Supramolecular Nature of Multicomponent Crystals Formed from 2,2'-Thiodiacetic Acid with 2,6-Diaminopurine or N9-(2-Hydroxyethyl)adenine

The synthesis and characterization of the multicomponent crystals formed by 2,2'-thiodiacetic acid (H2tda) and 2,6-diaminopurine (Hdap) or N9-(2-hydroxyethyl)adenine (9heade) are detailed in this report. These crystals exist in a salt rather than a co-crystal form, as confirmed by single crystal X-ray diffractometry, which reflects their ionic nature. This analysis confirmed proton transfer from the 2,2'-thiodiacetic acid to the basic groups of the coformers. The new multicomponent crystals have molecular formulas [(H9heade+)(Htda-)] 1 and [(H2dap+)2(tda2-)]·2H2O 2. These were also characterized using FTIR, 1H and 13C NMR and mass spectroscopies, elemental analysis, and thermogravimetric/differential scanning calorimetry (TG/DSC) analyses. In the crystal packing the ions interact with each other via O-H⋯N, O-H⋯O, N-H⋯O, and N-H⋯N hydrogen bonds, generating cyclic hydrogen-bonded motifs with graph-set notation of R22(16), R22(10), R32(10), R33(10), R22(9), R32(8), and R42(8), to form different supramolecular homo- and hetero-synthons. In addition, in the crystal packing of 2, pairs of diaminopurinium ions display a strong anti-parallel π,π-stacking interaction, characterized by short inter-centroids and interplanar distances (3.39 and 3.24 Å, respectively) and a fairly tight angle (17.5°). These assemblies were further analyzed energetically using DFT calculations, MEP surface analysis, and QTAIM characterization.

H(N3)dap (Hdap = 2,6-Diaminopurine) Recognition by Cu2(EGTA): Structure, Physical Properties, and Density Functional Theory Calculations of [Cu4(μ-EGTA)2(μ-H(N3)dap)2(H2O)2]·7H2O

Reactions in water between the Cu2(µ-EGTA) chelate (EGTA = ethylene-bis(oxyethyleneimino)tetraacetate(4-) ion) and Hdap in molar ratios 1:1 and 1:2 yield only blue crystals of the ternary compound [Cu4(μ-EGTA)2(μ-H(N3)dap)2(H2O)2]·7H2O (1), which has been studied via single-crystal X-ray diffraction and various physical methods (thermal stability, spectral and magnetic properties), as well as DFT theoretical calculations. In the crystal, uncoordinated water is disordered. The tetranuclear complex molecule also has some irrelevant disorder in an EGTA-ethylene moiety. In the complex molecule, both bridging organic molecules act as binucleating ligands. There are two distorted five- and two six-coordinated Cu(II) centers. Each half of EGTA acts as a tripodal tetradentate Cu(II) chelator, with a mer-NO2 + O(ether, distal) conformation. Hdap exhibits the tautomer H(N3)dap, with the dissociable H-atom on its less basic N-heterocyclic atom. These features favor the efficient cooperation between Cu-N7 or Cu-N9 bonds with appropriate O-EGTA atoms, as N6-H···O or N3-H···O interligand interactions, respectively. The bridging role of both organics determines the tetranuclear dimensionality of the complex. In this crystal, such molecules associate in zig-zag chains built by alternating π-π interactions between the five- or six-atom rings of Hdap ligands of adjacent molecules. DFT theoretical calculations (using two different theoretical models and characterized by the quantum theory of "atoms in molecules") reveal the importance of these π-π interactions between Hdap ligands, as well as those corresponding to the referred hydrogen bonds in the contributed tetranuclear molecule.

The Copper(II)-Thiodiacetate (tda) Chelate as Efficient Receptor of N9-(2-Hydroxyethyl)Adenine (9heade): Synthesis, Molecular and Crystal Structures, Physical Properties and DFT Calculations of [Cu(tda)(9heade)(H2O)]·2H2O

Considering that Cu(tda) chelate (tda: dithioacetate) is a receptor for adenine and related 6-aminopurines, this study reports on the synthesis, molecular and crystal structures, thermal stability, spectral properties and DFT calculations related to [Cu(tda)(9heade)(H2O)]·2H2O (1) [9heade: N9-(2-hydroxyethyl)adenine]. Concerning the molecular recognition of (metal chelate)-(adenine synthetic nucleoside), 1 represents an unprecedented metal binding pattern (MBP) for 9heade. However, unprecedentedly, the Cu(tda)-9heade molecular recognition in 1 is essentially featured in the Cu-N1(9heade) bond, without any N6-H⋯O(carboxyl tda) interligand interaction. Nevertheless, N1 being the most basic donor for N9-substituted adenines, this Cu-N1 bond is now assisted by an O2-water-mediated interaction (N6-H⋯O2 and O2⋯Cu weak contact). Also, in the crystal packing, the O-H(ol) of 9heade interacts with its own adenine moiety as a result of an O3-water-mediated interaction (O(ol)-H⋯O3 plus O3-H36⋯π(adenine moiety)). Both water-mediated interactions seem to be responsible for serious alterations in the physical properties of crystalline or grounded samples. Density functional theory calculations were used to evaluate the interactions energetically. Moreover, the quantum theory of atoms-in-molecules (QTAIM), in combination with the noncovalent interaction plot (NCIPlot), was used to analyze the interactions and rationalize the existence and relative importance of hydrogen bonding, chalcogen bonding and π-stacking interactions. The novelty of this work resides in the discovery of a novel binding mode for N9-(2-hydroxyethyl)adenine. Moreover, the investigation of the important role of water in the solid state of 1 is also relevant, along with the chalcogen bonding interactions demonstrated by the density functional theory (DFT) study.

