Formylferrocenyl-3-hydroxyl-2-naphthoylhydrazone and its transition metal complexes

Summary Formylferrocenyl-3-hydroxyl-2-naphthoylhydrazone and its transition metal coordination compounds have been synthesized and characterized by elemental analyses, i.r., ¹H-n.m.r., u.v.-vis., t.g.-d.t.a. and molar conductivities. The results show that the ligand coordinates to transition metal ions in the enolic form, accompanied by the release of acetate or nitrate.     

Acetylferrocenyl-3-hydroxyl-2-naphthoylhydrazone and its transition metal complexes

Summary Acetylferrocenyl-3-hydroxyl-2-naphthoylhydrazone and its transition metal coordination compounds were prepared. The composition and properties of the ligand and the nature of metal to ligand bonding in its coordination compounds were characterized by elemental analyses, i.r. spectra, n.m.r. spectra, u.v.-vis. spectra, thermal analyses and molar conductivities.     

Spectral, magnetic and biological studies of 1,4-dibenzoyl-3-thiosemicarbazide complexes with some first row transition metal ions

The ligand 1,4-dibenzoyl-3-thiosemicarbazide (DBtsc) forms complexes [M(DBtsc-H)(SCN)] [M = Mn(II), Co(II) or Zn(II)], [M(DBtsc-H) (SCN)(H₂O)] [M = Ni(II) or Cu(II)], [M(DBtsc-H)Cl] [M = Co(II), Ni(II), Cu(II) or Zn(II)] and [Mn(DBtsc)Cl₂], which have been characterized by elemental analyses, magnetic susceptibility measurements, UV/Vis, IR,¹H and¹³C NMR and FAB mass spectral data. Room temperature ESR spectra of the Mn(II) and Cu(II) complexes yield <g> values, characteristic of tetrahedral and square planar complexes respectively. DBtsc and its soluble complexes have been screened against several bacteria, fungi and tumour cell lines.     

DFT characterization of 1-acetylpiperazinyl-dithiocarbamate ligand and its transition metal complexes

Employing DFT and handling the solvent effects with the PCM model, the 1-acetylpiperazinyldithiocarbamate acpdtc ligand and its M(acpdtc)₂ complexes, where M is Mn(II), Fe(II), Co(II), Ni(II) and Cu(II), are characterized computationally. The obtained results suggest that the piperazine ring adopts chair conformation in all the studied species. In the gas and solution phases, the chair form of the ligand is dominant. For the Mn, Fe and Co complexes the tetrahedral structure is more stable than the square form in the gas and solution phases. However, the Ni and Cu complexes adopt the square form, in which the complex has the inversion center. The calculated vibrational frequencies are in agreement with the experimental ones, confirming the suitability of the optimized geometries of the compounds. Atomic charges, electron distribution of the frontier orbitals, and stabilizing electron transfers are determined by the NBO analysis.     

Catalytic and biological activity of transition metal complexes of salicylaldiminopropylphosphine

Primary phosphine complexes of transition metals have been synthesized from salicylaldiminopropylphosphine. The complexes were characterized by elemental analysis, infrared, electronic, ¹H NMR, ³¹P NMR spectra, magnetic susceptibility, and conductivity measurements. The studies indicate square planar geometry for copper, cobalt, and nickel complexes. The EPR spectra of copper complex in acetonitrile at 300 and 77 K were recorded. The biological activities of the ligand and metal complexes have been studied on microorganisms such as Salmonella typhi, Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Aspergillus flavus by the well-diffusion method. The zone of inhibition values were measured at 37°C for 24 h. The electrochemical behavior of copper complexes was studied by cyclic voltammetry. The copper(II) complex oxidizes cinnamaldehyde using hydrogen peroxide as oxidant.     

Spectral, XRD, SEM and biological activities of transition metal complexes of polydentate ligands containing thiazole moiety

Metal complexes of o-vanillidene-2-aminobenzothiazole have been prepared and characterized by elemental and spectral (vibrational, electronic, 1H NMR and EPR) data as well as magnetic susceptibility measurements and thermo gravimetric analysis (TG/DTA). The low molar conductance values reveal the non-electrolytic nature of these complexes. The elemental analysis suggests that the stoichiometry to be 1:2 (metal:ligand). Magnetic susceptibility data coupled with electronic spectra suggest that two ligands coordinate to each metal atom by phenolic oxygen and imino nitrogen to form high spin octahedral complex with Co(II), Mn(II) and Ni(II). The fifth and sixth position of metal ion is satisfied with water molecules. The thermal behaviour (TG/DTA) of the synthesised complexes shows that the complexes loss water molecules in the first step followed by decomposition of the ligand. Spin Hamiltonian parameters predict a distorted tetrahedral geometry for the copper complex. XRD and SEM analysis provide the crystalline nature and the morphology of the metal complexes. The in vitro biological activity of the metal chelates is tested against the Gram positive bacteria (Bacillus amyloliquifacians) and gram negative bacteria (Pseudomonas species), fungus (Aspergillus niger) and yeast (Sacchromyces cereviaceae). Most of the metal chelates exhibited higher biological activities.     

