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Some isonicotinoyldithiocarbazate complexes of nickel(II) and copper(II), of general formulae M(IN-Dtcz) 2 , [M(IN-DtczH) 2 ]Cl 2 , and [M(IN-DtczH-Sal) 2 ]Cl 2 (M ¼ Ni(II), Cu(II); INDtcz ¼ isonicotinoyldithiocarbazate; IN-DtczH ¼ isonicotinoyldithiocarbazic acid; IN-DtczH-Sal ¼ salicylaldehyde Schiff base of isonicotinoyldithiocarbazic acid), have been synthesized. These complexes have been investigated by elemental analyses, mass, room temperature infrared and electronic spectra, and variable temperature magnetic susceptibility measurements. The three nickel(II) dithiocarbazates and [Cu(IN-DtczH-Sal) 2 ]Cl 2 exhibit NS linkage of the ligands, while Cu(IN-Dtcz) 2 and [Cu(IN-DtczH) 2 ]Cl 2 have ONS binding of the ligands. The nickel(II) dithiocarbazates have [NiN 2 S 2 ] chromophore. Magnetic and solution electronic absorption spectral data reveal square-planar geometry for Ni(IN-Dtcz) 2 and the existence of square-planar-tetrahedral equilibrium for [Ni(IN-DtczH) 2 ]Cl 2 and [Ni(IN-DtczHSal) 2 ]Cl 2 . Copper(II) dithiocarbazates, namely Cu(IN-Dtcz) 2 , [Cu(IN-DtczH) 2 ]Cl 2 , with ONS ligands having dimeric or polymeric octahedral structures, and [Cu(IN-DtczH-Sal) 2 ]Cl 2 , with NS binding having dimeric square-planar structure, exhibit antiferromagnetism. Superexchange pathway involving the bridging nitrogen and sulfur of the isonicotinoyldithiocarbazate ligands rather than direct metal-metal exchange is suggested for antiferromagnetic interactions. The spin exchange parameter, À2J ¼ 202.14 and 29.26 cm À1 , has been evaluated for [Cu(IN-DtczH) 2 ]Cl 2 and [Cu(IN-DtczH-Sal) 2 ]Cl 2 , respectively, while it could not be evaluated for Cu(IN-Dtcz) 2 because the slope was negative due to the non-variation of its magnetic moment with temperature. The difference in antiferromagnetic behavior and inconsistency of 2J for [Cu(IN-DtczH-Sal) 2 ]Cl 2 has been attributed to different electronic and steric factors of the three ligands, that is, isonicotinoyldithiocarbazate, its acid, and salicylaldehyde Schiff-base derivative.

An isonicotinoyldithiocarbazic acid (IN-DtczH) ligand, synthesized from isoniazid, was complexed with transition metals and evaluated for anti-mycobacterial activity as well as toxicity towards human-transformed rhabdomyosarcoma (RD) cells in vitro. Complexes with Ni, Co and Zn showed MIC of 2, 2 and 50 mug/ml against Mycobacterium tuberculosis H(37)Rv, and 10, 100 and 50 mug/ml against a multidrug-resistant strain of M. tuberculosis. They had little cytotoxic effect on the RD cells. In contrast, the Cu complex was highly cytotoxic with a low anti-mycobacterial activity.

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