Synthesis, spectral and kinetic studies of copper(II) thiocarboxylates as molecular precursor for metal sulfide

504-510A series of binary and ternary copper(II) complexes of thiocarboxylic acids and straight chain fatty acids with general formula Cu(SOCR)2(EtOH) and Cu(SOCR)(OOCR')(EtOH) [where R = CH3 or C6H5 and R' = C7H15, C11H23 or C13H27] have been synthesized and characterized. The binary copper(II) complexes have been investigated for their potential to act as precursors for the formation of metal sulfide materials. These species are expected to undergo thiocarboxylic anhydride elimination to give stoichiometric metal sulfides and remove the organic supporting ligands cleanly. The complexes are characterized by elemental and thermo gravimetric analyses, spectral (IR, UV/Visible and ESR) and molar conductivity studies, molecular weight and magnetic moment measurements. The spectroscopic and analytical data have been found to be consistent with the identified formulae and the compounds are dimeric with bridging mode of coordination of the ligands. Magnetic data and ESR studies suggest strong antiferromagnetic coupling between two copper atoms. Thermal decomposition of binary copper(II) complexes in the solid state results in the formation of CuS at low temperature as seen by powder X-ray diffraction studies. The kinetic parameters of these complexes have been investigated on the basis of the respective thermal curves. The values of the activation energy (Ea) of thermal decomposition, reaction order (n), frequency factor (A) and velocity constant (k) (in the Arrhenius kinetic equation), have been established from the thermal data. The preliminary studies reveal the great potential of this highly tailorable chemical system as precursors to metal sulfido species

Synthesis, structure, DNA-binding and photocleavage activity of a binuclear copper(II) complex

643-649A binuclear copper(II) complex [Cu(L)(NO₃)]₂ (1), where L is a NSO-donor reduced Schiff base ligand derived from salicylaldehyde and 2-mercaptoethylamine, is prepared, structurally characterized as 10.5MeCN by single crystal X-ray diffraction method and its DNA binding and photo-induced DNA cleavage activity studied. Complex 1 has a diphenoxo-bridged binuclear structure with a {Cu₂(μ-OAr)₂} core showing CuNO₃S coordination at each metal centre. The redox active complex displays two quasi-reversible cyclic voltammetric responses at 0.26 V (ΔEp = 390 mV) and at 0.078 V (ΔEp = 375 mV) versus SCE in DMF-0.1 M TBAP at scan rate of 50 mV s⁻¹. The complex exhibits a d-d band at 661 nm in DMF and shows moderate binding propensity to calf thymus DNA. It cleaves supercoiled (SC) DNA in the presence of 3-mercaptopropionic acid as a reducing agent. The complex is active in showing photo-induced cleavage of supercoiled pUC19 DNA in UV light of 365 nm and red light of 633 nm (He-Ne laser). The DNA photocleavage reaction involves formation of singlet oxygen (¹O₂) as the reactive species in a type-II pathway

Synthesis, spectral and magnetic studies of some polynuclear, mixed-ligand complexes of iron and cobalt with 3-mercaptopropionic acid

1905-1909Some mixed-ligand, trinuclear complexes of mixed-valence iron (III, III, II) and dinuclear cobalt(II) have been synthesized by enforced substitution of acetate ions from their respective acetate complexes. The isolated products of the types [Fe3O(OOCR)3(OOCR'SH)3] and [Co(OOCR)(OOCR'SH)]2(where R = C7H15, C11H23 or C15H31 and R' = -CH2CH2-) are mixed (carboxylato)(mercaptocarboxylato) complexes. These have been characterized by microanalytical data and infrared, UV visible and Mossbauer spectra. Non-electrolytic behaviour and polynuclear nature of the complexes have been assessed from their low conductance and high molecular weight data. The octahedral environment around both the metals has been suggested on the basis of UV-visible and magnetic moment data. Mossbauer studies reveal two resolved quadrupole doublets due to Fe(II) and Fe(III) confirming the valence-localised classification of the iron compounds

Bis(dipyridophenazine)copper(II) complex as major groove directing synthetic hydrolase