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.     

Rigid ferrocenophane and its metal complexes with transition and alkaline-earth metal ions

The rigid [6]ferrocenophane, L¹, was synthesised by condensation of 1,1′-ferrocene dicarbaldehyde with trans-1,2-diaminocyclohexane in high dilution at r.t. followed by reduction. When other experimental conditions were employed, the [6,6,6]ferrocenephane (L²) was also obtained. Both compounds were characterised by single crystal X-ray crystallography. The protonation of L¹ and its metal complexation were evaluated by the effect on the electron-transfer process of the ferrocene (fc) unit of L¹ using cyclic voltammetry (CV) and square wave voltammetry (SWV) in anhydrous CH₃CN solution and in 0.1 M ⁿBu₄NPF₆ as the supporting electrolyte. The electrochemical process of L¹ between −300 and 900 mV is complicated by amine oxidation. On the other hand, an anodic shift from the fc/fc⁺ wave of L¹ of 249, 225, 81 and 61 mV was observed by formation of Zn²⁺, Ni²⁺, Pd²⁺ and Cu²⁺ complexes, respectively. Whereas Mg²⁺ and Ca²⁺ only have with L¹ weak interactions and they promote the acid-base equilibrium of L¹. This reveals that L¹ is an interesting molecular redox sensor for detection of Zn²⁺ and Ni²⁺, although the kinetics of the Zn²⁺ complex formation is much faster than that of the Ni²⁺ one. The X-ray crystal structure of [PdL¹Cl₂] was determined and showed a square–planar environment with Pd(II) and Fe(II) centres separated by 3.781(1) Å. The experimental anodic shifts were elucidated by DFT calculations on the [ML¹Cl₂] series and they are related to the nature of the HOMO of these complexes and a four-electron, two-orbital interaction.     

Synthesis, characterization and electrochemical investigation of a novel vic-dioxime ligand and its some transition metal complexes

4-(Chloroacetyl)diphenyl ether was synthesized from chloroacetyl chloride and diphenyl ether in the presence of AlCl₃ as catalyst in a Friedel-Crafts reaction. Then, its keto oxime and dioxime derivatives were prepared. 4-phenoxy-(N-4-chlorophenylamino)phenylglyoxime (H₂L) was synthesized from 4-(phenoxy)chlorophenylglyoxime and 4-chloroaniline. Ni(II), Co(II) and Cu(II) complexes of H₂L were obtained. The mononuclear Ni(II), Co(II) and Cu(II) complexes of H₂L have a metal–ligand ratio of 1:2 and the ligand coordinates through the two N atoms, as do most of the vic-dioximes. The structure of the ligand was identified by FT-IR, ¹H NMR, ¹³C NMR, ¹³C NMR (APT) spectroscopy and elemental analysis data. The structures of the complexes were characterized on the basis of FT-IR, ICP-AES, UV-Vis, elemental analysis, magnetic susceptibility measurements, and cyclic voltammetry. The electrochemical measurements were obtained by using cyclic voltammetry in DMF solution at room temperature. The electrochemical behaviors of H₂L and its complexes showed that the redox process of H₂L has one irreversible oxidation wave, whereas the redox processes of the complexes have both oxidation and reduction waves with metal centered.     

Synthesis of diferrocenylglyoxime and some of its transition metal complexes

Diferrocenylglyoxime has been prepared by the reaction of monolithioferrocene or dilithioferrocene with anti-dichloroglyoxime. Characterization of this novel vic-dioxime and some of its transition metal complexes are described.     

