Macrocyclic cobalt(III) complexes as precursors for metal-polythiophene hybrid materials

A thiophene-functionalised macrocyclic ligand trans-6,13-dimethyl-6-((thiophen-3-ylmethyl)amino)-1,4,8,11-tetraazacyclotetradecane-13-amine (L¹) has been prepared and complexed with Co^III. The ligand L¹ binds as a pentadentate in the crystallographically characterised complexes [CoL¹(OAc)](ClO₄)₂ and [CoL¹Cl]Cl₂. Electro-copolymerisation of [CoL¹Cl]Cl₂ with 3,4-ethylenedioxythiophene (EDOT) in a 1:2 ratio on a preformed poly-3,4-ethylenedioxythiophene (PEDOT) film resulted in metal–polymer hybrid films of high quality, consistency and uniformity in appearance. The copolymerised films were characterised by XPS indicating a 1:11 ratio of incorporation of complex to EDOT. Electrochemistry of the Co-PEDOT film (cast on an indium-doped tin oxide working electrode) in water revealed a Co^III/II redox couple at a potential ca. −600 mV (vs Ag/AgCl) which is similar to that seen in solution for the monomeric aqua complex [CoL¹(OH₂)]³⁺.     

Crystal structure,thermal behavior,and microbiological activity of a thiosemicarbazide-type ligand and its cobalt complexes

The synthesis of a potentially bioactive mixed-valence Co^III/Co^II complex with 2-acetylpyridine S-methylisothiosemicarbazone (HL) ligand is described. The crystal and molecular structure of the formed [Co^IIIL₂][Co^IICl₃ py]·Me₂CO (I) compound (py stands for pyridine) is determined by single-crystal X-ray crystallography. It’s thermal decomposition along with the decomposition of the ligand and six structurally related complexes with formulas [CoL₂]NO₃·MeOH (1), [CoL₂]Br·MeOH (2), [CoL₂]HSO₄·MeOH (3), [CoL₂]₂[Co^II(NCS)₄] (4), [Co(HL)(L)]I₂·2MeOH (5), and [Co(HL)(L)][Co^IICl₄]·MeOH (6) was determined by simultaneous TG/DSC measurements. The decomposition pattern is evaluated using TG/DTA-MS data. The results were related to the solvent/moisture content and the decomposition mechanism of the compounds. The antimicrobial activity of the ligand and of all the complexes was tested in vitro for selected gram-negative and gram-positive bacteria and fungi. The activity of the ligand against all tested bacteria is comparable with those obtained for standard antibiotics, while it is less active against fungi. Surprisingly, the activity of the complexes is very low. The low antimicrobial activity of the complexes may be in connection with their high thermodynamic and kinetic inertness in solution. The results are also supported by the relatively high thermal stability of the complexes.     

Experimental and theoretical characterization of Co(III) and Zn(II) complexes with phenol-based hexa-dentate macro-acyclic ligands: synthesis,density functional theory and time-dependent density functional theory studies

Macro-acyclic complexes with two dissimilar coordination sites: one includes six coordination set (N₄O₂) and the other a tetradentate donor set (N₂O₂) of the type [Co^IIIL^en]ClO₄ and [Co^IIIL^tn]ClO₄ (where L^en = N,N′-bis(pyridine-2-ylmethyl)-N,N′-bis(5-bromo-3-formyl-2-hydroxybenzyl)-1,2-diaminoethane and L^tn = N,N′-bis(pyridine-2-ylmethyl)-N,N′-bis(5-bromo-3-formyl-2-hydroxybenzyl)-1,3-diaminoepropane) have been synthesized and characterized. Characterization result revealed that in the synthetic procedure of [Co^IIIL^en]ClO₄ only an isomer (trans-pyridine/cis-phenolate) among three possible geometrical isomers is formed. However, synthesis of its counterpart, [Co^IIIL^tn]ClO₄ resulted in the formation of a mixture of geometrical isomers (trans-pyridine/cis-phenolate and cis-pyridine/cis-phenolate). The computational studies of these complexes demonstrated that in [Co^IIIL^tn]⁺ an equilibrium exists between two possible geometrical isomers as result of a small energy difference (0.72 kcal mol^?1), whereas in [Co^IIIL^en]⁺ the difference is (2.71 kcal mol^?1). Furthermore, [Zn^IIL^en] has been studied computationally and experimentally by IR, UV–Vis spectroscopy techniques. The results showed that it has a similar structure to [Co^IIIL^en]⁺ complex. Electronic spectra of the complexes were analyzed and the absorption bands were assigned through the density functional theory (DFT) and time-dependent density functional theory (TD–DFT) studies procedures. The molecular orbital diagrams of the complexes were also determined.     

