Synthesis, spectroscopic, thermal and antifungal studies on lanthanum(III) and praseodymium(III) derivatives of 1,1-diacetylferrocenyl hydrazones

A series of new coordination complexes of La(III) and Pr(III) with hydrazones, derived from 1,1-diacetylferrocene and different aromatic acid hydrazides have been synthesized and characterized by elemental analyses, electrical conductance, magnetic moment, IR, (1)H NMR, UV-vis spectra and molar conductance. The thermal behaviour of the complexes under non-isothermal condition was investigated by TG and DTG techniques. The antifungal activity of hydrazones and their corresponding complexes were also investigated.     

THE CRYSTAL STRUCTURE OF DIBROMO (PHENYL-2-PYRIDYL DIMETHYLHYDRAZONE)PALLADIUM(II)

Abstract

Nitrogen-containing heterocyclic compounds play an important role in several biological processes. Furthermore, their biological activity seems often to depend upon interaction with a metal ion. Interest in the study of hydrazones and their metal complexes has been growing because of their physiological activity, coordination capability and application in analytical chemistry.^1,2 Many hydrazones and their metallic derivatives show very interesting biological activity, e.g., as antitumour or anticonvulsant agents, and behave as cytotoxic compounds toward tumour cells.³ During the past few years, in addition to platinum compounds, coordination compounds of palladium(II) and (IV) seem to be promising in cancer chemotherapy.⁴ Due to the biological activity of heterocyclic hydrazones and in continuing our systematic investigations of the platinum group metals with hydrazones and generally with heterocyclic nitrogen donor ligands,^5–10 we report here the crystal structure of dibromo(phenyl-2-pyridyldimethylhydrazone) palladium(II).     

Ferrocene substitution in amino acids strengthens the axial binding in Cu(II) complexes and separates the hydrophobic and hydrophilic region in the crystals

This paper reports on the synthesis, characterization and electrochemical properties of four ferrocenylmethyl substituted L-amino acid ligands and their Cu(II) complexes. Structural characterization of the complexes of L-methionine and L-asparagine derived ligands showed axial coordination of weak thioether and amide respectively to Cu(II). Coordination of the thioether group of L-methionine to copper (2.791 A) is shorter than observed in the electron transfer protein plastocyanin (2.9 A). Methionine thioether does not bind in synthetic Cu(II) complexes. The characterization of bis-complexes (metal : ligand ratio 1 : 2) with L-serine and L-threonine derivatives showed axial coordination of water with a shorter Cu-O bond length compared to that observed in the corresponding amino acid complexes. The structures also revealed separation of the hydrophilic and hydrophobic regions due to amino acid and ferrocene respectively which resulted in the formation of interesting H-bonded networks.     

Thermo-Induced Fluorochromism in Two AIE Zinc Complexes: A Deep Insight into the Structure-Property Relationship

Solid-state emitters exhibiting mechano-fluorochromic or thermo-fluorochromic responses represent the foundation of smart tools for novel technological applications. Among fluorochromic (FC) materials, solid-state emissive coordination complexes offer a variety of fluorescence responses related to the dynamic of noncovalent metal-ligand coordination bonds. Relevant FC behaviour can result from the targeted choice of metal cation and ligands. Herein, we report the synthesis and characterization of two different colour emitters consisting of zinc complexes obtained from N,O bidentate ligands with different electron-withdrawing substituents. The two complexes are blue and orange solid-state fluorophores, respectively, highly responsive to thermal and mechanical stress. These emitters show a very different photoluminescent (PL) pattern as recorded before and after the annealing treatment. Through X-ray structural analysis combined with thermal analysis, infrared (IR) spectroscopy, PL, and DFT simulation we provide a comprehensive analysis of the structural feature involved in the fluorochromic response. Notably, we were able to correlate the on-off thermo-fluorochromism of the complexes with the structural rearrangement at the zinc coordination core.     

Synthesis, structure, and properties of the Cu(II) coordination compounds with the pyruvic acid nicotinoyl and isonicotinoyl hydrazones

New coordination compounds of Cu(II) and hydrazones of nicotinic and isonicotinic acids have been prepared. The complexes isolated have been studied by elemental analysis, thermogravimetric analysis, magnetic susceptibility measurements, IR, diffuse reflectance, and EXAFS spectroscopy. The geometry of the compounds has been determined and the type of the ligands coordination has been revealed. Antibacterial activity of the complexes has been studied.     