Catalytic activation of remote alkenes through silyl-rhodium(III) complexes

The tandem isomerization-hydrosilylation reaction is a highly valuable process able to transform mixtures of internal olefins into linear silanes. Unsaturated and cationic hydrido-silyl-Rh(III) complexes have proven to be effective catalysts for this reaction. Herein, three silicon-based bidentate ligands, 8-(dimethylsilyl)quinoline (L1), 8-(dimethylsilyl)-2-methylquinoline (L2) and 4-(dimethylsilyl)-9-phenylacridine (L3), have been used to synthesize three neutral [RhCl(H)(L)PPh₃] (1-L1, 1-L2 and 1-L3) and three cationic [Rh(H)(L)(PPh₃)₂][BAr^F₄] (2-L1, 2-L2 and 2-L3) Rh(III) complexes. Among the neutral compounds, 1-L2 could be characterized in the solid state by X-ray diffraction showing a distorted trigonal bipyramidal structure. Neutral complexes (1-L1, 1-L2 and 1-L3) failed to catalyze the hydrosilylation of olefins. On the other hand, the cationic compound 2-L2 was also characterized by X-ray diffraction showing a square pyramidal structure. The unsaturated and cationic Rh(III) complexes 2-L1, 2-L2 and 2-L3 showed significant catalytic activity in the hydrosilylation of remote alkenes, with the most sterically hindered (2-L2) being the most active one.

Design, Synthesis, and Structure-Activity Relationship Studies of New Quinone Derivatives as Antibacterial Agents

Resistance to antibacterial agents is a growing global public health problem that reduces the efficacy of available antibacterial agents, leading to increased patient mortality and morbidity. Unfortunately, only 16 antibacterial drugs have been approved by the FDA in the last 10 years, so it is necessary to develop new agents with novel chemical structures and/or mechanisms of action. In response to this, our group takes up the challenge of designing a new family of pyrimidoisoquinolinquinones displaying antimicrobial activities against multidrug-resistant Gram-positive bacteria. Accordingly, the objective of this study was to establish the necessary structural requirements to obtain compounds with high antibacterial activity, along with the parameters controlling antibacterial activity. To achieve this goal, we designed a family of compounds using different strategies for drug design. Forty structural candidates were synthesized and characterized, and antibacterial assays were carried out against high-priority bacterial pathogens. A variety of structural properties were modified, such as hydrophobicity and chain length of functional groups attached to specific carbon positions of the quinone core. All the synthesized compounds inhibited Gram-positive pathogens in concentrations ranging from 0.5 to 64 µg/mL. Two derivatives exhibited minimum inhibitory concentrations of 64 µg/mL against Klebsiella pneumoniae, while compound 28 demonstrated higher potency against MRSA than vancomycin.

Rational Coformer Selection in the Development of 6-Propyl-2-thiouracil Pharmaceutical Cocrystals

Pharmaceutical multicomponent solids have proved to efficiently modulate the physicochemical properties of active pharmaceutical ingredients. In this context, polyphenols are interesting coformers for designing pharmaceutical cocrystals due to their wide safety profile and interesting antioxidant properties. The novel 6-propyl-2-thiouracil multicomponent solids have been obtained by mechanochemical synthesis and fully characterized by powder and single-crystal X-ray diffraction methods. The analysis of supramolecular synthons has been further performed with computational methods, with both results revealing a robust supramolecular organization influenced by the different positions of the hydroxyl groups within the polyphenolic coformers. All novel 6-propyl-2-thiouracil cocrystals show an enhanced solubility profile, but unfortunately, their thermodynamic stability in aqueous media is limited to 24 h.

Metformin-NSAIDs Molecular Salts: A Path towards Enhanced Oral Bioavailability and Stability

According to the World Health Organization, more than 422 million people worldwide have diabetes. The most common oral treatment for type 2 diabetes is the drug metformin (MTF), which is usually formulated as a hydrochloride to achieve higher water solubility. However, this drug is also highly hygroscopic, thus showing stability problems. Another kind of worldwide prescribed drug is the non-steroidal anti-inflammatory drug (NSAID). These latter, on the contrary, show a low solubility profile; therefore, they must be administered at high doses, which increases the probability of secondary effects. In this work, novel drug-drug pharmaceutical solids combining MTF-NSAIDs have been synthesized in solution or by mechanochemical methods. The aim of this concomitant treatment is to improve the physicochemical properties of the parent active pharmaceutical ingredients. After a careful solid-state characterization along with solubility and stability studies, it can be concluded that the new molecular salt formulations enhance not only the stability of MTF but also the solubility of NSAIDs, thus giving promising results regarding the development of these novel pharmaceutical multicomponent solids.

Lithium anthraquinoids as catalysts in the ROP of lactide and caprolactone into cyclic polymers

New lithium anthraquinoids 2b–d active in the synthesis of cyclic PLA and cyclic PCL have been synthesized and fully characterized.

Easy Handling and Cost-Efficient Processing of a Tb3+-MOF: The Emissive Capacity of the Membrane-Immobilized Material, Water Vapour Adsorption and Proton Conductivity

The development of convenient, non-complicated, and cost-efficient processing techniques for packing low-density MOF powders for industry implementation is essential nowadays. To increase MOFs' availability in industrial settings, we propose the synthesis of a novel 3D Tb-MOF (1) and a simple and non-expensive method for its immobilization in the form of pellets and membranes in polymethacrylate (PMMA) and polysulphone (PSF). The photoluminescent properties of the processed materials were investigated. To simulate industrial conditions, stability towards temperature and humidity have been explored in the pelletized material. Water-adsorption studies have been carried out in bulk and processed materials, and because of the considerable capacity to adsorb water, proton-conduction studies have been investigated for 1.

