A new Schiff-base ligand is prepared by a two-step reaction of 3-formylsalicylic acid and (1R, 2R)-diaminocyclohexane in alcoholic solvents. The 1:1 condensation product exists as a zwitterion in the solid state and forms pleated hydrogen-bonded sheets. Metalation of the ligand with divalent iron, nickel, cobalt, and zinc resulted in the formation of double-stranded monohelices with exclusively M-helicity. Each complex has two tridentate ligands, with the carboxylic acid groups remaining uncoordinated. In the crystal lattice, these complexes form extended M-helical strands through intermolecular hydrogen bonding interactions. Metalation of the ligand with copper salts resulted in a distinctly different type of complex, in which the ligand has transformed into a symmetric tetradentate salen ligand with uncoordinated carboxylic acid groups.

Double-stranded monohelical complexes from an unsymmetrical chiral Schiff-base ligand.

A series of transition and non-transition metal complexes from a N4O2 hexadentate Schiff base ligand: Synthesis, spectroscopic characterization and efficient antimicrobial activities

Thiazolidine-4-carboxylic acid derivative (L) derived by condensation of D-penicillamine and 3-methoxy salicylaldehyde was used in synthesis of a copper complex (CuL). The ligand and Cu(II) complex were characterized by elemental analysis and spectral techniques. The DNA binding properties of L and CuL with calf thymus DNA were investigated by various techniques. The ability of compounds to break pUC19 DNA was checked by gel electrophoresis. The radical-scavenging activity was studied using 2,2-diphenyl-1-picrylhydrazyl assay. The ligand and CuL exert cytotoxicity against HCT116 cell line. The compounds were screened for antimicrobial activity against several microorganisms. The effect of the CuL on the surface of penicillium was analyzed by scanning electron microscopy.

DNA binding, nuclease, and colon cancer cell inhibitory activity of a Cu(II) complex of a thiazolidine-4-carboxylic acid derivative

The thiosemicarbazide and hydrazide Cu(II) complexes, [Cu3L
 2
 1
 (py)4Cl2] (1), [Cu(HL2)py] (2) and [Cu(HL3)py] (3), (H2L1 = 1-picolinoylthiosemicarbazide, H3L2 = N′-(2-hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide, H3L3 = 2-hydroxy-N′-((2-hydroxy-naphthalen-1-yl)methylene)benzohydrazide) have been prepared and characterized through physicochemical and spectroscopic methods as well as X-ray crystallography. Complex 1 has a centrosymmetric structure with –N–N– bridged Cu3 skeleton. Neighboring molecules are linked into a 3D supermolecular framework by π–π stacking interactions, N–H···Cl and C–H···Cl hydrogen bonds. Complexes 2 and 3 have similar planar structures but different dimers formed by concomitant Cu···N and Cu···O interactions, respectively. Solvent accessible voids with a volume of 391 A3 are included in the structure of complex 2, indicating that this complex is a potential host candidate. Thermogravimetric analysis shows that the three complexes are stable up to 100 °C.

Synthesis, structural characterization and thermal properties of three copper(II) complexes based on aryl hydrazide ligands

The polymer-anchored Schiff base complexes of Cu(II), Co(II), Ni(II), Mn(II) and Fe(III) were prepared by reacting polystyrene amine with 2-pyridinecarbaldehyde followed by loading of metal atom in methanol. These complexes were characterized by using different physico-chemical and spectroscopic methods. The catalytic activity of these polymer-supported metal catalysts was tested for the oxidation of various olefins and alcohols. Influence of various reaction parameters, such as reaction temperature, reaction time, oxidant, substrate-to-oxidant mole ratio and nature of solvent, was studied for the oxidation of cyclohexene with these catalysts. Among the catalysts studied, Cu-Cat showed higher catalytic activity toward oxidation reactions than the other catalysts. Moreover, hot filtration experiments proved that these catalysts are truly heterogeneous and can be reused a number of times without significant loss of activity.