Ruthenium(III) and iridium(III) complexes with nicotine

A new chloride-dimethylsulfoxide-ruthenium(III) complex with nicotine trans-[Ru^IIICl₄(DMSO)[H-(Nicotine)]] (1) and three related iridium(III) complexes; [H-(Nicotine)]trans-[Ir^IIICl₄(DMSO)₂] (2), trans-[Ir^IIICl₄(DMSO)[H-(Nicotine)]] (3) and mer-[Ir^IIICl₃(DMSO)(Nicotine)₂] (4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction (1, 2, and 4). Protonated nicotine at pyrrolidine nitrogen is present in complexes 1 and 3 while two neutral nicotine ligands are observed in 4. In these three inner-sphere complexes coordination occurs through the pyridine nitrogen. Moreover, in the outer-sphere complex 2, an electrostatic interaction is observed between a cationic protonated nicotine at the pyrrolidine nitrogen and the anionic trans-[Ir^IIICl₄(DMSO)₂]^¯ complex.     

Isonitrosoacetylacetone dithiosemicarbazone complexes of some first row transition metals

Summary Complexes of the potentially tetradentate ligand isonitroso-acetylacetone dithiosemicarbazone (inbtH₂) of formulae [Ti(inbtH₂)Cl₂]Cl₂, [M(inbt)], where M = V^IV O, Mn^II, Ni^II or Zn^II, [M(inbtH₂)X₂], where M = Co^II and X = Cl, or M = Ni^II and X = Cl, Br or I, and [M(inbtH₂)Cl₂]Cl, where M = Cr^III or Fe^III, have been prepared and characterized by physico-chemical and spectroscopic methods. In all the compounds the metal is coordinated by the thiocarbonyl sulphur and imine nitrogen, as revealed by i.r. studies. The n.m.r. spectra of the complexes of Ni^II and Zn^II confirm coordination through nitrogen. Possible structures for the complexes are proposed. The Mössbauer spectrum of the Fe^III complex is discussed.     

Ruthenium(II/III)‐Based Compounds with Encouraging Antiproliferative Activity against Non‐small‐Cell Lung Cancer

Hereby we present the synthesis of several ruthenium(II) and ruthenium(III) dithiocarbamato complexes. Proceeding from the Na[trans‐Ru^III(dmso)₂Cl₄] ( 2 ) and cis‐[Ru^II(dmso)₄Cl₂] ( 3 ) precursors, the diamagnetic, mixed‐ligand [Ru^IIL₂(dmso)₂] complexes 4 and 5 , the paramagnetic, neutral [Ru^IIIL₃] monomers 6 and 7 , the antiferromagnetically coupled ionic α‐[Ru^III₂L₅]Cl complexes 8 and 9 as well as the β‐[Ru^III₂L₅]Cl dinuclear species 10 and 11 (L=dimethyl‐ (DMDT) and pyrrolidinedithiocarbamate (PDT)) were obtained. All the compounds were fully characterised by elemental analysis as well as ¹H NMR and FTIR spectroscopy. Moreover, for the first time the crystal structures of the dinuclear β‐[Ru^III₂(dmdt)₅]BF₄ ? CHCl₃ ? CH₃CN and of the novel [Ru^IIL₂(dmso)₂] complexes were also determined and discussed. For both the mono‐ and dinuclear Ru^II and Ru^III complexes the central metal atoms assume a distorted octahedral geometry. Furthermore, in vitro cytotoxicity of the complexes has been evaluated on non‐small‐cell lung cancer (NSCLC) NCI‐H1975 cells. All the mono‐ and dinuclear Ru^III dithiocarbamato compounds (i.e., complexes 6 – 10 ) show interesting cytotoxic activity, up to one order of magnitude higher with respect to cisplatin. Otherwise, no significant antiproliferative effect for either the precursors 2 and 3 or the Ru^II complexes 4 and 5 has been observed.     

