The challenge of cyclic and acyclic schiff bases and related derivatives

A Novel Zn(II) Coordination Polymer: Fluorescence Performances, Molecular Docking and Loaded with Bleomycin-Hydrogels on Hemangiomas

In this study, we successfully synthesized an innovative 1D-Zn(II) coordination polymer, denoted as [Zn(L)(H2O)2]n, employing the Schiff base {4-[(2-hydroxy-3-methoxy-benzylidene)-amino]-benzoic acid} (H2L). The Schiff base was obtained through the reaction of 4-aminobenzoic acid and o-vanillin under slow volatilization conditions. The resulting compound exhibits remarkable green fluorescence emission properties, indicating its potential as a novel fluorescent and sensing material. Hydrogels based on hyaluronic acid (HA) and carboxymethyl chitosan (CMCS), denoted as HA/CMCS hydrogels, were synthesized using a chemical method. Additionally, we utilized bleomycin as a model drug to synthesize a novel bleomycin metal gel and assessed its anti-hemangioma activity. Molecular docking simulations revealed that the Zn complex can form stable bonds with the key target, involving the methoxy and carboxyl groups on the Zn complex.

Structure-directing role of CH⋯X (X = C, N, S, Cl) interactions in three ionic cobalt complexes: X-ray investigation and DFT study using QTAIM Vr predictor to eliminate the effect of pure Coulombic forces

Three cobalt complexes, namely [CoIII(HL1)2(N3)2]ClO4 (1), [CoIII(L2)(HL2)(N3)]ClO4·1.5H2O (2), and [CoIII(L3)(HL3)(NCS)]2 [CoIICl2(NCS)2] (3), where HL1 = 2-(3-(dimethylamino)propyliminomethyl)-6-methoxyphenol, HL2 = 2-(2-(dimethylamino)ethyliminomethyl)-4,6-dichlorophenol, and HL3 = 2-(2-(dimethylamino)ethyliminomethyl)-6-methoxyphenol, as potential tridentate N2O-donor Schiff base ligands, were synthesized and characterized using elemental analysis, IR and UV-vis spectroscopy, and single-crystal X-ray diffraction studies. All three were found to be monomeric ionic complexes. Complex 1 crystallizes in the orthorhombic space group Pbcn, whereas both complexes 2 and 3 crystallize in triclinic space groups, P1̄. Further, 1 and 2 are cationic complexes of octahedral cobalt(iii) with perchlorate anions, whereas complex 3 contains a cationic part of octahedral cobalt(iii) and an anionic part of tetrahedral cobalt(ii). Hydrogen-bonding interactions involving aromatic and aliphatic CH bonds as H-bond donors and the pseudo-halide co-ligands as H-bond acceptors were established, which are important aspects governing the X-ray packing. These interactions were analyzed theoretically using the quantum theory of atoms in molecules (QTAIM) and non-covalent interaction plot (NCI plot) analyses. Moreover, energy decomposition analysis (EDA) was performed to analyze the stabilization of the complexes in terms of the electrostatic, dispersion, and correlation forces.

Dynamic PEG-PLA/Hydroxyurethane Networks Based on Imine Bonds as Reprocessable Elastomeric Biomaterials

The development of dynamic covalent chemistry opens the way to the design of materials able to be reprocessed by an internal exchange reaction under thermal stimulus. Imine exchange differs from other exchange reactions by its relatively low temperature of activation. In this study, amine-functionalized star-shaped PEG-PLA and an aldehyde-functionalized hydroxyurethane modifier were combined to produce PEG-PLA/hydroxyurethane networks incorporating imine bonds. The thermal and mechanical properties of these new materials were evaluated as a function of the initial ratio of amine/aldehyde used during synthesis. Rheological analyses highlighted the dynamic behavior of these vitrimers at moderate temperature (60-85 °C) and provided the flow activation energies. Additionally, the reprocessability of these PEG-PLA/hydroxyurethane vitrimers was assessed by comparing the material properties before reshaping and after three reprocessing cycles (1 ton, 1 h, 70 °C). Hence, these materials can easily be designed to satisfy a specific medical application without properties loss. This work opens the way to the development of a new generation of dynamic materials combining degradable PEG-PLA copolymers and hydroxyurethane modifiers, which could find applications in the shape of medical devices on-demand under mild conditions.