Synthesis,characterization of Schiff base metal complexes and their biological investigation

A new Schiff base ligand named (E)‐2‐(((3‐aminophenyl)imino)methyl)phenol (HL) was prepared through condensation reaction of m‐phenylenediamine and 2‐hydroxybenzaldehyde in 1:1 molar ratio. The new ligand was characterized by elemental analysis and spectral techniques. The coordination behavior of a series of transition metal ions named Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) with the newly prepared Schiff base ligand (HL) is reported. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV–Vis, ¹H NMR, mass, electronic spectra, magnetic susceptibility and conductivity measurements and further their thermal stability was confirmed by thermogravimetric analysis (TG). From IR spectra, it was observed that the ligand is a neutral tridentate ligand coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH₂ group. The existence, the number and the position of the water molecules was studied by thermal analysis. The molecular structures of the Schiff base ligand (HL) and its metal complexes were optimized theoretically and the quantum chemical parameters were calculated. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species (Staphylococcus aureus and Bacillis subtilis, (gram positive bacteria)), (Salmonella SP., Escherichia coli and Pseudomonas aeruginosa, (gram negative bacteria)) and fungi (Aspergillus fumigatus and Candida albicans). The complexes were found to possess high biological activities against different organisms. Molecular docking was used to predict the efficiency of binding between Schiff base ligand (HL) and both receptors of Escherichia coli (3 T88) and Staphylococcus aureus (3Q8U). The receptor of Escherichia coli (3 T88) showed best interaction with Schiff base ligand (HL) compared to receptor of Staphylococcus aureu (3Q8U).     

Spectroscopic studies and biological evaluation of some transition metal complexes of Schiff-base ligands derived from 5-arylazo-salicylaldehyde and thiosemicarbazide

Synthesis and spectroscopic characterization of Schiff-base complexes of Cu(II), Ni(II), and Mn(II) resulting from condensation of salicylaldehyde derivatives with thiosemicarbazide [PHBT = 1-(5-(2-phenyldiazenyl)-2-hydroxybenzylidene)thiosemicarbazide, CHBT = 1-(5-(2-(2-chlorophenyl)diazenyl)-2-hydroxybenzylidene)thiosemicarbazide, and MHBT = 1-(5-(2-p-tolyldiazenyl)-2-hydroxybenzylidene)thiosemicarbazide] are discussed. The solid complexes were confirmed by elemental analysis (CHN), molar conductance, and mass spectra. Important infrared (IR) spectral bands corresponding to the active groups in the three ligands, ¹H-NMR and UV-Vis spectra and thermogravimetric analysis were performed. The dehydration and decomposition of [Cu(PHBT)(H₂O)], [Ni(PHBT)(H₂O)] · 2H₂O, [Mn(PHBT)(H₂O)] · H₂O, [Cu(CHBT)(H₂O)], [Ni(CHBT)(H₂O)] · H₂O, [Mn(CHBT)(H₂O)] · H₂O, [Cu(MHBT)(H₂O)], [Ni(MHBT)(H₂O)] · 2H₂O, and [Mn(MHBT)(H₂O)] · 2H₂O complexes were studied. The ligands are tridentate forming chelates with 1 : 1 (metal : ligand) stoichiometry. The molar conductance measurements of the complexes in DMSO indicate non-electrolytes. The biological activities of the metal complexes have been studied against different gram positive and gram negative bacteria.     

Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes

A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, (1)H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand.     

Mesoionic thiazol-5-ylidenes as ligands for transition metal complexes

The first examples of thiazol-5-ylidene complexes featuring group 9, 10 and 11 metal centers, have been prepared by deprotonation of a series of 2,3,4-triaryl-susbtituted thiazolium salts in the presence of the corresponding transition metal precursor.     

A novel tetraoxime and its dinuclear and tetranuclear transition metal complexes

A new bis(dioxime) ligand (H₄L) containing the diphenyl ether moiety has been prepared by reacting 3,3,4,4-tetraaminodiphenyl ether (1) with 2,3-butanedione monoxime (2). Dinuclear copper(II) and cobalt(III) complexes of H₄L exhibit a metal–ligand ratio of 2:1 and the ligand coordinates through the 4 nitrogen atoms, as do most bis(dioximes). The [Cu₂(H₂L)](ClO₄)₂ molecule coordinates to the other two copper(II) ions through the deprotonated oximate oxygens to yield a tetranuclear structure, doubly-bridged by the oximate groups in a cis arrangement. The structure of bis(dioxime) and its complexes were identified by elemental analyses, ¹H-, ¹³C-n.m.r, i.r and m.s. spectral data.     