Preparation and Characterization of Dinuclear Chromium(III) Complexes of a Hexadentate Tetraaza‐Dithiophenolate Ligand

The ability of the tetraaza‐dithiophenolate ligand H₂L² (H₂L² = N,N′‐Bis‐[2‐thio‐3‐aminomethyl‐5‐tert‐butyl‐benzyl]propane‐1,3‐diamine) to form dinuclear chromium(III) complexes has been examined. Reaction of Cr^IICl₂ with H₂L² in methanol in the presence of base followed by air‐oxidation afforded cis,cis‐[(L²)Cr^III₂(μ‐OH)(Cl)₂]⁺ ( 1a ) and trans,trans‐[(L²)Cr^III₂(μ‐OH)(Cl)₂]⁺ ( 1b ). Both compounds contain a confacial bioctahedral N₂ClCr^III(μ‐SR)₂(μ‐OH)Cr^IIIClN₂ core. The isomers differ in the mutual orientation of the coligands and the conformation of the supporting ligand. In 1a both Cl^? ligands are cis to the bridging OH function. In 1b they are in trans‐positions. Reaction of the hydroxo‐bridged complexes with HCl yielded the chloro‐bridged cations cis,cis‐[(L²)Cr^III₂(μ‐Cl)(Cl)₂]⁺ ( 2a ) and trans,trans‐[(L²)Cr^III₂(μ‐Cl)(Cl)₂]Cl ( 2b ), respectively. These bridge substitutions proceed with retention of the structures of the parent complexes 1a and 1b .     

Crystal structure,electrochemical and photochemical studies of the trans-[Fe(cyclam)(NO)Cl]Cl2 complex (cyclam = 1,4,8,11-tetraazacyclotetradecane)

The trans-[Fe(cyclam)(NO)Cl]Cl₂ complex was synthesized by the reaction of cis-[Fe(cyclam)Cl₂]Cl with NO gas. The X-ray structure of the complex showed that the [Fe–NO] moiety is linear, consistent with the NO⁺ character of the nitric oxide ligand. This suggestion was reinforced by the IR data, which showed the νNO at 1888 cm⁻¹. The cyclic voltammogram of the trans-[Fe(cyclam)(NO)Cl]²⁺ complex presented three electrochemical processes at −0.70, 0.08 and 0.40 V versus Ag/AgCl. The first and last redox processes are centered at the NO ligand, whereas the second is characteristic of the generated aqua species, trans-[Fe(cyclam)Cl(H₂O)]²⁺. Upon irradiation at 330 nm, pH 3.4, the title complex releases the NO moiety with the concomitant generation of the trans-[Fe(cyclam)(H₂O)Cl]⁺ complex as suggested by electronic and IR spectroscopy as well as by cyclic voltammetry technique.     

Oxidomolybdenum(VI) complexes with atrane-type [O3N] ligands

Dioxomolybdenum(VI) complex [MoO₂Cl₂(dmso)₂] reacts with a series of tetradentate O₃N-type aminoalcohol–bisphenol ligands to form oxomolybdenum(VI) complexes of type [MoOCl(Lⁿ)]. The reaction of H₃L¹ produces [MoOCl(L¹)] as two separable isomers, whereas the reaction of H₃L² or H₃L³ yields a single product. The X-ray analyses of cis- and trans-[MoOCl(L¹)] reveal that the complexes are formed of monomeric molecules. The ligands have tetradentate coordination through three oxygen donors and one nitrogen donor, which is located trans to the terminal oxo group. The sixth coordination site is occupied by a chloro ligand.     