Pharmacological Activities of Schiff Bases and Their Derivatives with Low and High Molecular Phosphonates

This review paper is focused on the design of anthracene and furan-containing Schiff bases and their advanced properties as ligands in complex transition metal ions The paper also provides a brief overview on a variety of biological applications, namely, potent candidates with antibacterial and antifungal activity, antioxidant and chemosensing properties. These advantageous properties are enhanced upon metal complexing. The subject of the review has been extended with a brief discussion on reactivity of Schiff bases with hydrogen phosphonates and the preparation of low and high molecular phosphonates, as well as their application as pharmacological agents. This work will be of interest for scientists seeking new challenges in discovering advanced pharmacological active molecules gaining inspiration from the versatile families of imines and aminophosphonates.

Vanadyl as a Spectroscopic Probe of Tunable Ligand Donor Strength in Bimetallic Complexes

Incorporation of secondary metal ions into heterobimetallic complexes has emerged as an attractive strategy for rational tuning of compounds' properties and reactivity, but direct solution-phase spectroscopic interrogation of tuning effects has received less attention than it deserves. Here, we report the assembly and study of a series of heterobimetallic complexes containing the vanadyl ion, [VO]²⁺, paired with monovalent cations (Cs⁺, Rb⁺, K⁺, Na⁺, and Li⁺) and a divalent cation (Ca²⁺). These complexes, which can be isolated in pure form or generated in situ from a common monometallic vanadyl-containing precursor, enable experimental spectroscopic and electrochemical quantification of the influence of the incorporated cations on the properties of the vanadyl moiety. The data reveal systematic shifts in the V-O stretching frequency, isotropic hyperfine coupling constant for the vanadium center, and V(V)/V(IV) reduction potential in the complexes. These shifts can be interpreted as charge density effects parametrized through the Lewis acidities of the cations, suggesting broad potential for the vanadyl ion to serve as a spectroscopic probe in multimetallic species.

Synthesis and characterization of two piperazine containing macrocycles and their transition metal complexes

Rigidification of the ligand scaffolds has been a particular mechanism of interest employed to achieve properties suitable for MRI contrast, catalysis, or other applications of metal complexes. Towards the goal of targeting a 15-anePyN5Pip type ligand, a serendipitous isolation of a 30-anePy2N10Pip2 aza-macrocycle was achieved, instead. X-ray diffraction and determination of pKa events were carried out and compared to 17-anePyN5Pip. Furthermore, the X-ray diffraction of the Cu(II) and Zn(II) complexes of 17-anePyN5Pip was achieved and compared to previous reports of other first-row transition metal derivatives of this ligand. Determination of the log β with both 30-anePy2N10Pip2 and 17-anePyN5Pip with the divalent MnZn metal-ion series was used to demonstrate the impact that the piperazine ring plays compared to other, less rigid macrocycles reported to date.

Synthesis and Characterization of Zinc(II), Cadmium(II), and Palladium(II) Complexes with the Thiophene-Derived Schiff Base Ligand

Zn(II), Pd(II), and Cd(II) complexes, [L _TH MCl ₂ ] (M = Zn, Pd; X = Br, Cl) and [L _TH Cd(μ-X)X] _n (X = Cl, Br; n = n, 2), supported by the (E)-N ¹,N ¹-dimethyl-N ²-(thiophen-2-ylmethylene)ethane-1,2-diamine (L _TH ) ligand are synthesized and structurally characterized. Density functional theory (DFT) electronic structure calculations and variable-temperature NMR support the presence of two conformers and a dynamic interconversion process of the minor conformer to the major one in solution. It is found that the existence of two relevant complex conformers and their respective ratios in solution depend on the central metal ions and counter ions, either Cl^- or Br^-. Among the two relevant conformers, a single conformer is crystallized and X-ray diffraction analysis revealed a distorted tetrahedral geometry for Zn(II) complexes, and a distorted square planar and square pyramidal geometry for Pd(II) and Cd(II) complexes, respectively. It is shown that [L _TH MCl ₂ ]/LiO ⁱ Pr (M = Zn, Pd) and [L _TH Cd(μ-Cl)Cl] _n /LiO ⁱ Pr can effectively catalyze the ring-opening polymerization (ROP) reaction of rac-lactide (rac-LA) with 94% conversion within 30 s with [L _TH ZnCl ₂ ]/LiO ⁱ Pr at 0 °C. Overall, hetero-enriched poly(lactic acid)s (PLAs) were provided by these catalytic systems with [L _TH ZnCl ₂ ]/LiO ⁱ Pr producing PLA with higher heterotactic bias (P _r up to 0.74 at 0 °C).