The coordination chemistry of Zn(II), Cd(II) and Hg(II) complexes with 1,2,4-triazole derivatives

This perspective illustrates the coordination features of complexes constructed by 1,2,4-triazole derivatives and transition metal ions which belong to Group IIB, namely Zn(II), Cd(II) and Hg(II), demonstrates their behaviors in thermal stabilities, gas or liquid adsorption, fluorescence and nonlinear optical properties and also discusses the relation between their properties and crystal structures. Various 1,2,4-triazole derivatives containing versatile donor sites for coordination can be obtained through introducing different substituent groups to C3, N4 and C5 positions, thus offering rich coordination modes. The structures of these complexes rely on their triazole ligands, as well as mixed ligands, metal ions, anions and synthetic conditions. Obviously, the diversity in structure induces the controllability of properties, since the properties are influenced by several factors, which is significant for the applications of potential multifunctional materials.     

Protolitic complexing properties of acylhydrazones of substituted salicylaldehydes and stability constants of their cooper(II) complexes

The acid-base properties of acetyl-and heptoylhydrazones of substituted salicylaldehyde derivatives and the stability of their copper(II) complexes have been studied. For both sets of compounds, the ionization constants of the hydrazones and the stability constants of hydrazone complexes are linear functions of the substituent constants σ. An analogous tendency is found for the antiferromagnetic exchange interaction parameters in dimeric copper(II) nitrate complexes of heptoylhydrazones of substituted salicylaldehyde derivatives. A correlation between the protolytic properties of hydrazones and the magnetic properties of their complexes is suggested.     

Synthesis,spectroscopy and thermal analysis of copper(II) hydrazone complexes

The chelating behavior of some hydrazones towards Cu(II) has been investigated. The isolated complexes were characterized by elemental analysis, magnetic moment, spectra (electronic, IR and ms) and thermal measurements. The IR spectra showed that the ligands are deprotonated in the complexes as bidentate, tridentate and binegative tridentate. Protonation constants of the ligands and the stability constants of their Cu(II) complexes were calculated. Square-planar, square-pyramidal, tetrahedral and/or distorted octahedral structures are proposed. The TGA data help to confirm the chemical formula of the complexes and indicated the steps of their thermal degradations.     

REVIEW: SPECTROSCOPIC STUDIES OF OXOVANADIUM COORDINATION COMPOUNDS

Abstract

In this review we present selected examples of our studies of oxovanadium(IV) and oxovanadium(V) complexes relevant for the bioinorganic chemistry of vanadium. Some of the investigated complexes are good models for different steps of vanadium metabolism or for a better understanding of the structural and electronic peculiarities of the coordination spheres of these oxocations in biomolecules. The investigated systems include ligands such as nucleotides, carbohydrates, phosphates, amino acids, oxine derivatives, porphine-like cores and other simple organic and inorganic ligands. All these complexes have been systematically investigated by means of vibrational (infrared and Raman) and electronic spectroscopy and, in some cases, also by thermal and electrochemical behavior. The potentialities and possibilities of the spectroscopic methodologies are illustrated and discussed and some general trends, useful for the structural characterization of these and similar systems, are emphasized.     

1-Hydrazinophthalazine based hydrazones and their transition metal complexes: Structure and biological activity

Structure, tautomeric rearrangements, acid-base properties and complex formation ability of 1-hydrazinophthalazine hydrazones and their coordination compounds with transition metals are considered. The main factors influencing the structure and physicochemical properties of the complexes, biological activity of phthalazine hydrazones and their complexes are discussed.     

Synthesis and spectral characterization of ternary complexes of oxovanadium(IV) containing some acid hydrazones and 2,2'-bipyridine

An interesting series of heterocyclic base adducts of oxovanadium(IV) complexes have been synthesized by the reaction of vanadium(IV) oxide acetylacetonate with some hydrazones (H(2)L) in the presence of a heterocyclic base 2,2'-bipyridine. The compounds were characterized by analytical and different physico-chemical techniques like IR, electron paramagnetic resonance (EPR) and UV-Vis spectral studies and magnetic studies. The EPR spectra indicate that the free electron is in the d(xy) orbital. The coordination geometry around oxovanadium(IV) in all complexes is octahedral, with one dibasic tridentate ligand L(2-), and one bidentate heterocyclic base. The IR spectra suggest that coordination takes place through azomethine nitrogen and enolate oxygen from the hydrazide moiety and phenolate oxygen. The pyridyl nitrogens of the hydrazones, H(2)L(2) and H(2)L(4) are not involved in the coordination. The molar conductivities show that all the complexes are non-electrolytes. All electronic transitions were assigned. All the compounds are paramagnetic. EPR studies of all compounds suggest axial symmetry. The calculated bonding parameters indicate that in-plane sigma bonding is more covalent than in-plane pi bonding.     

