Chemistry of molecular and supramolecular structures of vanadium(IV) and dioxygen-bridged V(V) complexes incorporating tridentate hydrazone ligands

Simultaneous formation of non-oxidovanadium(iv) and oxidovanadium(v) complexes incorporating phenol-based hydrazone ligands in aerobic conditions

A family of non-oxidovanadium(iv) complexes incorporating multidentate hydrazone ligands were synthesized through a thermodynamically unfavourable process along with oxidovanadium(v) species.

Multiple adaptation of constitutional dynamic networks and information storage in constitutional distributions of acylhydrazones

We report a study of the behavior of four dynamic covalent libraries (DCLs) based on acylhydrazones aAbB and of the corresponding square constitutional dynamic networks (CDNs) NA-ND under the effect of three agents, namely, metal cations, base + metal cations and light irradiation; in particular, the successful switching of the CDN NB between two orthogonal distributions results, respectively, from metallo-selection and photo-selection. The four DCLs undergo triple adaptation when subjected to the three agents with the generation of specific CDN distributions characteristic of each of the four DCLs. The ternary outputs displayed by the DCLs present three states (-1, 0 and 1) related to three different constitutional distributions expressed in response to the triple inputs applied. This latter process amounts to the storage of molecular information in dynamic distributions rather than in selective interactions between complementary entities undergoing molecular recognition.

Exploring the effect of hydroxylic and non-hydroxylic solvents on the reaction of [VIVO(β-diketonate)2] with 2-aminobenzoylhydrazide in aerobic and anaerobic conditions

Refluxing [V^IVO(β-diketonate)₂], namely [V^IVO(acetylacetonate)₂] and [V^IVO(benzoylacetonate)₂], separately with an equivalent or excess amount of 2-aminobenzoylhydrazide (ah) in laboratory grade (LG) CH₃OH in aerobic conditions afforded non-oxidovanadium(iv) and oxidovanadium(v) complexes of the type [V^IV(L¹)₂] (1), [V^VO(L¹)(OCH₃)]₂ (3) and [V^IV(L²)₂] (2), and [V^VO(L²)(OCH₃)] (4), respectively. (L¹)^2- and (L²)^2- represent the dianionic forms of 2-aminobenzoylhydrazone of acetylacetone (H₂L¹) and benzoylacetone (H₂L²), respectively, (general abbreviation, H₂L), which was formed by the in situ condensation of ah with the respective coordinated [β-diketonate] in medium-to-good yield. The yield of different resulting products was dependent upon the ratio of ah to [V^IVO(β-diketonate)₂]. For example, the yield of 1 and 2 complexes increased significantly associated with a decrease in the amount of 3 and 4 with an increase in the molar ratio of ah. Upon replacing CH₃OH by a non-hydroxylic solvent, LG CHCl₃, the above reaction yielded only oxidovanadium(v) complexes of the type [V^VO(L¹)(OH)]₂ (5), [V^VO(L²)(OH)] (6) and [VO₃(L)₂] (7, 8) whereas, upon replacing CHCl₃ by another non-hydroxylic solvent, namely LG CH₃CN, only the respective [VO₃(L)₂] (7, 8) complex was isolated in 72-78% yield. However, upon performing the above reactions in the absence of air using dry CH₃OH or dry CHCl₃, only the respective [V^IV(L)₂] complex was obtained, suggesting that aerial oxygen was the oxidising agent and the type of pentavalent product formed was dependent upon the nature of solvent used. Complexes 3 and 4 were converted, respectively, to 7 and 8 on refluxing in LG CHCl₃via the respective unstable complex 5 and 6. The DFT calculated change in internal energy (ΔE) for the reactions 2[V^VO(L²)(OCH₃)] + 2H₂O → 2[V^VO(L²)(OH)] + 2CH₃OH and 2[V^VO(L²)(OH)] → [VO₃(L²)₂] + H₂O was, respectively, +3.61 and -7.42 kcal mol^-1, suggesting that the [V^VO(L²)(OH)] species was unstable and readily transformed to the stable [VO₃(L²)₂] complex. Upon one-electron reduction at an appropriate potential, each of 7 and 8 generated mixed-valence [(L)V^VO-(μ-O)-OV^IV(L)]^- species, which showed valence-delocalisation at room temperature and localisation at 77 K. Some of the complexes showed a wide range of toxicity in a dose-dependent manner against lung cancer cells comparable with that observed with cis-platin.

Synthesis, characterization, X-ray crystal structure, DFT calculation, DNA binding, and antimicrobial assays of two new mixed-ligand copper(II) complexes

Two new Cu(II) complexes, [Cu(L)(phen)] (1), [Cu(L)(bipy)] (2), where L(2-)=(3-methoxy-2oxidobenzylidene)benzohydrazidato, phen=1,10 phenanthroline, and bipy=2,2' bipyridine, were prepared and fully characterized using elemental analyses, FT-IR, molar conductivity, and electronic spectra. The structures of both complexes were also determined by X-ray diffraction. It was found that, both complexes possessed square pyramidal coordination environment in which, Cu(II) ions were coordinated by donor atoms of HL and two nitrogens of heterocyclic bases. Computational studies were performed using DFT calculations at B3LYP/6-311+G(d,p) level of theory. DNA binding activities of these complexes were also investigated using electronic absorption, competitive fluorescence titration and cyclic voltammetry studies. The obtained results indicated that binding of the complexes to DNA was of intercalative mode. Furthermore, antimicrobial activities of these compounds were screened against microorganisms.