Enantiomeric pairs of copper(II) complexes with tridentate Schiff bases derived from R- and S-methionine: the role of decorating organic groups of the ligand in crystal packing and biological activity

Three enantiomeric pairs consisting of copper(II) complexes with tridentate Schiff bases have been synthesized for employing in biological assessments: 1∞[Cu₂(R/S-salmet)₂(H₂O)] (1-R/S·H2O), 1∞[Cu(R/S-3-HOMe-5-Me-salmet)] (2-R/S), and 1∞[Cu(R/S-3-MeO-salmet)] (3-R/S) (where R/S-salmetH₂, R/S-3-HOMe-5-Me-salmetH₂, and R/S-3-MeO-salmetH₂ result from the condensation of R/S-methionine with salicylaldehyde, 2-hydroxy-3-(hydroxymethyl)-5-methylbenzaldehyde, and 3-methoxy-salicylaldehyde, respectively, in a 1 : 1 molar ratio). The crystal structures of 1-R·H2O and 2-R/S are reported. Moreover, the 1-R/S·H2O enantiomers have been subjected to a single-crystal-to-single-crystal (SC-SC) transformation by heating at 160 °C to afford their dehydrated forms, 1∞[Cu₂(R/S-salmet)₂] (1-R/S), whose structures have also been crystallographically determined. The coordination polyhedra of the metal centers, the binding modes of the ligands, and the 1-D double chain assemblies generated by the chiral mononuclear units are comparatively described. The diffuse reflectance UV-Vis and circular dichroism (CD) spectra of compounds 1-R/S·H2O, 1-R/S, and 2-R/S are analysed with respect to their structural peculiarities and compared to those of 3-R/S. The UV-Vis and CD spectra of solutions of 1-R/S, 2-R/S, and 3-R/S point to the collapse of the double chains via dissolution. Biological tests performed on the model eukaryote Saccharomyces cerevisiae indicated low toxicity for 1-R/S, 2-R/S, and 3-R, and moderate toxicity for 3-S. The S-type complexes were accumulated by cells in higher quantity compared to their R-type counterparts due to selective transport via the high-affinity S-methionine transporter, Mup1. A chemogenomic analysis of 3-S toxicity performed on a collection of yeast knockout mutants revealed that most of the deleted genes identified in the screen were involved in the cell response to oxidative stress, calcium-mediated response, or metal homeostasis. Altogether, it was concluded that 3-S accumulation may perturb the redox state of the cell, also interfering with the calcium-mediated response to oxidative stress or metal-related oxidative stress.

Synthesis, Structure, Spectral-Luminescent Properties, and Biological Activity of Chlorine-Substituted N-[2-(Phenyliminomethyl)phenyl]-4-methylbenzenesulfamide and Their Zinc(II) Complexes

New azomethine compounds of 2-(N-tosylamino)benzaldehyde or 5-chloro-2-(N-tosylamino)benzaldehyde and the corresponding chlorine-substituted anilines, zinc(II) complexes based on them have been synthesized. The structures of azomethines and their complexes were determined by elemental analysis, IR, ¹H NMR, X-ray spectroscopy, and X-ray diffraction. It is found that all ZnL₂ complexes have a tetrahedral structure according to XAFS and X-ray diffraction data. The photoluminescent properties of azomethines and zinc complexes in methylene chloride solution and in solid form have been studied. It is shown that the photoluminescence quantum yields of solid samples of the complexes are an order of magnitude higher compared to the solutions and range from 11.34% to 48.3%. The thermal properties of Zn(II) complexes were determined by thermal gravimetric analysis (TGA) and differential scanning calorimetry. The TGA curves of all the compounds suggest their high thermal stability up to temperatures higher than 290 °C. The electrochemical properties of all complexes were investigated by the cyclic voltammetry method. The multilayered devices ITO/PEDOT:PSS/NPD/Zn complex/ TPBI/LiF/Al with wide electroluminescence (EL) color range spanning the range from bluish-green (494 nm) to green (533 nm) and the high values of brightness, current and power efficiency were fabricated. The biological activity of azomethines and zinc complexes has been studied. In the case of complexes, the protistocidal activity of the zinc complex with azomethine of 5-chloro-2-(N-tosylamino)benzaldehyde with 4-chloroaniline was two times higher than the activity of the reference drug toltrazuril.

