Synthesis and characterization of some biologically active ruthenium(II) complexes of thiosemicarbazones of pyridine 2-aldehyde and thiophene 2-aldehyde involving some ring substituted 4-phenylthiosemicarbazides and 4-cyclohexylthiosemicarbazide. Crystal structure of cis-[Ru(PPh 3) 2(L 6H) 2](ClO 4) 2·2H 2O [L 6H=4-(cyclohexyl) thiosemicarbazone of pyridine 2-aldehyde

Abstract

A series of ruthenium(II) complexes of potentially NNS tridentate but functionally NS bidentate chelating ligands in the form of 4-substituted 4-phenyl and 4-cyclohexyl thiosemicarbazones of pyridine 2-aldehyde and thiophene 2-aldehyde (LH) have been synthesized using Ru(PPh 3) 3Cl 2 as the starting material. The complexes are of the general formula [Ru(PPh 3) 2(LH) 2]X 2, [L 1H, L 2H, L 3H, L 4H, L 5H and L 6H are 4-( p-fluorophenyl), 4-( p-chlorophenyl) 4-( p-iodophenyl), 4-( p-hydroxyphenyl), 4-( p-methylphenyl) and 4-( p-cyclohexyl) thiosemicarbazones of pyridine 2-aldehyde and L 7H is the 4-cyclohexyl thiosemicarbazone of thiophene 2-aldehyde (Figure 1) and X=ClO 4, PF 6]. A complex [Ru(bipy)(L 6H) 2](ClO 4) 2, has also been synthesized. All the complexes were characterized by elemental analyses, measurement of conductance in solution, magnetic susceptibility at room temperature and by spectroscopic techniques. Electrochemical behavior of the complexes has been examined by cyclic voltammetry. Structure of one of the complexes cis-[Ru(PPh 3) 2(L 6H) 2](ClO 4) 2·2H 2O, has been solved by single crystal X-ray diffraction technique. All the ligands are found to be chelated to the ruthenium(II) center in its thione form through its imine nitrogen and the thione sulfur. The pyridine ring nitrogen remained uncoordinated. The two PPh 3 molecules are situated cis to each other. All the complexes are found to exhibit biological activity in terms of Escherichia coli growth-inhibition capacity and two of them hold the possibility of displaying antitumor activity.