Mono and trinuclear lanthanide complexes of 13-membered tetraaza macrocycle: Synthesis and characterization

The reaction of 1,8-diamino-3,6-diazaoctane and diethyl malonate in dry methanol yielded a 13-membered macrocycle. Complexes of the type [Ln(tatd)Cl₂ (H₂O)₃]Cl [Ln^III=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy; tatd=1, 5, 8, 11-tetra-azacyclotridecane-2,4-dione] have been synthesized by template condensation. The complex [La(tatd)Cl₂ (H₂O)₃]Cl in methanol was reacted with lanthanide chlorides to yield the trinuclear complexes of type [2{La(tatd)Cl₂(H₂O)₃}LnCl₃]Cl₂ [Ln^III=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy]. The chemical compositions of mono and trinuclear complexes have been established on the basis of analytical, molar conductance, electrospray (ES) and fast atom bombardment (FAB) mass data. In mononuclear complexes the Ln³⁺ ion is encapsulated by four ring nitrogens and in trimetallic complexes the exo-carbonyl oxygens of two mononuclear units coordinate to the Ln³⁺ ions resulting in a polyhedron around the lanthanide ions. Thus the macrocycle is bonded in a tetradentate fashion in the former complexes and hexadentate in the latter. The coordination number nine around the encapsulated Ln³⁺ and seven around the exo-oxygen bonded Ln³⁺ ions are established. The symmetry of the ligand field around the metal ions is indicated from the emission spectra.     

Cyano­cobalt(III) complexes of penta‐ and tetra­dentate‐coordinated macrocyclic hexa­amines

The pendent‐arm macrocyclic hexa­amine trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine (L) may coordinate in tetra‐, penta‐ or hexa­dentate modes, depending on the metal ion and the synthetic procedure. We report here the crystal structures of two pseudo‐octa­hedral cobalt(III) complexes of L, namely sodium trans‐cyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine)cobalt(III) triperchlorate, Na[Co(CN)(C₁₃H₃₀N₆)](ClO₄)₃ or Na{trans‐[CoL(CN)]}(ClO₄)₃, (I), where L is coordinated as a penta­dentate ligand, and trans‐dicyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diamine)cobalt(III) trans‐dicyano­(trans‐6,13‐dimethyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐6,13‐diaminium)cobalt(III) tetra­perchlorate tetra­hydrate, [Co(CN)₂(C₁₄H₃₂N₆)][Co(CN)₂(C₁₄H₃₀N₆)](ClO₄)₄·4H₂O or trans‐[CoL(CN)₂]trans‐[Co(H₂L)(CN)₂](ClO₄)₄·4H₂O, (II), where the ligand binds in a tetra­dentate mode, with the remaining coordination sites being filled by C‐­bound cyano ligands. In (I), the secondary amine Co—N bond lengths lie within the range 1.944 (3)–1.969 (3) Å, while the trans influence of the cyano ligand lengthens the Co—N bond length of the coordinated primary amine [Co—N = 1.986 (3) Å]. The Co—CN bond length is 1.899 (3) Å. The complex cations in (II) are each located on centres of symmetry. The Co—N bond lengths in both cations are somewhat longer than in (I) and span a narrow range [1.972 (3)–1.982 (3) Å]. The two independent Co—CN bond lengths are similar [1.918 (4) and 1.926 (4) Å] but significantly longer than in the structure of (I), again a consequence of the trans influence of each cyano ligand.     

Synthesis,spectroscopy and cyclic voltammetry of cobalt(III) complexes with 5-methyl-3-formylpyrazole N(4)-cyclohexylthiosemicarbazone (HMPz4Cy): X-ray crystal structure of [Co(MPz4Cy)2]Cl · 2.75H2O

The coordination behaviour of the novel ligand, HMPz4Cy, is reported, together with solid state isolation of its diamagnetic cobalt(III) complexes, [Co(MPz4Cy)₂]X · nH₂O (X = Cl, Br, NO₃, ClO₄ and BF₄). I.r. and ¹H-n.m.r. data for the free ligand and its Co^III complexes confirm that the ligand, HMPz4Cy, acts as a uninegative anion with NNS tridentate function via the pyrazolyl nitrogen (tertiary), azomethine nitrogen and thiol sulphur. Electronic spectra (both solid and solution) are commensurate with a distorted octahedral environment for the reported Co^III species. Cyclic voltammograms of Co^III complexes indicate a quasireversible Co⁺³/Co⁺² couple. X-ray crystallography of a representative species, [Co(MPz4Cy)₂]Cl · 2.75H₂O (C2, monoclinic), has shown unambiguously that the two ligands are orthogonally coordinated to the central Co^III ion with both the thiolato sulphurs and both pyrazolyl nitrogen atoms in cis positions.     