Synthesis, Characterization and Antibacterial Activities of Ferrocene Ligands and Their Binuclear Complexes

6-Chloro-2-ferrocenyl-1H-benzimidazole and (E)-((4-chloro-2-hydroxyphenylimino)methyl)ferrocene ligands and their Fe(III), Co(II), Cu(II), Zn(II) and Pd(II) complexes were synthesized. The structure of ligands and metal complexes has been investigated by different methods. In addition, magnetic moment, molar conductivity measurements and antibacterial activity of the ligands and the complexes were investigated.

Transition Metal Complexes with Tridentate Schiff Bases (O N O and O N N) Derived from Salicylaldehyde: An Analysis of Their Potential Anticancer Activity

Although it is known that the first case of cancer was recorded in ancient Egypt around 1600 BC, it was not until 1917 during the First World War and the development of mustard gas that chemotherapy against cancer became relevant; however, its properties were not recognised until 1946 to later be used in patients. In this sense, the use of metallopharmaceuticals in cancer therapy was extensively explored until the 1960s with the discovery of cisplatin and its anticancer activity. From that date to the present, the search for more effective, more selective metallodrugs with fewer side effects has been an area of continuous exploration. Efforts have led to considering a wide variety of metals from the periodic table, mainly from the d-block, as well as a wide variety of organic ligands, preferably with proven biological activity. In this sense, various research groups have found an ideal binder in Schiff bases, since their raw materials are easily accessible, their synthesis conditions are friendly and their denticity can be manipulated. Therefore, in this review, we have explored the anticancer and antitumor activity reported in the literature for coordination complexes of d-block metals coordinated with tridentate Schiff bases (O N O and O N N) derived from salicylaldehyde. For this work, we have used the main scientific databases CCDC® and SciFinder®.

Synthesis, characterization, antioxidant and anticancer activities of a new Schiff base and its M(II) complexes derived from 5-fluorouracil

In this study, Schiff base ligand was obtained from the condensation reaction of benzene-1,2-diamine and 5-fluoropyrimidine-2,4(1H,3H)-dione (5-FU). Metal(II) complexes were synthesized with Fe(II), Co(II) and Ni(II) chloride salts. The synthesized ligand and metal complexes were characterized by FT-IR, UV-vis, ¹H-¹³C NMR, elemental analyses, mass spectroscopy, magnetic moments, molar conductivity and thermogravimetric analysis studies. With the help of different techniques reveal Fe(II), Co(II) and Ni(II) complexes have exhibited tetrahedral and octahedral geometry. Ligand acted as bidentate and it binds metal(II) ions through deprotonated-NH, imine-N atom and carbonyl-O atom, respectively. DPPH, ABTS, FRAP, CUPRAC and total antioxidant activity methods were used to determine the antioxidant properties of ligand and metal complexes. According to the results, the synthesized compounds showed very high antioxidant activity compared to 5-FU. The cytotoxicities of the synthesized compounds were performed on MCF-7 (human breast cancer) and L-929 (fibroblast) cell lines using the MTT assay. In addition, the effect of electroporation (EP) on the cytotoxicity of the compounds was investigated. Our results demonstrated that novel Co(II) and Ni(II) complexes show potential as new anticancer agents and ECT may be a viable treatment option for breast cancer.