Metal-Organic Frameworks Based on a Janus-Head Biquinoline Ligand as Catalysts in the Transformation of Carbonyl Compounds into Cyanohydrins and Alcohols

A new family of metal-organic frameworks (MOFs) named GR-MOFs with the chemical formula {[M _x (BCA) _y ](H₂O) _z (DMF) _w } (x,y,z,w: 1,1,2,0; 1,1.5,0,1; 1,2,2,1; and 1,1,0,2 for GR-MOF-11 to 14, respectively) based on s-block [M: Sr (GR-MOF-11), Ba (GR-MOF-14)] and d-block [M: Y (GR-MOF-12) and Cd (GR-MOF-13)] metals together with the biquinoline ligand 2,2'-bicinchoninic acid (H₂BCA) has been synthetized by a solvothermal route and fully characterized by elemental and thermogravimetric analysis, Fourier transform infrared spectroscopy, photoluminescence, particle size distribution through optical microscopy, electrophoretic mobility, and finally, X-ray single-crystal and powder diffraction. The structural characterization reveals that these 2D and 3D MOFs possess a rich variety of coordination modes that maintained the Janus-head topology on the ligand in most of the cases. The new MOFs were studied in the catalyzed cyanosilylation and hydroboration of an extensive group of aldehydes and ketones, wherein the s-block metal-based MOFs GR-MOF-11 and GR-MOF-14 provided the highest efficiency ever reported in the MOF-catalyzed cyanosilylation of carbonyl compounds by using only 0.5 mol % of catalyst loading, room temperature, and solvent-free conditions. Furthermore, the hydroboration of ketones has been reported for the first time with this type of s-block metal catalysts obtaining from moderate to good conversions.

Antibacterial Activity of Two Zn-MOFs Containing a Tricarboxylate Linker

Metal-organic frameworks (MOFs) can be used as reservoirs of metal ions with relevant antibacterial effects. Here, two novel Zn-based MOFs with the formulas [Zn₄(μ₄-O)(μ-FA)L₂] (GR-MOF-8) and [Zn₄(μ₄-O)L₂(H₂O)] (GR-MOF-9) (H₃L: 5-((4-carboxyphenyl)ethynyl) in isophthalic acid and FA (formate anion) were solvothermally synthetized and fully characterized. The antibacterial activity of GR-MOF-8 and 9 was investigated against Staphylococcus aureus (SA) and Escherichia Coli (EC) by the agar diffusion method. Both bacteria are among the most relevant human and animal pathogens, causing a wide variety of infections, and are often related with the development of antimicrobial resistances. While both Zn-based materials exhibited antibacterial activity against both strains, GR-MOF-8 showed the highest inhibitory action, likely due to a more progressive Zn release under the tested experimental conditions. This is particularly evidenced in the inhibition of SA, with an increasing effect of GR-MOF-8 with time, which is of great significance to ensure the disappearance of the microorganism.

Lanthanide(III) Ions and 5-Methylisophthalate Ligand Based Coordination Polymers: An Insight into Their Photoluminescence Emission and Chemosensing for Nitroaromatic Molecules

The work presented herein reports on the synthesis, structural and physico-chemical characterization, luminescence properties and luminescent sensing activity of a family of isostructural coordination polymers (CPs) with the general formula [Ln₂(μ₄-5Meip)₃(DMF)]_n (where Ln(III) = Sm (1_Sm), Eu (2_Eu), Gd (3_Gd), Tb (4_Tb) and Yb (5_Yb) and 5Meip = 5-methylisophthalate, DMF = N,N-dimethylmethanamide). Crystal structures consist of 3D frameworks tailored by the linkage between infinite lanthanide(III)-carboxylate rods by means of the tetradentate 5Meip ligands. Photoluminescence measurements in solid state at variable temperatures reveal the best-in-class properties based on the capacity of the 5Meip ligand to provide efficient energy transfers to the lanthanide(III) ions, which brings intense emissions in both the visible and near-infrared (NIR) regions. On the one hand, compound 5_Yb displays characteristic lanthanide-centered bands in the NIR with sizeable intensity even at room temperature. Among the compounds emitting in the visible region, 4_Tb presents a high QY of 63%, which may be explained according to computational calculations. At last, taking advantage of the good performance as well as high chemical and optical stability of 4_Tb in water and methanol, its sensing capacity to detect 2,4,6-trinitrophenol (TNP) among other nitroaromatic-like explosives has been explored, obtaining high detection capacity (with K_sv around 10⁵ M^-1), low limit of detection (in the 10^-6-10^-7 M) and selectivity among other molecules (especially in methanol).

Drug-Inclusive Inorganic–Organic Hybrid Systems for the Controlled Release of the Osteoporosis Drug Zoledronate

Bisphosphonates (BPs) are common pharmaceutical treatments used for calcium- and bone-related disorders, the principal one being osteoporosis. Their antiresorptive action is related to their high affinity for hydroxyapatite, the main inorganic substituent of bone. On the other hand, the phosphonate groups on their backbone make them excellent ligands for metal ions. The combination of these properties finds potential application in the utilization of such systems as controlled drug release systems (CRSs). In this work, the third generation BP drug zoledronate (ZOL) was combined with alkaline earth metal ions (e.g., Sr²⁺ and Ba²⁺) in an effort to synthesize new materials. These metal–ZOL compounds can operate as CRSs when exposed to appropriate experimental conditions, such as the low pH of the human stomach, thus releasing the active drug ZOL. CRS networks containing Sr²⁺ or Ba² and ZOL were physicochemically and structurally characterized and were evaluated for their ability to release the free ZOL drug during an acid-driven hydrolysis process. Various release and kinetic parameters were determined, such as initial rates and release plateau values. Based on the drug release results of this study, there was an attempt to correlate the ZOL release efficiency with the structural features of these CRSs.