Synthesis and characterization of copper(II) and cobalt(II) complexes with two new potentially hexadentate Schiff base ligands. X-ray crystal structure determination of one copper(II) complex

Two new potentially hexadentate N₂O₄ Schiff base ligands 2-((z)-(2-(2-(2-((z)-3,5-di-tert-butyl-2-hydroxybenzylideneamino) phenoxy) phenoxy) phenylimino) methyl)-4,6-di-tert-butylphenol [H₂L¹] and 2-((z)-(2-(2-(2-((z)-3,5-di-tert-butyl-2-hydroxybenzylideneamino) phenoxy)-5-tert-butylphenoxy) phenylimino) methyl)-4,6-di-tert-butylphenol [H₂L²] were prepared from the reaction of 3,5-di-tert-butyl-2-hydroxy benzaldehyde with 1,2-bis(2′-aminophenoxy)benzene or 1,2-bis(2′-aminophenoxy)-4-t-butylbenzene, respectively. From the direct reaction of ligands [H₂L¹] and [H₂L²] with copper(II) and cobalt(II) salts in methanolic solution and in the presence of N(Et)₃ the neutral [CuL¹], [CuL²], [CoL¹] and [CoL²] complexes were prepared. All complexes were characterized by IR spectra, elemental analysis, magnetic susceptibility, mass spectra, molar conductance (Λ_m), UV-Vis spectra and in the case of [CuL²] with X-ray diffraction. X-ray crystal structure of [CuL²] showed that the complex contains copper(II) in a distorted square planar environment of N₂O₂ donors. Three CH/π interactions were observed in the molecular structure of latter complex.     

Fe(II) complex with chiral pyrazolylquinoline L and Fe(II), Co(II), and Cu(II) complexes with achiral pyrazolylquinoline L1: Synthesis and properties. The crystal structures of [ML1Cl2] (M = Fe, Co, and Cu)

The complexes FeLCl₂ (I), [FeL¹Cl₂] (II), [CoL¹Cl₂] (III), and [CuL¹Cl₂] (IV) (where L and L¹ are chiral and achiral pyrazolylquinolines, respectively) were obtained. Complexes II–IV were structurally characterized by single-crystal X-ray diffraction analysis. Crystals of complexes II and III are triclinic (space group P $ \bar 1 The complexes FeLCl₂ (I), [FeL¹Cl₂] (II), [CoL¹Cl₂] (III), and [CuL¹Cl₂] (IV) (where L and L¹ are chiral and achiral pyrazolylquinolines, respectively) were obtained. Complexes II–IV were structurally characterized by single-crystal X-ray diffraction analysis. Crystals of complexes II and III are triclinic (space group P ) and crystals of complex IV are monoclinic (space group P2₁/n). Structures II–IV are built from discrete mononuclear acentric molecules. In these complexes, the M²⁺ ion (M = Fe, Co, and Cu) coordinates two N atoms of the bidentate chelating ligand L¹ and two Cl atoms. The coordination cores MCl₂N₂ are distorted tetrahedra. For complexes I and II, μ_eff = 5.05 and 5.07 μ_B, respectively, correspond to the high-spin configuration d ⁶. For complex III, μ_eff = 4.51 μ_B (high-spin configuration d ⁷) and for complex IV, μ_eff = 1.80 μ_B (configuration d ⁹). Original Russian Text ? Z.A. Savel’eva, L.A. Glinskaya, R.F. Klevtsova, S.A. Popov, A.V. Tkachev, N.V. Semikolenova, V.A. Zakharov, S.V. Larionov, 2008, published in Koordinatsionnaya Khimiya, 2008, Vol. 34, No. 4, pp. 285–292.     