Adsorption of Pb(II) from water by treatment with an O-hydroxyphenyl thiourea-modified chitosan

An O-hydroxyphenyl thiourea-modified chitosan (OTCS) with excellent Pb(II) adsorption performance and selectivity was prepared as an adsorbent. The structure and morphology of the adsorbent were systematically investigated by SEM, BET, FTIR, EDX, zeta-potential measurements, XPS and XRD. The impacts of the initial Pb(II) concentration, reaction time, temperature, pH value, and coexisting ions were explored. At pH 7 and 303 K, the maximal adsorption capacity of OTCS for Pb(II) was 208.33 mg/g, which was greater than those of other adsorbing materials reported in the literature. The metal ion adsorption kinetics and isotherm models were found to obey pseudo-second-order kinetics and the Langmuir isothermal model, indicating that the adsorption process was monolayer chemisorption. The adsorption process could proceed spontaneously, and the thermodynamic results revealed that the adsorption mechanism was an endothermic reaction. The ion exchange and chelation between the sulfur, nitrogen and oxygen groups on the adsorbent and lead ions endowed the material with excellent adsorption properties. Significantly, OTCS showed excellent selectivity toward Pb(II). Therefore, the adsorbent OTCS is expected to promote the wider application of chitosan in the adsorption of Pb(II).

Synthesis, Characterization, Computational and Biological Activity of Some Schiff Bases and Their Fe, Cu and Zn Complexes

Four new symmetrical Schiff bases derived from 2,2′-diamino-6,6′-dibromo-4,4′-dimethyl-1,1′-biphenyl or 2,2′-diamino-4,4′-dimethyl-1,1′-biphenyl, and 3,5-dichloro- or 5-nitro-salicylaldehyde, were synthesized and reacted with copper-, iron- and zinc-acetate, producing the corresponding complexes. The Schiff bases and their metal complexes were characterized by 1H-, 13C-NMR, IR and UV-Vis spectroscopy and elemental analysis. The structures of one Schiff base and the two zinc complexes were resolved by X-ray structure determination. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level of the latter compounds were carried out to optimize and examine their molecular geometries. The biomedical applications of the Schiff bases and their complexes were investigated as anticancer or antimicrobial agents.

Synthesis of Two Novel Copper (II) Complexes as Potential Inhibitors of HIV-1 Protease Enzyme: Experimental and Theoretical Investigations

In this study, we report the synthesis of two new copper complexes: [Cu(C11H7O2)(SCN)(C10H8N2)], denoted as (C-1), and [Cu(C11H7O2) (C12H8N2) Cl]·H2O, denoted as (C-2). They are based on 2,2′-bipyridine or 1,10-phenanthroline and 2-hydroxy-1-naphtaldehyde ligands. The obtained complexes were characterized by FT-IR, UV-visible spectroscopy, and single-crystal X-ray diffraction analysis. Molecular docking was employed to predict the binding mode involved in the interaction between the two synthetic copper (II) complexes and HIV-1 protease enzyme. The X-ray structural analysis revealed that the crystal structures of both complexes are mainly stabilized by several intra- and intermolecular hydrogen bonds. The fingerprint plots associated with the Hirshfeld surfaces of both complexes clearly show that H···H interactions provide the largest contributions. According to the docking results, the synthesized complexes exhibit promising features which enable them to be bound to the HIV-protease enzyme.

Mixed-Valent Trinuclear CoIII-CoII-CoIII Complex with 1,3-Bis(5-chlorosalicylideneamino)-2-propanol

A mixed-valent trinuclear complex with 1,3-bis(5-chlorosalicylideneamino)-2-propanol (H₃clsalpr) was synthesized, and the crystal structure was determined by the single-crystal X-ray diffraction method at 90 K. The molecule is a trinuclear Co^III-Co^II-Co^III complex with octahedral geometries, having a tetradentate chelate of the Schiff-base ligand, bridging acetate, monodentate acetate coordination to each terminal Co³⁺ ion and four bridging phenoxido-oxygen of two Schiff-base ligands, and two bridging acetate-oxygen atoms for the central Co²⁺ ion. The electronic spectral feature is consistent with the mixed valent Co^III-Co^II-Co^III. Variable-temperature magnetic susceptibility data could be analyzed by consideration of the axial distortion of the central Co²⁺ ion with the parameters Δ = –254 cm⁻¹, λ = –58 cm⁻¹, κ = 0.93, tip = 0.00436 cm³ mol⁻¹, θ = –0.469 K, g_z = 6.90, and g_x = 2.64, in accordance with a large anisotropy. The cyclic voltammogram showed an irreversible reduction wave at approximately −1.2 V·vs. Fc/Fc⁺, assignable to the reduction of the terminal Co³⁺ ions.