Configurational and constitutional information storage: multiple dynamics in systems based on pyridyl and acyl hydrazones

The C=N group of hydrazones can undergo E/Z isomerization both photochemically and thermally, allowing the generation of a closed process that can be tuned by either of these two physical stimuli. On the other hand, hydrazine-exchange reactions enable a constitutional change in a given hydrazone. The two classes of processes: 1) configurational (physically stimulated) and 2) constitutional (chemically stimulated) give access to short-term and long-term information storage, respectively. Such transformations are reported herein for two hydrazones (bis-pyridyl hydrazone and 2-pyridinecarboxaldehyde phenylhydrazone) that undergo a closed, chemically or physically driven process, and, in addition, can be locked or unlocked at will by metal-ion coordination or removal. These features also extend to acyl hydrazones derived from 2-pyridinecarboxaldehyde. Similarly to the terpydine-like hydrazones, such acyl hydrazones can undergo both constitutional and configurational changes, as well as metal-ion coordination. All these types of hydrazones represent dynamic systems capable of acting as multiple state molecular devices, in which the presence of coordination sites furthermore allows the metal ion-controlled locking and unlocking of the interconversion of the different states.     

Synthesis,characterization and biological applications of new copper(II) complexes of aryl hydrazones

On treatment of copper(II) acetate with aryl hydrazone ligands, four new solid derivatives of copper(II) were produced in appreciable yields. Various characterization techniques including infrared, UV–visible, NMR, electron paramagnetic resonance and mass spectroscopies, elemental analysis, scanning electron microscopy, powder X‐ray diffraction and thermogravimetric analysis revealed a tetra‐coordination in all the mononuclear crystalline complexes with high thermal stability. Further, significant interaction of these novel complexes with calf thymus DNA via intercalative mode of binding was revealed by electronic absorption spectroscopy. The chemical nuclease activity of the complexes on pBR322 DNA was investigated in the presence and absence of oxidizing agent (H₂O₂). A potent nuclease activity was observed only in the presence of H₂O₂. Further, antibacterial and antifungal studies of the new ligands and complexes revealed that the latter possessed comparatively better activity.     

Tetrakis(2-hydroxyphenyl)ethene and derivatives. A structurally preorganized tetradentate ligand system for polymetallic coordination chemistry and catalysis

A topologically unique, conformationally constrained tetradentate ligand system for polymetallic coordination chemistry has been developed: tetrakis(2-hydroxyphenyl)ethene (1a) and substituted derivatives. The design exploits the planarity of the tetraphenylethylene core to impart rigidity to the roughly square oxygen binding array, while maintaining a degree of conformational mobility associated with rotation about the aryl-ethylene carbon-carbon bonds. Tetrakis(2-hydroxyphenyl)ethene derivatives are designed to promote multiple metal bridging over chelating coordination modes. The ligand is synthesized from anisole or 4-tert-butylanisole in four steps via the 2,2'-dimethoxybenzophenone hydrazones 4a,b. The sterically hindered ortho-substituted tetraphenylethylene core is produced in high yield by acid-catalyzed decomposition of the corresponding diaryl diazomethane prepared in situ by oxidation of the hydrazone using nickel peroxide. Deprotection of the methyl ethers using boron tribromide gives tetrakis(2-hydroxyphenyl)ethene (1a), characterized by X-ray crystallography, and tetrakis(5-tert-butyl-2-hydroxyphenyl)ethene (1b). Sterically isolating substituents in the 3-position can be installed via Claisen rearrangement/hydrogenation, providing tetrakis(3-n-propyl-2-hydroxyphenyl)ethene (6) efficiently. To illustrate potential applications of this unprecedented ligand class, two coordination complexes are reported, including tetrakis(2-diethylaluminoxyphenyl)ethene (8), a structurally robust eight-membered-ring aluminum/oxygen crown complex characterized both in solution and in the solid state.     

Synthesis, characterisation and antitubercular activities of a series of pyruvate-containing aroylhydrazones and their Cu-complexes

A series of eight pyruvate-based aroylhydrazones was synthesised and characterised. The reaction of the sodium salts of the aroylhydrazones with one equivalent of copper(II) chloride allowed the isolation of neutral 1:1 complexes in which the hydrazones occupy three basal coordination sites of a square pyramidal Cu(II)-centre, with two solvent molecules completing the coordination sphere. Structural details were obtained through the determination of the crystal structures of two representative pyruvate-based aroylhydrazones and three Cu(II) complexes. The evaluation of the antimycobacterial activity of the sodium salts of the eight pryruvate hydrazones showed that the compounds are essentially inactive in their anionic form. The corresponding neutral Cu(II) complexes, however, exhibit promising antimycobacterial activities if tested under high iron (8 μg Fe per mL) conditions. As observed for the related antimycobacterial agent isoniazid, the activity of the complexes decreases if the M. tuberculosis cells are grown under low iron (0.02 μg Fe per mL) conditions. The Cu(II) complexes may thus have a similar mode of action and may require an iron-containing heme-dependent peroxidase for activation.     