Multifunctional Lanthanide-Based Metal-Organic Frameworks Derived from 3-Amino-4-hydroxybenzoate: Single-Molecule Magnet Behavior, Luminescent Properties for Thermometry, and CO2 Adsorptive Capacity

Herein, we describe and study a new family of isostructural multifunctional metal–organic frameworks (MOFs) with the formula {[Ln₅L₆(OH)₃(DMF)₃]·5H₂O}_n (where (H₂L) is 3-amino-4-hydroxybenzoic acid ligand) for magnetism and photoluminescence. Interestingly, three of the materials (Dy-, Er-, and Yb-based MOFs) present single-molecule magnet (SMM) behavior derived from the magnetic anisotropy of the lanthanide ions as a consequence of the adequate electronic distribution of the coordination environment. Additionally, photoluminescence properties of the ligand in combination with Eu and Tb counterparts were studied, including the heterometallic Eu–Tb mixed MOF that shows potential as ratiometric luminescent thermometers. Finally, the porous nature of the framework allowed showing the CO₂ sorption capacity.

A new family of isostructural multifunctional metal−organic frameworks has been described and studied for magnetism and photoluminescence. Interestingly, some materials present single-molecule magnet behavior, and photoluminescence properties of the ligand in combination with Eu and Tb counterparts were studied, including the heterometallic Eu−Tb mixed MOF that shows potential as ratiometric luminescent thermometers. Finally, the porous nature of the framework allowed showing the CO₂ sorption capacity.

Combined experimental and theoretical investigation on the magnetic properties derived from the coordination of 6-methyl-2-oxonicotinate to 3d-metal ions

Five new compounds are reported herein starting from 2-hydroxy-6-methylnicotinic acid (H2h6mnic) and first-row transition metal ions, although H2h6mnic shows a prototropy in solution to lead to the 6-methyl-2-oxonicotinate (6m2onic) ligand that is the molecule eventually present in the compounds. The structural and chemical characterization reveals the following chemical formulae: {[MnNa(μ₃-6m2onic)₂(μ-6m2onic)(MeOH)]·H₂O·MeOH}_n (1Mn), {[M₂Na₂(μ₃-6m2onic)₂(μ-6m2onic)₂(μ-H₂O)(H₂O)₆](NO₃)₂}_n [M^II = Co (2Co) and Ni (3Ni)], 2[Cu₂(6m2onic)₃(μ-6m2onic)(MeOH)]·[Cu₂(6m2onic)₂(μ-6m2onic)₂]·2[Cu(6m2onic)₂(MeOH)]·32H₂O (4Cu) and {[Cu(μ-6m2onic)₂]·6H₂O}_n (5Cu) (where 6m2onic = 6-methyl-2-oxonicotinate). An unusual structural diversity is observed for the compounds, ranging from isolated complexes (in 4Cu), 1D arrays (in 1Mn and 5Cu) and 3D frameworks (in 2Co and 3Ni). Magnetic properties have been studied for all compounds. Analysis of the magnetic dc susceptibility and magnetization data for 4Cu and 5Cu suggests the occurrence of ferromagnetic exchange, which is well explained by broken-symmetry and CASSCF calculations. The sizeable easy-plane magnetic anisotropy present in compound 2Co allows for a field-induced magnet behaviour with an experimental effective energy barrier of 16.2 cm^-1, although the slow relaxation seems to be best described through Raman and direct processes in agreement with the results of ab initio calculations.

Water soluble organometallic small molecules as promising antibacterial agents: synthesis, physical-chemical properties and biological evaluation to tackle bacterial infections

The Na[3,3'-Fe(8-I-1,2-C₂B₉H₁₀)₂] and Na[2,2'-M(1,7-C₂B₉H₁₁)] (M = Co³⁺, Fe³⁺) small molecules are synthesized and the X-ray structures of [(H₃O)(H₂O)₅][2,2'-Co(1,7-C₂B₉H₁₁)₂] and [Cs(MeCN)][8,8'-I₂-Fe(1,2 C₂B₉H₁₀)₂], both displaying a transoid conformation of the [M(C₂B₉)₂]^- framework, are reported. Importantly, the supramolecular structure of [(H₃O)(H₂O)₅][2,2'-Co(1,7-C₂B₉H₁₁)₂] presents 2D layers leading to a lamellar arrangement of the anions while the cation layers form polymeric water rings made of six- and four-membered rings of water molecules connected via OH⋯H hydrogen bonds; B-H⋯O contacts connect the cationic and anionic layers. Herein, we highlight the influence of the ligand isomers (ortho-/meta-), the metal effect (Co³⁺/Fe³⁺) on the same isomer, as well as the influence of the presence of the iodine atoms on the physical-chemical and biological properties of these molecules as antimicrobial agents to tackle antibiotic-resistant bacteria, which were tested with four Gram-positive bacteria, five Gram-negative bacteria, and three Candida albicans strains that have been responsible for human infections. We have demonstrated an antimicrobial effect against Candida species (MIC of 2 and 3 nM for Na[3,3'-Co(8-I-1,2-C₂B₉H₁₀)₂] and Na[2,2'-Co(1,7-C₂B₉H₁₁)₂], respectively), and against Gram-positive and Gram-negative bacteria, including multiresistant MRSA strains (MIC of 6 nM for Na[3,3'-Co(8-I-1,2-C₂B₉H₁₀)₂]). The selectivity index for antimicrobial activity of Na[3,3'-Co(1,2-C₂B₉H₁₁)₂] and Na[3,3'-Co(8-I-1,2-C₂B₉H₁₀)₂] compounds is very high (165 and 1180, respectively), which reveals that these small anionic metallacarborane molecules may be useful to tackle antibiotic-resistant bacteria. Moreover, we have demonstrated that the outer membrane of Gram-negative bacteria constitutes an impermeable barrier for the majority of these compounds. Nonetheless, the addition of two iodine groups in the structure of the parent Na[3,3'-Co(1,2-C₂B₉H₁₁)₂] had an improved effect (3-7 times) against Gram-negative bacteria. Possibly the changes in their physical-chemical properties make the meta-isomers and the ortho-di-iodinated small molecules more permeable for crossing this barrier. It should be emphasized that the most active metallabis(dicarbollide) small molecules are both transoid conformers in contrast to the ortho- [3,3'-Co(1,2-C₂B₉H₁₁)₂]^- that is cisoid. The fact that these small molecules cross the mammalian membrane and have antimicrobial properties but low toxicity for mammalian cells (high selectivity index, SI) represents a promising tool to treat infectious intracellular bacteria. Since there is an urgent need for antibiotic discovery and development, this study represents a relevant advance in the field.