Multinuclear Ni(II) and Cu(II) complexes of a meso 6 + 6 macrocyclic amine derived from trans-1,2-diaminocyclopentane and 2,6-diformylpyridine

Four hexanuclear chloride and sulphate Ni(II) and Cu(II) complexes 1, 2, 4 and 5 and one tetranuclear nitrate Cu(II) complex 3 have been synthesised from appropriate metal salts and 6 + 6 octadecaaza macrocyclic ligands. All obtained coordination compounds have been characterised by elemental analysis, spectroscopic methods (ESI MS, NMR and EPR), magnetic susceptibility measurements and X-ray crystallography. Their X-ray crystal structures reveal different coordination modes of metal cations involved in the obtained centro-symmetrical coordination compounds. The conformational folding of the macrocyclic ligand adopted in the respective complexes depends on the number of metal cations bound within the macrocycle but not on their type. The cavities of these multinuclear complexes might be occupied by solvent molecules and counter anions bound by hydrogen bonds or might be empty in the case where the macrocyclic ring of the ligand is squeezed in the middle. All obtained Ni(II) and Cu(II) coordination compounds are paramagnetic. This has been proved by their ¹H NMR and EPR spectra and magnetic measurements. Direct current (DC) variable-temperature magnetic susceptibility measurements on the polycrystalline samples of 1-5 were carried out in the temperature range of 1.8-300 K. The magnetic behaviour of 1 and 2 is dominated by the magnetic anisotropy of the nickel(II) ion masking the magnetic interactions between magnetic centres. The magnetic data of 3-5 reveal small antiferromagnetic interactions within the Cu₄ and Cu₆ units. EPR experiments for 3-5 show, at 9.6 and 34 GHz frequencies, that the predominant contribution to the orbitals occupied by the unpaired electrons in the ground state originates from d_x²-y².

Controlling chirality in the synthesis of 4 + 4 diastereomeric amine macrocycles derived from trans-1,2-diaminocyclopentane and 2,6-diformylpyridine

A few suitably long dialdehyde and primary diamine building blocks of a predetermined chirality have been designed and synthesized to enable controlled and efficient synthesis of all six possible diastereomers of 4 + 4 macrocyclic amine derived from trans-1,2-diaminocyclopentane (DACP) and 2,6-diformypyridine (DFP) units. Although two out of six diastereomers have been reported recently, their synthesis presented here is more direct and occurs with an improved yield. This family of 4 + 4 macrocycles contains one pair of homochiral enantiomers of identical RRRRRRRR and SSSSSSSS configurations of DACP units, two different meso forms (meso I of alternating RRSSRRSS and meso II of neighboring RRRRSSSS configuration of DACP moieties) as well as one pair of heterochiral enantiomers, where configuration of one diamine fragment is opposite to the other three diamine parts, RRRRRRSS and SSSSSSRR, respectively. The structures of each type of macrocycle in solid state have been confirmed by single crystal analyses of a macrocyclic amine in its suitable protonated form. The different symmetry of each type of macrocycle in solutions has been proved by ¹H and ¹³C NMR spectra of their hydrochloride derivatives. The chiral nature of two different pairs of optically active enantiomers has been established by circular dichroism spectra. These chiral 4 + 4 diastereomeric macrocycles are receptors for chiral guests and recognize in solution 10-camphorsulfonic acid as well as chiral tartaric acid.

