corresponding substructures. The In/Sb combination is extremely rare, and Tl/Sb has not yet been realized at all, although the existence of pseudo-tetrahedral species, for instance, was predicted by quantum chemical studies. Extraction of the novel ternary phase K6InSb3 and of K6Tl2Sb3 with ethane-1,2-diamine (en) yielded binary Zintl anions of these elemental combinations as salts comprising pseudo-tetrahedral anions (InSb3)2- and (TlSb3)2- or nine-vertex cages (In4Sb5)3- and (Tl4Sb5)3-, respectively. To establish efficient synthesis routes, the extractions were monitored using electrospray-ionization mass spectrometry and fractionated crystallization. We thereby isolated salts of two further anions that might represent intermediates on the way to larger species, namely, a novel salt of the Sb73- anion, and a salt of the new binary anion (TlSb7)2-. We describe the experimental approach, the process of its optimization, the geometric structures of the new compounds as well as their electronic structures that were established by DFT calculations.

Ferroelectricity, Piezoelectricity, and Unprecedented Starry Ferroelastic Patterns in Organic-Inorganic (CH3C(NH2)2)3[Sb2X9] (X = Cl/Br/I) Hybrids

In this study, we present a novel class of lead-free hybrid antimony halides incorporating the acetamidinium cation, with the chemical compositions: (CH3C(NH2)2)3[Sb2Cl9] (ACA), (CH3C(NH2)2)3[Sb2Br9] (ABA), and (CH3C(NH2)2)3[Sb2I9] (AIA) . Despite their seemingly analogous chemical formulations, these compounds exhibit diverse physical characteristics, predominantly dictated by the differences in their metal-halide architectures. Indeed, the anionic frameworks of ACA and AIA are reminiscent of well-known ferroelectric materials, with ACA distinguished by its piezoelectric and ferroelastic characteristics, underpinned by a buckled honeycomb two-dimensional (2D) layers of antimony chloride. Conversely, AIA is characterized by its ferroelectric attribute, with discrete bioctahedral units forming a zero-dimensional (0D) structure. A surprising structural deviation constitutes the anionic sublattice of ABA, which amalgamates features from both ACA and AIA, yielding an unprecedented hybrid two-component (0D + 2D) anionic architecture. The ferroelectric properties of AIA have been demonstrated through pyroelectric current measurements and hysteresis loop analyses. Additionally, the noncentrosymmetric nature of ACA and AIA has been corroborated by second harmonic generation experiments. The piezoelectricity of ACA was confirmed using piezoresponse force microscopy (PFM). Furthermore, observations under a polarizing microscope revealed distinct ferroelastic properties in both ACA and ABA, characterized by well-defined and abundant star patterns previously observed only in simple oxides and alloys.

Bis-alkynylphosphine Oxide Pt(II) Complexes: Aggregation-Induced Phosphorescence Enhancement and Mechanochromic Luminescence Properties

Four bis-alkynyl Pt(II) complexes [Pt(dtbpy)(C2-L-P(O)Ph2)2] with dtbpy = 4,4'-ditertbutyl-2,2'-bipyridine and alkynylphosphine oxide ligands (L = no linker, Pt0; phenyl, Pt1; biphenyl, Pt2; naphthyl, Pt3) have been synthesized and fully characterized by spectroscopic methods and single crystal XRD analysis. It has been found that the nature of the π-conjugated linker is a key factor in fine-tuning the emission energy of the complexes in solution and in achieving the aggregation-induced phosphorescence enhancement (AIPE) effect for complex Pt0 with the most compact linker. Phosphine oxide fragment, which can be involved in weak intermolecular interactions, promotes the existence of two solid forms with different luminescence properties. These two forms can be switched from one to another upon grinding, thus featuring distinct mechanochromic luminescence properties. TDDFT calculations are consistent with the experimental results and assign mixed 3MLCT and 3LL'CT solution emission character and 3MMLCT and 3LL'CT emission nature in supramolecular dimeric structures.

How novel is protactinium: Insights into the structure and properties of (PaO)2(SO4)3(H2O)2

Because of the scarcity of protactinium and the challenges associated with its separation and crystallization, even in sulfuric acid media where protactinium is relatively stable, there has been an incomplete understanding of the structural features of protactinium complexes. The characterization of protactinium sulfate complexes has been limited to those in solution, which have left key details unaddressed since the 1960s. This report describes a synthetic strategy to crystallize a protactinium complex using boric acid and sulfuric acid. Herein, the authors detail the results of hydrothermal synthesis and the single-crystal analysis of a novel protactinium sulfate complex, (PaO)2(SO4)3(H2O)2. This work has elucidated structural features, providing groundwork for accurate computational analysis and clarifying previously unknown details on the coordination, denticity, and binding properties of protactinium sulfate complexes.

Magneto-Structural Correlations, Substitution Effects and Slow Relaxation of the Magnetization on Trinuclear Linear Ni(II) Complexes: An Experimental and Theoretical Study

We report the preparation of three neutral linear trinuclear Ni(II) complexes [Ni3(LX)2] (1-3) by self-assembly of Ni(II) ions and N3O3-tripodal Schiff base ligands, LX, which were obtained by condensation between the triamine tris(methylhydrazine)phosphorylsulfide and salicylaldehyde derivatives with substituents X=H (L1) (1), Br (L2) (2) and NO2 (L3) (3) in para position to the phenoxo group. Experimental magneto-structural studies carried out on these complexes indicate that the magnetic exchange interactions between the neighboring Ni(II) ions are ferromagnetic in nature, moderate in magnitude and clearly dependent of the electronic properties of the substituent in para position. Thus, the electron-withdrawing NO2 group decreases the ferromagnetic coupling, whereas the Br substituent, with small electronic effects, does not significantly vary the exchange coupling observed for the unsubstituted complex. Theoretical calculations performed on these complexes, containing ligands with a variety of electron-donating and withdrawing groups in para position to the phenoxo group, support that the ferromagnetic coupling decreases on passing from strong electron-donating to electron-withdrawing groups. Interestingly, complexes 1-3 show weak slow relaxation of the magnetization, with relaxation times (τ) decreasing in the order: 1>2>3. These compounds represent some of the few examples of Ni(II) complexes exhibiting slow magnetic relaxation.