catena-Poly[oxidanium [tris{μ-[amino(iminio)methyl]phosphonato}zincate(II)]]

The crystal structure of the anionic zinc–[amino(iminio)methyl]phosphonate one-dimensional coordination polymer, Zn-AIMP, is reported; the negative charge is balanced by an oxidanium cation (H3O+) to give the composition {(H3O)[Zn(CH4N2PO3)3]} n . The building unit of the coordination polymer comprises a divalent Zn2+ cation (site symmetry \overline3..) and three [amino(iminio)methyl]phosphonate mono-anionic ligands (point group symmetry m). The AIMP ligand exists in a zwitterionic form with a total charge −1 as the phosphonate is fully deprotonated (–PO3 2−), while the amino(iminio)methyl moiety is protonated (H2N—C—NH2 +).

Exploiting the Multifunctionality of M2+/Imidazole-Etidronates for Proton Conductivity (Zn2+) and Electrocatalysis (Co2+, Ni2+) toward the HER, OER, and ORR

This work deals with the synthesis and characterization of one-dimensional (1D) imidazole-containing etidronates, [M₂(ETID)(Im)₃]·nH₂O (M = Co²⁺ and Ni²⁺; n = 0, 1, 3) and [Zn₂(ETID)₂(H₂O)₂](Im)₂, as well as the corresponding Co²⁺/Ni²⁺ solid solutions, to evaluate their properties as multipurpose materials for energy conversion processes. Depending on the water content, metal ions in the isostructural Co²⁺ and Ni²⁺ derivatives are octahedrally coordinated (n = 3) or consist of octahedral together with dimeric trigonal bipyramidal (n = 1) or square pyramidal (n = 0) environments. The imidazole molecule acts as a ligand (Co²⁺, Ni²⁺ derivatives) or charge-compensating protonated species (Zn²⁺ derivative). For the latter, the proton conductivity is determined to be ∼6 × 10^-4 S·cm^-1 at 80 °C and 95% relative humidity (RH). By pyrolyzing in 5%H₂-Ar at 700-850 °C, core-shell electrocatalysts consisting of Co²⁺-, Ni²⁺-phosphides or Co²⁺/Ni²⁺-phosphide solid solution particles embedded in a N-doped carbon graphitic matrix are obtained, which exhibit improved catalytic performances compared to the non-N-doped carbon materials. Co²⁺ phosphides consist of CoP and Co₂P in variable proportions according to the used precursor and pyrolytic conditions. However, the Ni²⁺ phosphide is composed of Ni₂P exclusively at high temperatures. Exploration of the electrochemical activity of these metal phosphides toward the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) reveals that the anhydrous Co₂(ETID)(Im)₃ pyrolyzed at 800 °C (CoP/Co₂P = 80/20 wt %) is the most active trifunctional electrocatalyst, with good integrated capabilities as an anode for overall water splitting (cell voltage of 1.61 V) and potential application in Zn-air batteries. This solid also displays a moderate activity for the HER with an overpotential of 156 mV and a Tafel slope of 79.7 mV·dec^-1 in 0.5 M H₂SO₄. Ni²⁺- and Co²⁺/Ni²⁺-phosphide solid solutions show lower electrochemical performances, which are correlated with the formation of less active crystalline phases.

5-Phenyl-3-(2-phosphonoethyl)-1,2,3-triazol-1-ium chloride

This new triazole-functionalized phospho­nic acid, PTEPHCl, was synthesized by the ‘click’ reaction of the alkyl azide diethyl-(2-azido­eth­yl)phospho­nate with phenyl­acetyl­ene to give the dieth­yl[2-(4-phenyl-1H-1,2,3-triazol-1-yl)eth­yl]phospho­nate ester, which was then hydrolyzed under acidic conditions (HCl) to give the ‘free’ phospho­nic acid. The use of HCl for the hydrolysis caused protonation of the triazole ring, rendering the compound cationic, charged-balanced by a Cl⁻ anion.

The new triazole-functionalized phospho­nic acid 5-phenyl-3-(2-phosphono­eth­yl)-1,2,3-triazol-1-ium chloride, C₁₀H₁₃N₃O₃P⁺·Cl⁻ (PTEPHCl), was synthesized by the ‘click’ reaction of the alkyl azide diethyl-(2-azido­eth­yl)phospho­nate with phenyl­acetyl­ene to give the dieth­yl[2-(4-phenyl-1H-1,2,3-triazol-1-yl)eth­yl]phospho­nate ester, which was then hydrolyzed under acidic conditions (HCl) to give the ‘free’ phospho­nic acid. The use of HCl for the hydrolysis caused protonation of the triazole ring, rendering the compound cationic, charged-balanced by a Cl⁻ anion. There are extensive hydrogen-bonding inter­actions in the structure of PTEPHCl, involving the phospho­nic acid (–PO₃H₂) group, the triazolium ring and the Cl⁻ anion.