Can Serendipity Still Hold Any Surprises in the Coordination Chemistry of Mixed-Donor Macrocyclic ligands? The Case Study of Pyridine-Containing 12-Membered Macrocycles and Platinum Group Metal ions PdII,PtII, and RhIII

This study investigates the coordination chemistry of the tetradentate pyridine-containing 12-membered macrocycles L¹-L³ towards Platinum Group metal ions Pd^II, Pt^II, and Rh^III. The reactions between the chloride salts of these metal ions and the three ligands in MeCN/H₂O or MeOH/H₂O (1:1 v/v) are shown, and the isolated solid compounds are characterized, where possible, by mass spectroscopy and ¹H- and ¹³C-NMR spectroscopic measurements. Structural characterization of the 1:1 metal-to-ligand complexes [Pd(L¹)Cl]₂[Pd₂Cl₆], [Pt(L¹)Cl](BF₄), [Rh(L¹)Cl₂](PF₆), and [Rh(L³)Cl₂](BF₄)·MeCN shows the coordinated macrocyclic ligands adopting a folded conformation, and occupying four coordination sites of a distorted square-based pyramidal and octahedral coordination environment for the Pd^II/Pt^II, and Rh^III complexes, respectively. The remaining coordination site(s) are occupied by chlorido ligands. The reaction of L₃ with PtCl₂ in MeCN/H₂O gave by serendipity the complex [Pt(L³)(μ-1,3-MeCONH)PtCl(MeCN)](BF₄)₂·H₂O, in which two metal centers are bridged by an amidate ligand at a Pt1-Pt2 distance of 2.5798(3) Å and feature one square-planar and one octahedral coordination environment. Density Functional Theory (DFT) calculations, which utilize the broken symmetry approach (DFT-BS), indicate a singlet d⁸-d⁸ Pt^II-Pt^II ground-state nature for this compound, rather than the alleged d⁹-d⁷ Pt^I-Pt^III mixed-valence character reported for related dinuclear Pt-complexes.     

Synthesis,crystal structures,spectroscopic studies and antibacterial properties of a series of mononuclear cobalt(III) Schiff base complexes

New complexes of cobalt(III) with the tridentate and tetradentate Schiff base ligands: 3-methoxy-2-{(Z)[(2-hydroxyphenyl)imino]methyl}phenol (H₂L¹), 4-[(2-hydroxyphenyl)imino]-2-pentanone (H₂L²); and 2-((E)-1-(2-((E)-1-(2-hydroxy-4,5-dimethylphenyl)ethylideneamino)ethylimino)ethyl)-4,5 dimethylphenol (H₂L³), namely [Co^III(L¹)(N-MeIm)₃]PF₆ (1), [Co^III(L¹)(py)₃]ClO₄ (2), [Co(L¹)(py)₃][Co(L¹)₂] (3) and [Co^III(L²)(N-MeIm)₃]PF₆ (4) and [Co(L³)(N-MeIm)₂]PF₆ (5), were synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of the complexes were determined by X-ray crystallography. In each of these complexes, the cobalt(III) centre has a slightly distorted octahedral environment, utilizing all available coordination centres of the ligands. The complexes were also screened for in vitro antibacterial activities against four human pathogenic bacteria, and their minimum inhibitory concentrations indicated good antibacterial activities.     

Synthesis, structural features and biological activities of three asymmetric pyridazine–triazole coordination polymers

The complexes [CuL₂Cl₂]_n (1), [CoL₂Cl₂(H₂O)₂]·L (2) and [MnL₂Cl₂(H₂O)₂]·L (3) (L = 3-chloro-6-(1H-1,2,4-triazol-1-yl) pyridazine) were synthesized and characterized by physicochemical and spectroscopic methods. X-ray crystallographic analysis reveals that the Cu(II) center of complex 1 is located in a slightly distorted tetragonal pyramidal environment and bridged by chlorine atoms to generate infinite 1D chains, which are further connected into 2D supramolecular structures by C–H…Cl hydrogen bonds. The Co(II) and Mn(II) atoms in complexes 2 and 3 both have a distorted octahedral coordination sphere, and the crystal lattices include hydrogen bonds and π–π stacking interactions to yield 3D supramolecular frameworks. The antioxidant activities (influence on O₂ ^?? and ^?OH) and antibacterial activities of the ligand L and its three complexes were also investigated.     