Synthesis, spectral characterization and eukaryotic DNA degradation of thiosemicarbazones and their platinum(IV) complexes

The condensation products of acetophenone (or its derivatives), salicylaldehyde and o-hydroxy-p-methoxybenzophenone with thiosemicarbazide and ethyl- or phenyl-thiosemicarbazide are the investigated thiosemicarbazones. Their reactions with H(2)PtCl(6) produced Pt(IV) complexes characterized by elemental, thermal, mass, IR and electronic spectral studies. The coordination modes were found mononegative bidentate in the acetophenone derivatives and binegative tridentate in the salicylaldehyde derivatives. The complexes were analyzed thermogravimetrically and found highly stable. Some ligands and their complexes were screened against Sarcina sp. and E. coli using the cup-diffusion technique. [Pt(oHAT)(OH)Cl] shows higher activity against E. coli than the other compounds. The degradation power of the tested compounds on the calf thymus DNA supports their selectivity against bacteria and not against the human or related eukaryotic organisms.     

Synthesis,characterization and theoretical investigations of new uranium (VI) and thorium (IV) complexes with 1-furfurylaldehyde-derived Schiff bases as ligands

The present work describes the synthesis and characterization of thorium (IV) and dioxouranium (VI) coordination compounds with three Schiff bases derived from 1-furfurylaldehyde. All coordination compounds were characterized by elemental analysis, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy, and thermal analysis. The structural pattern, the geometry of the complexes and the coordination number of the metal ions were assigned on the basis of physico-chemical parameters, such as FTIR and UV–Vis spectra. The elemental analyses show a 1:1 stoichiometry for thorium coordinative compounds and 1:2 stoichiometry for uranyl ion, respectively. The obtained coordination compounds are stable in air, soluble in some organic solvents (DMF, acetonitrile, DMSO) and show fluorescent properties. The coordination compounds have high molar conductance that indicates their electrolytes nature. On the basis of the obtained experimental results, combined with theoretical studies, the structures of the compounds under study were proposed.     

Mixed Ligand Complexes of 5-arylazo-8-hydroxyquinoline and α-amino Acids with Co(II), Ni(II) and Cu(II)

Ten mixed ligand complexes of the type [M(X-QA)(aa)] and [Ni(X-QA)₂(Haa)(H₂O)],where X-HQA=5-arylazo-8-hydroxyquinoline derivatives, M=Co(II) orCu(II) and Haa=glycine (gly), alanine (ala) or methionine (met), have been prepared. The complexes have been characterized by elemental analysis, IR and electron spectra and thermal analysis. A tetrahedral structure has been proposed for the cobalt(II) and copper(II) complexes with bidentate coordination of amino acids. The nickel(II) complexes have been assigned an octahedral structure with the amino acids acting as monodentate ligands. The thermal behaviour of the complexes has been studied before and after γ-irradiation. This revised version was published online in August 2006 with corrections to the Cover Date.     

四氮唑-1-乙酸及其衍生物金属构筑配合物的研究进展

四氮唑-1-乙酸(Htza)类有机配体具有良好的配位能力和多样的配位形式,在配位化学领域得到了迅速且广泛的研究。本文总结了基于四氮唑-1-乙酸配体构筑的金属配合物的研究进展和这些金属配合物的结构特征,讨论了基于四氮唑-1-乙酸构筑的金属配合物在光学、磁性、催化方面的应用,并对这类配体的发展前景进行了展望。     

Coordination chemistry of buckybowls: from corannulene to a hemifullerene

This work highlights the progress made in coordination chemistry of transition-metal centers to open geodesic polyaromatic hydrocarbons that map onto the surface of C60, the family of compounds known as buckybowls or 'fullerene fragments'. In particular, an overview of our recent gas-phase coordination studies of several bowl-shaped polyarenes toward the dinuclear metal complex, [Rh2(O2CCF3)4], is given. Selected buckybowls include corannulene (C20H10) and two of its derivatives, namely dibenzo[a,g]corannulene (C28H14) and 1,3,5,7,9-penta-tert-butylcorannulene (C40H50), as well as a hemifullerene (C30H12). This study has resulted in the first X-ray structural characterization of buckybowl coordination complexes and has revealed eta2-rim coordination preferences of open geodesic polyarenes in rhodium(ii) binding reactions.