Excited state dynamics of Zn-salophen complexes

Zn-salophen complexes are a promising class of fluorescent chemosensors for nucleotides and nucleic acids. We have investigated, by means of steady state UV-Vis, ultrafast transient absorption, fluorescence emission and time dependent density functional theory (TD-DFT) the behavior of the excited states of a salicylidene tetradentate Schiff base (Sal), its Zn(II) coordination compound (Zn-Sal) and the effect of the interaction between Zn-Sal and adenosine diphosphate (ADP). TD-DFT shows that the deactivation of the excited state of Sal occurs through torsional motion, due to its rotatable bonds and twistable angles. Complexation with Zn(II) causes rigidity so that the geometry changes in the excited states with respect to the ground state structure are minimal. By addition of ADP to a freshly prepared Zn-Sal ethanol solution, a longer relaxation constant, in comparison to Zn-Sal, was measured, indicative of the interaction between Zn-Sal and ADP. After a few days, the Zn-Sal-ADP solution displayed the same static and dynamic behavior of a solution containing only the Sal ligand, demonstrating that the coordination of the ADP anion to Zn(II)leads to the demetallation of the Sal ligand. Fluorescence measurements also revealed an enhanced fluorescence at 375 nm following the addition of ADP to the solution, caused by the presence of 2,3-diamino naphthalene that is formed by demetallation and partial decomposition of the Sal ligand. The efficient fluorescence of this species at 375 nm could be selectively detected and used as a probe for the detection of ADP in solution.

Large interaction energy for the homodimer and the heterodimer extracted from the supramolecular chain of a bent trinuclear zinc(ii) complex with a reduced Schiff base ligand

The coordinated amino groups in a trinuclear zinc complex participate in strong H-bonding interactions that have been analysed. The dimerization energy is very large for both the homodimer and the heterodimer in the 1D supramolecular chain.

Highly red-emissive salen–indium complexes: impact of 4-amino-substitution on the photophysical properties

4-NR2-appended salen–indium complexes were prepared via a one-pot synthetic pathway. The complexes exhibited narrow-bandwidth red emissions with high photoluminescence quantum yields that are the highest among the reported salen-based luminophores.

Ferrocene functionalized enantiomerically pure Schiff bases and their Zn(ii) and Pd(ii) complexes: a spectroscopic, crystallographic, electrochemical and computational investigation

A combination of X-ray diffraction, IR, UV-vis and NMR spectroscopy together with computational methods was used to characterize and study the properties of the title compounds.

Copper in tumors and the use of copper-based compounds in cancer treatment

Copper homeostasis is strictly regulated by protein transporters and chaperones, to allow its correct distribution and avoid uncontrolled redox reactions. Several studies address copper as involved in cancer development and spreading (epithelial to mesenchymal transition, angiogenesis). However, being endogenous and displaying a tremendous potential to generate free radicals, copper is a perfect candidate, once opportunely complexed, to be used as a drug in cancer therapy with low adverse effects. Copper ions can be modulated by the organic counterpart, after complexed to their metalcore, either in redox potential or geometry and consequently reactivity. During the last four decades, many copper complexes were studied regarding their reactivity toward cancer cells, and many of them could be a drug choice for phase II and III in cancer therapy. Also, there is promising evidence of using ⁶⁴Cu in nanoparticles as radiopharmaceuticals for both positron emission tomography (PET) imaging and treatment of hypoxic tumors. However, few compounds have gone beyond testing in animal models, and none of them got the status of a drug for cancer chemotherapy. The main challenge is their solubility in physiological buffers and their different and non-predictable mechanism of action. Moreover, it is difficult to rationalize a structure-based activity for drug design and delivery. In this review, we describe the role of copper in cancer, the effects of copper-complexes on tumor cell death mechanisms, and point to the new copper complexes applicable as drugs, suggesting that they may represent at least one component of a multi-action combination in cancer therapy.

Contemporary macrocycles for discrete polymetallic complexes: precise control over structure and function

The growth of multimetallic clusters and complexes can proceed in the presence of suitable ligands, but often leads to polydisperse structures with poor solubility. As an alternative approach, macrocyclic molecules can anchor the multimetallic complex, directing its formation and stabilizing the resulting product. This approach can provide excellent control over the growth of clusters, and offers a handle to control solubility and other properties of the resulting complexes. In this Tutorial Review, we discuss recent activity (primarily the last two decades) directed at the controlled and reproducible synthesis of multimetallic complexes using macrocyclic ligands. Throughout the review, we focus on the unusual structures that are only accessible by using macrocycles as ligands, and their unique properties.