Synthesis and Characterisation of Diruthenium Paddlewheel Compounds Bearing 2,6-Di(p-tolyl)benzoate Ligands

The mixed carboxylate diruthenium complexes trans-[Ru ₂ ^II,III (O₂CCH₃)₂(O₂CAr)₂Cl] (I) and trans-[Ru ₂ ^II,II (O₂CCH₃)₂(O₂CAr)₂] (II) (O₂CAr = 2,6-di(p-tolyl)benzoate) have been synthesised along with [Ru ₂ ^II,III (O₂CAr)₄Cl] (III) and the homoleptic complex [Ru ₂ ^II,II (O₂CAr)₄] (IV). The structures trans-[Ru₂(O₂CCH₃)₂(O₂CAr)₂Cl(thf)]·(thf) and [Ru₂(O₂CAr)₄Cl(η ¹-CH₂Cl₂)] were determined by X-ray crystallography, and display the expected paddlewheel arrangement of the carboxylate ligands around the diruthenium core. The structure of III is a rare example of a structurally characterised dichloromethane complex, highlighting the Lewis acidic nature of the diruthenium axial position. The bulky ^?O₂CAr ligand protects the axial positions from intermolecular interactions in the absence of strong nucleophiles for III and IV, and the effect this has on the electronic structure of the diruthenium core in these complexes was investigated by cyclic voltammetry, electronic absorption spectroscopy and magnetic susceptibility studies.     

Synthesis, characterization, electrochemical studies, and antibacterial activities of cobalt(III) complexes with Salpn-Tipe Schiff base ligands. Crystal structure of trans-[CoIII(L1)(Py)2]ClO4

The synthesis, characterization, spectroscopic and electrochemical properties of trans-[Co^III(L¹)(Py)₂]ClO₄ (I) and trans-[Co^III(L²)(Py)₂]ClO₄ (II) complexes, where H₂L¹ = N,N′-bis(5-chloro-2-hydroxybenzylidene)-1,3-propylenediamine and H₂L² = N,N′-bis(5-bromo-2-hydroxybenzylidene)-1,3-propylenediamine, have been investigated. Both complexes have been characterized by elemental analysis, FT-IR, UV-Vis, and ¹H NMR spectroscopy. The crystal structure of I has been determined by X-ray diffraction. The coordination geometry around cobalt(III) ion is best described as a distorted octahedron. The electrochemical studies of these complexes revealed that the first reduction process corresponding to Co(III/II) is electrochemically irreversible accompanied by dissociation of the axial Co-N(Py) bonds. The in vitro antimicrobial activity of the Schiff bse ligands and their corrsponding complexes have been tested against human pathogenic bacterias such as Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli. The cobalt(III) complexes showed lower antimicrobial activity than the free Schiff base ligands.     

Synthesis and crystal structure characterization of iron(II), cobalt(II) and nickel(II) complexes with 1,3-bis(2-pyridylmethylthio)propane

Three new mononuclear complexes of nitrogen–sulfur donor sets, formulated as [Fe^II(L)Cl₂] (1), [Co^II(L)Cl₂] (2) and [Ni^II(L)Cl₂] (3) where L = 1,3-bis(2-pyridylmethylthio)propane, were synthesized and isolated in their pure form. All the complexes were characterized by physicochemical and spectroscopic methods. The solid state structures of complexes 1 and 3 have been established by single crystal X-ray crystallography. The structural analysis evidences isomorphous crystals with the metal ion in a distorted octahedral geometry that comprises NSSN ligand donors with trans located pyridine rings and chlorides in cis positions. In dimethylformamide solution, the complexes were found to exhibit Fe^II/Fe^III, Co^II/Co^III and Ni^II/Ni^III quasi-reversible redox couples in cyclic voltammograms with E_1/2 values (versus Ag/AgCl at 298 K) of +0.295, +0.795 and +0.745 V for 1, 2 and 3, respectively.