Ph3P-I2-mediated Syntheses of C-12 Carboxamide Indoloquinazolines and 2-Aminosubstituted-indol-3-ones from Isatins and Amines

The Ph3P-I2-mediated reactions between isatins and amines were extensively investigated leading to the discovery of highly selective and divergent routes toward the synthesis of two distinct classes of indole-based frameworks. Through a strategic design of the reaction paths, we overcome potential side reactions to achieve convenient and straightforward one-pot methods to access either indoloquinazolines with C-12 carboxamide or 2-aminosubstituted indol-3-ones using the same reagent system. Mechanistic studies reveal the role of Ph3P-I2 in governing product selectivity, providing an efficient route to novel fused-indolone derivatives with promising applications in drug discovery and medicinal chemistry.

Calcium coordination polymer containing dimethylphosphate ligands and exhibiting nucleating properties towards α and Β crystal polymorphs of isotactic polypropylene

The synthesis, structure and thermal properties of a one-dimensional coordination polymer based on calcium bis(dimethylphosphate) (CaDMP) are reported. The rod-like particles of CaDMP crystallized from water in a monoclinic space group P21/c, and contained Ca[O2P(OCH3)2]2 polymeric chains consisting of the octahedrally coordinated Ca2+ ions bridged by the tridentate dimethylphosphate ligands. The variable temperature powder X-ray diffraction measurements showed that this structure undergoes anisotropic thermal expansion upon heating, with no polymorphic transitions occurring up to 190 °C. Thermolysis of CaDMP began around 260 °C leading to the formation of calcium condensed phosphates and volatile oxophosphorus species. A detailed differential scanning calorimetry (DSC) analysis, combined with a fitting of the experimental data to the Avrami or Liu-Mo kinetic models, revealed that CaDMP accelerates isothermal and non-isothermal crystallization of isotactic polypropylene (iPP). DSC and wide-angle X-ray scattering measurements confirmed the presence of α-iPP and β-iPP crystal domains in the systems loaded with CaDMP particles. The crystallographic analysis indicated that β-iPP polymorph formed via epitaxial crystallization on the surface of CaDMP crystals. Mechanical tests proved that the CaDMP-containing composites exhibited better ductility and impact strength than neat iPP.

Unraveling the Crystal Structures of Picolinic Acid Derivatives: Synthesis, Packing, Interactions, and Conformational Flexibility

Picolinic acid and its derivatives are widely used as pendant arms in ligands for metal ion complexation, with possible biomedical applications, when exploited in the preparation of magnetic resonance imaging contrast agents and radioisotope labeling for α- and β-therapy. Its structural and electronic characteristics make picolinic acid versatile and able to form stable complexes with various metal ions. The present study reports the synthesis of four picolinic acid derivatives useful for both coordination and bioconjugation, featuring a benzyl-protected hydroxy group removable via palladium-catalyzed hydrogenolysis. Chromatography and magnetic resonance assessed the purity, identity, and structural features of the synthesized compounds, ensuring their suitability for the said applications. Single-crystal X-ray diffraction was exploited for structure solution of three of them, revealing that the introduction of specific substituents induces changes in both the molecular structure and the crystal packing, driven by a balance between π-stacking and weak nonbonding contacts. Small changes in the pyridine substituents can induce conformational changes in the opposite benzyl ring orientation, spanning from a planar to a perpendicular orientation. The structural analysis, including Hirshfeld surfaces and energetic frameworks calculations, clarified intermolecular interactions contributing to a better understanding of the solid state behavior of the title compounds.

Crystal structure and Hirshfeld surface analysis of the fungicide metconazole

Metconazole is a systemic triazole fungicide that inhibits the ergosterol bio-synthesis pathway. It is widely used in agriculture to control fungal infections, including rusts, fusarium and septoria diseases. The mol-ecular structure is a three-ring system, namely, 5-(4-chlorobenz-yl)-2,2-dimethyl-1-(1H-1,2,4-triazol-1-ylmeth-yl)cyclo-pentan-1-ol, C17H22ClN3O, consisting of a cyclo-pentan-1-ol with 1,2,4-triazol-1-ylmethyl, gem-dimethyl and 4-chloro-benzyl groups attached at the 1-, 2- and 5-positions of the cyclo-penta-nol ring. It has two stereocentres (cyclo-penta-nol positions 1 and 5) leading to four stereoisomers, with the (1S,5R) form being the most bioactive. Despite its agricultural significance, detailed crystallographic data remain scarce. This study reports the crystal structure and Hirshfeld surface analysis of racemic cis-metconazole [(1S,5R)/(1R,5S)], determined in the monoclinic space group P21/c with two independent mol-ecules in the asymmetric unit (Z' = 2). Both exhibit similar conformations, with minor differences in the cyclo-penta-nol ring puckering and the torsion angles between the three rings. The crystal packing consists of 21-screw-related hy-dro-gen-bonded chains parallel to the b axis, with additional weak C-H⋯N and C-H⋯Cl contacts linking adjacent mol-ecules. Hirshfeld surface analysis indicates that inter-molecular inter-actions are dominated by contacts involving hy-dro-gen (96.1 and 96.7% for the two mol-ecules).