Tris(2-Pyridylmethylamine)V(O)2 Complexes as Counter Ions of Diprotonated Decavanadate Anion: Potential Antineoplastic Activity

The synthesis and theoretical-experimental characterization of a novel diprotanated decavanadate is presented here due to our search for novel anticancer metallodrugs. Tris(2-pyridylmethyl)amine (TPMA), which is also known to have anticancer activity in osteosarcoma cell lines, was introduced as a possible cationic species that could act as a counterpart for the decavanadate anion. However, the isolated compound contains the previously reported vanadium (V) dioxido-tpma moieties, and the decavanadate anion appears to be diprotonated. The structural characterization of the compound was performed by infrared spectroscopy and single-crystal X-ray diffraction. In addition, DFT calculations were used to analyze the reactive sites involved in the donor-acceptor interactions from the molecular electrostatic potential maps. The level of theory mPW1PW91/6–31G(d)-LANL2DZ and ECP = LANL2DZ for the V atom was used. These insights about the compounds’ main interactions were supported by analyzing the noncovalent interactions utilizing the AIM and Hirshfeld surfaces approach. Molecular docking studies with small RNA fragments were used to assess the hypothesis that decavanadate’s anticancer activity could be attributed to its interaction with lncRNA molecules. Thus, a combination of three potentially beneficial components could be evaluated in various cancer cell lines.

A gliclazide complex based on palladium towards Alzheimer's disease: promising protective activity against Aβ-induced toxicity in C. elegans

A new palladium coordination compound based on gliclazide with the chemical formula [Pd(glz)₂] (where glz = gliclazide) has been synthesized and characterised. The structural characterization reveals that this material consists of mononuclear units formed by a Pd²⁺ ion coordinated to two molecules of the glz ligand, in which palladium ions exhibit a distorted plane-square coordination sphere. This novel material behaves like a good and selective inhibitor of butyrylcholinesterase, one of the most relevant therapeutic targets against Alzheimer's disease. Analysis of the enzyme kinetics showed a mixed mode of inhibition, the title compound being capable of interacting with both the free enzyme and the enzyme-substrate complex. Finally, the palladium compound shows promising protective activity against Aβ-induced toxicity in the Caenorhabditis elegans model, which has never been reported.

Catalytic Performance and Electrophoretic Behavior of an Yttrium-Organic Framework Based on a Tricarboxylic Asymmetric Alkyne

A new Y-based metal-organic framework (MOF) GR-MOF-6 with a chemical formula of {[YL(DMF)₂]·(DMF)}_n {H₃L = 5-[(4-carboxyphenyl)ethynyl] isophthalic acid; DMF = N,N-dimethylformamide} has been prepared by a solvothermal route. Structural characterization reveals that this novel material is a three-dimensional MOF in which the coordination of the tritopic ligand to Y(III) metal ions leads to an intercrossing channel system extending over three dimensions. This material has proven to be a very efficient catalyst in the cyanosilylation of carbonyls, ranking second in catalytic activity among the reported rare earth metal-based MOFs described so far but with the lowest required catalyst loading. In addition, its electrophoretic behavior has been studied in depth, providing a zero-charge point between pH 4 and 5, a peak electrophoretic mobility of -1.553 μm cm V^-1 s^-1, and a ζ potential of -19.8 mV at pH 10.

Role of hydrazone substituents in determining the nuclearity and antibacterial activity of Zn(II) complexes with pyrazolone-based hydrazones

Hydrazones and their metal derivatives are very important compounds in medicinal chemistry due to their reported variety of biological activities, such as antibacterial, antifungal and anticancer action. Five hydrazone-pyrazolone ligands...

Rational design of carborane-based Cu2-paddle wheel coordination polymers for increased hydrolytic stability

A new unsymmetric carborane-based dicarboxylic linker provided a 1D Cu₂-paddle wheel coordination polymer (2) with much higher hydrolytic stability than the corresponding 2D Cu₂-paddle wheel polymer (1), obtained from a related more symmetrical carborane-based linker. Both 1 and 2 were used as efficient heterogeneous catalysts for a model aza-Michael reaction but only 2 can be reused several times without significant degradation in catalytic activity.

Novel Polymorphic Cocrystals of the Non-Steroidal Anti-Inflammatory Drug Niflumic Acid: Expanding the Pharmaceutical Landscape

Any time the pharmaceutical industry develops a new drug, potential polymorphic events must be thoroughly described, because in a crystalline pharmaceutical solid, different arrangements of the same active pharmaceutical ingredient can yield to very different physicochemical properties that might be crucial for its efficacy, such as dissolution, solubility, or stability. Polymorphism in cocrystal formulation cannot be neglected, either. In this work, two different cocrystal polymorphs of the non-steroidal anti-inflammatory drug niflumic acid and caffeine are reported. They have been synthesized by mechanochemical methods and thoroughly characterized in solid-state by powder and single crystal X-ray diffraction respectively, as well as other techniques such as thermal analyses, infrared spectroscopy and computational methods. Both theoretical and experimental results are in agreement, confirming a conformational polymorphism. The polymorph NIF-CAF Form I exhibits improved solubility and dissolution rate compared to NIF-CAF Form II, although Form II is significantly more stable than Form I. The conditions needed to obtain these polymorphs and their transition have been carefully characterized, revealing an intricate system.