Chemistry and biological activities of CO-releasing molecules (CORMs) and transition metal complexes

The advent of CO as a small molecule that, in addition to NO, elicits essential biological functions has initiated the search for compounds and complexes capable of releasing CO in a well defined manner under physiological conditions. Since some pharmacological and therapeutic effects of CO have been established in preclinical studies, tailor-made CO-releasing molecules (CORMs) which could be utilized as pharmaceuticals could be of great benefit for many patients. Release of CO(2) is one of the most common features in chemistry and NO producing molecules are very well established but compounds with CO-releasing properties are rare. Some of the more promising candidates and molecules under study are discussed in this article. Furthermore, molecules that possess intrinsic features to serve as potential CO-RMs and merit in depth investigations are proposed. The focus is thereby on main group compounds and on transition element complexes. It should be emphasized that CORMs not only have encouraging prospects as therapeutic agents but may also be significant for synthetic pathways to novel complexes containing the CO ligand. To underline the prospects of CORMs, the chemical part is embedded in a biological and medicinal context.     

Nucleobase-containing transition metal complexes as building blocks for biological markers and supramolecular structures

The incorporation of metal complexes into nucleobases, nucleosides and nucleotides has provided a focus for the development of many novel compounds with a wide range of applications. In this perspective article the different methods to incorporate transition metal complexes into these species will be described. Applications of these compounds as biological markers, catalysts and how the hydrogen bonding properties may be employed in directing supramolecular assembly in both the solid state and solution will be discussed.     

Heterotrimetallic and heterotetrametallic transition metal complexes

The synthesis of the ruthenium σ-acetylides (η⁵-C₅H₅)L₂Ru-CC-bipy (4a, L = PPh₃; 4b, L₂ = dppf; bipy = 2,2′-bipyridine-5-yl; dppf = 1,1′-bis(diphenylphosphino)ferrocene) is possible by the reaction of [(η⁵-C₅H₅)L₂RuCl] (1) with 5-ethynyl-2,2′-bipyridine (2a) in the presence of NH₄PF₆ followed by deprotonation with DBU. Heterobimetallic Fc-CC-NCN-Pt-CC-R (10a, R = bipy; 10b, R = C₅H₄N-4; Fc = (η⁵-C₅H₅)(η⁵-C₅H₄)Fe; NCN = [1,4-C₆H₂(CH₂NMe₂)₂-2,6]⁻) is accessible by the metathesis of Fc-CC-NCN-PtCl (9) with lithium acetylides LiCC-R (2a, R = bipy; 2b, R = C₅H₄N-4).The complexation behavior of 4a and 4b was investigated.Treatment of these molecules with [MnBr(CO)₅] (13) and {[Ti](μ-σ,π-CCSiMe₃)₂}MX (15a, MX = Cu(NCMe)PF₆; 15b, MX = Cu(NCMe)BF₄; 16, MX = AgOClO₃; [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti), respectively, gave the heteromultimetallic transition metal complexes (η⁵- C₅H₅)L₂Ru-CC-bipy[Mn(CO)₃Br] (14a: L = PPh₃; 14b: L₂ = dppf) and [(η⁵-C₅H₅)L₂Ru-CC-bipy{[Ti](μ-σ,π-CCSiMe₃)₂}M]X (17a: L = PPh₃, M = Cu, X = BF₄; 17b: L₂ = dppf, M = Cu, X = PF₆; 18a: L = PPh₃, M = Ag, X = ClO₄; 18b: L₂ = dppf, M = Ag, X = ClO₄) in which the appropriate transition metals are bridged by carbon-rich connectivities.The solid-state structures of 4b, 10b, 12 and 17b are reported. The main structural feature of 10b is the square-planar-surrounded platinum(II) ion and its linear arrangement. In complex 12 the N-atom of the pendant pyridine unit coordinates to a [mer,trans-(NN′N)RuCl₂] (NN′N = 2,6-bis-[(dimethylamino)methyl]pyridine) complex fragment, resulting in a distorted octahedral environment at the Ru(II) centre. In 4b a 1,1′-bis(diphenylphosphino)ferrocene building block is coordinated to a cyclopentadienylruthenium-σ-acetylide fragment. Heterotetrametallic 17b contains a (η⁵-C₅H₅)(dppf)Ru-CC-bipy unit, the bipyridine entity of which is chelate-bonded to [{[Ti](μ-σ,π-CCSiMe₃)₂}Cu]⁺. Within this arrangement copper(I) is tetra-coordinated and hence, possesses a pseudo-tetrahedral coordination sphere.The electrochemical behavior of 4, 10b, 12, 17 and 18 is discussed. As typical for these molecules, reversible oxidation processes are found for the iron(II) and ruthenium(II) ions. The attachment of copper(I) or silver(I) building blocks at the bipyridine moiety as given in complexes 17 and 18 complicates the oxidation of ruthenium and consequently the reduction of the group-11 metals is made more difficult, indicating an interaction over the organic bridging units.The above described complexes add to the so far only less investigated class of compounds of heteromultimetallic carbon-rich transition metal compounds.