N'-[(E)-2-Hy-droxy-5-meth-oxy-benzyl-idene]pyridine-4-carbohydrazide monohydrate

The title compound, C₁₄H₁₃N₃O₃·H₂O, adopts an E conformation with respect to the azomethine bond and crystallizes in the amide form. An intra­molecular O—H⋯N hydrogen bond occurs. In the crystal, the lattice water molecule plays a major role in the supramolecular architecture by interconnecting adjacent molecules into a three-dimensional netwrok by means of O—H⋯O, O—H⋯N and N—H⋯O hydrogen-bonding inter­actions. The structure also features two non-classical C—H⋯O inter­actions.

N'-[(E)-(3-Fluoro-pyridin-2-yl)methyl-idene]benzohydrazide monohydrate

The title compound, C₁₃H₁₀FN₃O·H₂O, exists in the E conformation with respect to the azomethane C=N double bond. The mol­ecule is close to planar with a maximum deviation of 0.286 (2) Å. The pyridine ring is essentially coplanar with the central C(= O)N₂C unit [dihedral angle = 2.02 (3)°] and the phenyl ring exhibits a dihedral angle of 14.41 (10)° with respect to the central unit. The crystal structure features O—H⋯N, N—H⋯O and O—H⋯O hydrogen-bond inter­actions between the solvent water and the benzohydrazide mol­ecules, as well as C—H⋯O hydrogen bonds and C—F⋯π [3.0833 (18) Å] inter­actions.

2-Nitro-N′-[1-(pyridin-2-yl)ethylidene]benzohydrazide

In the title compound, C₁₄H₁₂N₄O₃, the dihedral angle between the benzene ring and the pyridine ring is 60.9 (2)°. The major twist in the mol­ecule occurs about the (NH)—(CO)—C_ar—C_ar (ar = aromatic) bond, the relevant torsion angle being 63.97 (12)°. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R₂²(8) loops.

Evaluation of DNA binding, DNA cleavage, protein binding and in vitro cytotoxic activities of bivalent transition metal hydrazone complexes

Divalent Co, Ni and Cu hydrazone complexes containing [N'-(phenyl(pyridine-2-yl)methylidene) benzohydrazide] ligand were synthesised and characterised. Interactions of these complexes with DNA revealed an intercalative mode of binding between them. Further, all the hydrazone chelates showed moderate ability to cleave pUC19 DNA. Synchronous fluorescence spectra proved that the interaction of metal complexes with bovine serum albumin (BSA) resulted in a conformational change of the latter. Assay on the cytotoxicity of the above complexes against HeLa tumor cells and NIH 3T3 normal cells revealed that the complexes are toxic only against tumor cells but not to normal cells. In all the biological assays, the complex with copper ion as the metal center showed enhanced activities than the other two.

Versatile binding properties of a di-2-pyridyl ketone nicotinoylhydrazone ligand: crystal structure of a Cu(II) complex

Six new copper complexes of di-2-pyridyl ketone nicotinoylhydrazone (HDKN) have been synthesized. The complexes have been characterized by a variety of spectroscopic techniques and the structure of [Cu(DKN)(2)]·H(2)O has been determined by single crystal X-ray diffraction. The compound [Cu(DKN)(2)]·H(2)O crystallized in the monoclinic space group P2(1) and has a distorted octahedral geometry. The IR spectra revealed the presence of variable modes of chelation for the investigated ligand. The EPR spectra of compounds [Cu(2)(DKN)(2)(μ-N(3))(2)] and [Cu(2)(DKN)(2)(μ-NCS)(2)] in polycrystalline state suggest a dimeric structure as they exhibited a half field signal, which indicate the presence of a weak interaction between two Cu(II) ions in these complexes.

Design and characterization of Cu(II) complexes from 2-benzoylpyridine benzhydrazone: crystallographic evidence for coordination versatility

The syntheses and characterization of six copper(II) complexes of 2-benzoylpyridine benzhydrazone in the form of [Cu(BPB)(2)], [Cu(BPB)Cl].H(2)O, [Cu(BPB)Br], [Cu(2)(BPB)(2)](ClO(4))(2).4H(2)O, [Cu(BPB)N(3)].H(2)O, and [Cu(BPB)NCS].H(2)O.CH(3)OH are reported. The analytical methods used for the characterization of complexes include partial elemental analyses, IR, electronic and EPR spectra, conductivity measurements, magnetic susceptibility measurements and single crystal X-ray diffraction. From the crystal structure, it is clear that the hydrazone adopts the E conformation about the azo bond to attach to the metal through the N(py)-N(azo)-O chelating system. In the EPR spectra of complexes in DMF at 77K four hyperfine quartets in the parallel region could be resolved and a half field signal is observed at 1500 G for complex [Cu(2)(BPB)(2)](ClO(4))(2).4H(2)O in polycrystalline state at 298 K which gives evidence for its binuclear nature indicating a weak interaction between the two Cu(II) ions.