Broadening the scope of high structural dimensionality nanomaterials using pyridine-based curcuminoids

We present a new heteroditopic ligand (3pyCCMoid) that contains the typical skeleton of a curcuminoid (CCMoid) decorated with two 3-pyridyl groups. The coordination of 3pyCCMoid with ZnII centres results in a set of novel coordination polymers (CPs) that display different architectures and dimensionalities (from 1D to 3D). Our work analyses how synthetic methods and slight changes in the reaction conditions affect the formation of the final materials. Great efforts have been devoted toward understanding the coordination entities that provide high dimensional systems, with emphasis on the characterization of 2D materials, including analyses of different types of substrates, stability and exfoliation in water. Here, we foresee the great use of CCMoids in the field of CPs and emphasize 3pyCCMoid as a new-born linker.

Phase Transformation Dynamics in Sulfate-Loaded Lanthanide Triphosphonates. Proton Conductivity and Application as Fillers in PEMFCs

Phase transformation dynamics and proton conduction properties are reported for cationic layer-featured coordination polymers derived from the combination of lanthanide ions (Ln3+) with nitrilo-tris(methylenephosphonic acid) (H6NMP) in the presence of sulfate ions. Two families of materials are isolated and structurally characterized, i.e., [Ln2(H4NMP)2(H2O)4](HSO4)2·nH2O (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Er, Yb; n = 4-5, Series I) and [Ln(H5NMP)]SO4·2H2O (Ln = Pr, Nd, Eu, Gd, Tb; Series II). Eu/Tb bimetallic solid solutions are also prepared for photoluminescence studies. Members of families I and II display high proton conductivity (10-3 and 10-2 S·cm-1 at 80 °C and 95% relative humidity) and are studied as fillers for Nafion-based composite membranes in PEMFCs, under operating conditions. Composite membranes exhibit higher power and current densities than the pristine Nafion membrane working in the range of 70-90 °C and 100% relative humidity and with similar proton conductivity.

Structural and biological characterization of anticancer nickel(II) bis(benzimidazole) complex

In the present study, nickel(II) complex with 2-[2-[2-(1H-benzimidazol-2-yl)ethylsulfanyl]ethyl]-1H-benzimidazole (tebb) of formula [Ni(tebb)₂](ClO₄)₂ has been prepared and its structure was proved by X-ray crystallography. The central nickel atom is in deformed octahedral vicinity. Four nitrogen atoms of two ligands form plane of octahedral and sulfur atoms are in apical positions. Perchlorate anions are outside the coordination sphere. The coordination compound was tested for its biological activities in an array of in vitro assays. It was found that the synthesized complex possesses interesting biological activity, which is most likely related to its cell-type related uptake kinetics. The synthesized complex is readily uptaken by malignant MDA-MB-231 and CACO-2 cells with the lowest uptake by healthy Hs27 fibroblasts. The lowest IC₅₀ values were obtained for MDA-MB-231 cells (5.2-12.7 μM), highlighting exceptional differential cytotoxicity (IC₅₀ values for healthy fibroblasts were 38.6-51.5 μM). Furthermore, it was found the complex is capable to cause hydrolytic DNA cleavage, promotes an efficient DNA fragmentation and to trigger an extensive formation of intracellular reactive oxygen species. Overall, current work presents a synthesis of Ni(II) coordination compound with interesting biological behavior and with a promising potential to be further tested in pre-clinical models.

Crystallization, Luminescence and Cytocompatibility of Hexagonal Calcium Doped Terbium Phosphate Hydrate Nanoparticles

Luminescent lanthanide-containing biocompatible nanosystems represent promising candidates as nanoplatforms for bioimaging applications. Herein, citrate-functionalized calcium-doped terbium phosphate hydrate nanophosphors of the rhabdophane type were prepared at different synthesis times and different Ca2+/Tb3+ ratios by a bioinspired crystallization method consisting of thermal decomplexing of Ca2+/Tb3+/citrate/phosphate/carbonate solutions. Nanoparticles were characterized by XRD, TEM, SEM, HR-TEM, FTIR, Raman, Thermogravimetry, inductively coupled plasma spectroscopy, thermoanalysis, dynamic light scattering, electrophoretic mobility, and fluorescence spectroscopy. They displayed ill-defined isometric morphologies with sizes ≤50 nm, hydration number n ~ 0.9, tailored Ca2+ content (0.42-8.11 wt%), and long luminescent lifetimes (800-2600 µs). Their relative luminescence intensities in solid state are neither affected by Ca2+, citrate content, nor by maturation time for Ca2+ doping concentration in solution below 0.07 M Ca2+. Only at this doping concentration does the maturation time strongly affect this property, decreasing it. In aqueous suspensions, neither pH nor ionic strength nor temperature affect their luminescence properties. All the nanoparticles displayed high cytocompatibility on two human carcinoma cell lines and cell viability correlated positively with the amount of doping Ca2+. Thus, these nanocrystals represent promising new luminescent nanoprobes for potential biomedical applications and, if coupled with targeting and therapeutic moieties, they could be effective tools for theranostics.

Anti-cancer and anti-inflammatory activities of a new family of coordination compounds based on divalent transition metal ions and indazole-3-carboxylic acid

A new family of mononuclear coordination compounds has been synthetized and characterized: [M(3-ind)₂(H₂O)₂] (M = Co (1), Ni (2), Zn (3), Fe (4), Mn (5); 3-ind = indazole-3-carboxylate). These materials are mononuclear coordination compounds that possess strong hydrogen bond interactions. The anti-inflammatory effects of these compounds were assayed in lipopolysaccharide activated RAW 264.7 macrophages by inhibition of NO production. Moreover, the cytotoxicity of the complexes and the ligand in RAW 264.7 cells were determined for the first time. The most significant results were obtained for the compounds 4 and 5 reaching values of NO inhibition close to 80% at 48 h, and above to 90% at 72 h of treatment. The highest inhibitory effects on NO production were showed at the range 7-23 μg/mL for compounds 4 and 5. As a consequence, compounds 4 and 5 could be potential drugs due to the interesting anti-inflammatory properties showed. The anti-cancer potential of these compounds has been also tested against different tumor cell lines. The cytotoxicity of the ligand and of compounds 2 and 3 were assayed in three cell lines: HT29, colon cancer cells, Hep-G2, hepatoma cells and B16-F10 melanoma cells. The best results have been achieved with compound 2 in HepG2 and B16-F10 cell lines, being between 1.5 and 2 times more effective that the ligand in HepG2 cells, and B16-F10 cells. All in all, indazole-3-carboxylic acid is a promising ligand for the formation of coordination compounds with biochemical properties.