The copper(II) complex $[Cu(dppz)_2Cl]Cl$ (1) has been prepared, structurally characterized and its DNA binding and cleavage properties studied (dppz, dipyridophenazine). Crystal structure of $1·dppz·H_2O$ shows the presence of the monocationic copper(II) complex containing two dppz ligands and one chloride in the five coordinate structure. While one bidentate chelating dppz ligand occupies the basal plane, the other dppz ligand shows an axial/equatorial mode of bonding. The chloride ligand binds at the basal plane. The complex crystallizes with dppz and water as lattice molecules. The dppz moieties in the metal-bound and free forms are involved in $\pi - \pi$ stacking interactions. The one-electron paramagnetic complex shows a visible spectral d–d band at 707 nm in DMF and displays quasireversible cyclic voltammetric response for the Cu(II)/Cu(I) couple near 0.1 V vs. SCE in DMF-0.1 M TBAP. The complex which is an avid binder to calf thymus DNA giving a binding constant $(K_b)$ value of $2.0\times10^4 M^{-1}$ in DMF–Tris buffer, cleaves supercoiled pUC19 DNA in an oxidative manner in the presence of mercaptopropionic acid (MPA) as a reducing agent or on photo irradiation at 312 nm. Control experiments show major groove binding and DNA cleavage via the formation of hydroxyl radical in the presence of MPA and by singlet oxygen in the photocleavage reaction. The complex exhibits significant hydrolytic cleavage of DNA in the dark in the absence of any additives at a rate of ~3.0 $h^{-1.}$ The hydrolytic nature of the DNA cleavage is evidenced from the T4 ligase experiments converting the nicked circular form to its original supercoiled form quantitatively. Complex 1 presents a rare example of copper-based major groove directing efficient synthetic hydrolase

Synthesis and characterization of hydroxycarboxylato complexes of nickel(II)

320-322Acetate groups of anhydrous nickel(II) acetate have been substituted with some higher carboxylic acids and hydroxycarboxylic acids in toluene under reflux and the products Ni(OOCR)(OOCR'), Ni(OOCR) (OOCR") and Ni(OOCR)(OOCR"') [where R=C13H27, C17H35 or C21H43 and R'=C6H4OH, Rʹʹ = C6H5CH(OH) and R'" = (C6H5)2C(OH)] obtained have been characterized by elemental analyses, electronic and IR spectra and conductivity measurements. An octahedral environment around nickel(II) ion is suggested and the molecular weight determinations confirm the dinuclear nature of these complexes

Synthesis and characterization of ternary carboxylato complexes of cobalt(II) with Schiff bases

2006-2010Some novel mixed-ligand, ternary carboxylato complexes of cobalt(II) with Schiff bases (HSB) having general formula [Co(OOCR)(SB)] (where R = C11H23, C13H27, C15H31 or C17H35) have been synthesized by the substitution reactions of anhydrous cobalt(II) acetate. The isolated products have been characterized by elemental analyses, molar conductance and magnetic moment measurements and spectral (infrared, electronic and FAB mass) data. Models and coordination hypotheses for the complexes have been proposed and a peculiar structural characterization has been discussed on the basis of physicochemical studies. A sharp structural change has been noticed

Effect of copper-sulphur bond on the DNA photo-cleavage activity of 2-(methylthio)ethylpyridine-2-carbaldimine copper(II) complexes

The binding and photo-induced DNA cleavage activity of a binary complex $[CuL_2](ClO_4)_2$ (1) and the in situ generated ternary complexes $[CuLB](ClO_4)_2$ from 1 (B: 1,10-phenanthroline, phen, 2;dipyrido[3,2-d: 2',3'-f]quinoxaline, dpq, 3) are studied, where L is a $N_2S-donor$ tridentate Schiff base2(methylthio)ethylpyridine-2-carbaidimine. Complex 1, structurally characterized by X-ray diffraction study, has six-coordinate meridional geometry showing $CuN_4S_2$ coordination. The Cu-N bond lengths are in the range of 1.968(3) to 2.158(4) angstrom. The Cu-S bond lengths of2.599(2) and 2.705(2) angstrom are significantly long indicating weakcovalent interaction between copper and sulphur atoms. The thiomethylgroups are cis to each other giving S-Cu-S angle of 75-82(5)degrees.The Cu-N(pyridyl) bond distances are longer than the Cu-N(imine) bonds.The complexes are redox active and display a quasi-reversible cyclicvoltammetric response assignable to the Cu(II)/Cu(I) couple near 0.0 Vvs SCE in DMF-Tris buffer (1 : 4 v/v) using 0. 1 M KCl as supporting electrolyte. Electronic spectra of the complexes show a d-d band in therange 630 to 700 nm in DMF along with higher energy charge transfer bands. While complex 1 is a poor binder to DNA, the ternary complexess how good DNA binding propensity. The photo-nuclease activity of 1-3 isstudied using UV and visible wavelengths. The DNA cleavage activity at 365 nm follows the order: 3 > 2 > 1. The cleavage reaction involves theformation of singlet oxygen as the reactive species in a type-II process