Synthesis, characterization and catalytic activity of polymer anchored transition metal complexes toward oxidation reactions

The reaction of 3-formylsalicylic acid with morpholine N-thiohydrazide in ethanol leading to the formation of a new thiohydrazone, 3-carboxy-2-hydroxybenzaldehydemorpholine N-thiohydrazone (H2chbmth) is described. This thiohydrazone ligand remained as the thio-keto form in the solid state. However, thioketo- and a small amount of the thiol-tautomeric forms (H2chbmth and H3chbmthol, respectively) remain in equilibrium in solution. The reactions of the ligand with different metal salts (in 1 : 1 molar ratio) leading to the synthesis of many new metal complexes have been studied. Depending on pH of the reaction medium and the nature of the metal salt used, the ligand is found to be monobasic tridentate, dibasic tridentate, monobasic bidentate or neutral bidentate giving complexes [Co(H2chbmth)2]X2, [X = NO3 (11), ½SO4 (13)]; [Cd(H2chbmth)(H2O)2]SO4 (21); [M(Hchbmth)X], [M = Cu(II) and X = Cl (1), NO3 (2), CH3COO (4); M = Ni(II) and X = Cl (6), NO3 (7); M = Co(II) and X = NO3 (12), CH3COO (14); M = Zn and X =...

Synthesis and characterization of a new thiohydrazone ligand, 3-carboxy-2-hydroxybenzaldehydemorpholine N-thiohydrazone and its metal complexes

The reaction of 3-formylsalicylic acid with 2-aminoethanethiol produces 2-(1-carboxyl-2-hydroxyphenyl)thiazolidine (H2chptz) which remains in equilibrium in solution with its corresponding Schiff base, 3-carboxysalicylidenethioethanolimine (H3mcsalim) having an NSO-donor set of atoms. The reactions of the thiazolidine ligand with different metal salts leading to the synthesis of many new metal complexes and organometallic derivatives have been studied. For all the complexes the dianion of the Schiff base, H3mcsalim acts as a tridentate NSO donor ligand. The reactions of [(Hmcsalim)Ti(π-C5H5)Cl] and [(Hmcsalim)Sn(Me)Cl], isolated in this study, with Me3SiE (where, E stands for SMe, NMe2 and C≡CPh) have also been studied. The elemental analyses, magnetic susceptibilities, molar conductance values, EPR-study, CV, molecular weights and spectroscopic (UV-Vis, IR, 1H NMR) data characterize all the compounds under study. Based upon these data the geometry of the compounds has also been proposed.

Synthesis, characterization and coordination behavior of 2-(1-carboxyl-2-hydroxyphenyl)thiazolidine

Reactions of l·formylfcrrocene-4-methoxybcnzoylhydrazonc · (HFfmhh) and l-acctylfcrroccnc-4·mcthoxybcnzoylhydrazonc (HA!'m hh) with TiCI4(thf)z, ZrCI~(thf)z, (thf = tetrahydrofuran), (n:-CsHs)TiCb, (n:-CsHs)TiCh(OMe), TiC!z(OMc)z :md (n:-CsHs)2ZrCh yield complexes of the types (Lig)zTiCh, (Lig)ZrCh(thf), (7t-CsHs)Ti(LighX, Ti(Lig)2X2 and (7t·CsHs)Zr(Lig)2CI (where HLig = HFfmbh and HAfmbh; 'x = Cl and OMe). Reaction of (Ffmbh)2TiCh with LiMe in benzene yields dimethyl derivative (FfmbhhTiMez, while that of (l'fmhhhTiCiz with l'hMgllr in the affords org:motitanium(llll species (Ffmbh)2Ti(Ph)thf. On the other hand, reactions of (n:-CsHs)Ti(FfmbhhCI, also synthesized in this study, with MeSH, Me3Si(NMc2), McJSi(N3) and Me3SiC=C-Ph afford (n:CsHs)Ti(Ffmbh)zL 1 (where I} = SMc, NMez, N3 :md -C;;;;C-I'h). Hoth the ligands function in a monobasic hidentate fashion in the complexes and the deprotonatcd cnolic form of the ligand is involved in the coordination to the metal.

Sanjib Mukhopadhyay

Papers

Synthesis and characterization of a new thiohydrazone ligand, 3-carboxy-2-hydroxybenzaldehydemorpholine N-thiohydrazone and its metal complexes

Synthesis, characterization and coordination behavior of 2-(1-carboxyl-2-hydroxyphenyl)thiazolidine

Ferrocene-derived ligands and their reactions with titanium, organotitanium, zirconium and organozirconium compounds