Two Isostructural URJC-4 Materials: From Hydrogen Physisorption to Heterogeneous Reductive Amination through Hydrogen Molecule Activation at Low Pressure

Herein, two novel isostructural metal-organic frameworks (MOFs) M-URJC-4 (M = Co, Ni; URJC = "Universidad Rey Juan Carlos") with open metal sites, permanent microposity, and large surface areas and pore volumes have been developed. These novel MOFs, with polyhedral morphology, crystallize in the monoclinic P2₁/c space group, exhibiting a three-dimensional structure with microporous channels along the c axis. Initially, they were fully characterized and tested in hydrogen (H₂) adsorption at different conditions of temperature and pressure. The physisorption capacities of both materials surpassed the gravimetric H₂ uptake shown by most MOF materials under the same conditions. On the basis of the outstanding adsorption properties, the Ni-URJC-4 material was used as a catalyst in a one-pot reductive amination reaction using various carbonyl compounds and primary amines. A possible chemical pathway to obtain secondary amines was proposed via imine formation, and remarkable performances were accomplished. This work evidences the dual ability of M-URJC-4 materials to be used as a H₂ adsorbent and a catalyst in reductive amination reactions, activating molecular H₂ at low pressures for the reduction of C═N double bonds and providing reference structural features for the design of new versatile heterogeneous materials for industrial application.

Rational design of an unusual 2D-MOF based on Cu(i) and 4-hydroxypyrimidine-5-carbonitrile as linker with conductive capabilities: a theoretical approach based on high-pressure XRD

Herein, we present, for the first time, a 2D-MOF based on copper and 4-hydroxypyrimidine-5-carbonitrile as the linker. Each MOF layer is perfectly flat and neutral, as is the case for graphene. High pressure X-ray diffraction measurements reveal that this layered structure can be modulated between 3.01 to 2.78 Å interlayer separation, with an evident piezochromism and varying conductive properties. An analysis of the band structure indicates that this material is conductive along different directions depending on the application of pressure or H doping. These results pave the way for the development of novel layered materials with tunable and efficient properties for pressure-based sensors.

Strasseriolides A-D, A Family of Antiplasmodial Macrolides Isolated from the Fungus Strasseria geniculata CF-247251

A novel family of four potent antimalarial macrolides, strasseriolides A-D (1-4), has been isolated from cultures of Strasseria geniculata CF-247251, a fungal strain obtained from plant tissues. The structures of these compounds, including their absolute configurations, were elucidated by HRMS, NMR spectroscopy, and X-ray single-crystal diffraction. The four compounds gave respective IC₅₀ values of 9.810, 0.013, 0.123, and 0.128 μM against Plasmodium falciparum 3D7 parasites with no significant cytotoxicity against the HepG2 cell line.

5-Aminopyridine-2-carboxylic acid as appropriate ligand for constructing coordination polymers with luminescence, slow magnetic relaxation and anti-cancer properties

Five new coordination polymers (CPs) constructed of aminopyridine-2-carboxylate (ampy) ligand have been synthesized and fully characterized. Three of them correspond to metal-organic chains built from the coordination of ampy to sodium and lanthanides with formulae [MNa(ampy)₄]_n (M = terbium (2), erbium (1) and ytterbium (3)) resembling a previously reported dysprosium material which shows anticancer activity. On another level, the reaction of Hampy with cobalt and copper ions ({[CoK(ampy)₃(H₂O)₃](H₂O)₃}_n (4) and [Cu(ampy)₂]_n (5)) lead to CPs with variable dimensionalities, which gives the opportunity of analyzing the structural properties of this new family. Lanthanide materials display solid state intense photoluminescent emissions in both the visible and near-infrared region and exhibit slow relaxation of magnetization with frequency dependence of the out-of-phase susceptibility. More interestingly, in our search for multifunctional materials, we have carried out antitumor measurements of these compounds. These multidisciplinary studies of metal complexes open up the possibility for further exploring the applications in the fields of metal-based drugs.

Designing Single-Molecule Magnets as Drugs with Dual Anti-Inflammatory and Anti-Diabetic Effects

We have designed and synthesized two novel cobalt coordination compounds using bumetanide (bum) and indomethacin (ind) therapeutic agents. The anti-inflammatory effects of cobalt metal complexes with ind and bum were assayed in lipopolysaccharide stimulated RAW 264.7 macrophages by inhibition of nitric oxide production. Firstly, we determined the cytotoxicity and the anti-inflammatory potential of the cobalt compounds and ind and bum ligands in RAW 264.7 cells. Indomethacin-based metal complex was able to inhibit the NO production up to 35% in a concentration-dependent manner without showing cytotoxicity, showing around 6–37 times more effective than indomethacin. Cell cycle analysis showed that the inhibition of NO production was accompanied by a reversion of the differentiation processes in LPS-stimulated RAW 264.7 cells, due to a decreased of cell percentage in G0/G1 phase, with the corresponding increase in the number of cells in S phase. These two materials have mononuclear structures and show slow relaxation of magnetization. Moreover, both compounds show anti-diabetic activity with low in vitro cell toxicities. The formation of metal complexes with bioactive ligands is a new and promising strategy to find new compounds with high and enhanced biochemical properties and promises to be a field of great interest.