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Abstract
Some isonicotinoyldithiocarbazate complexes of nickel(II) and copper(II), of general formulae M(IN-Dtcz)2, [M(IN-DtczH)2]Cl2, and [M(IN-DtczH-Sal)2]Cl2 (M = Ni(II), Cu(II); INDtcz = isonicotinoyldithiocarbazate; IN-DtczH = isonicotinoyldithiocarbazic acid; IN-DtczH-Sal = 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]Cl2 exhibit NS linkage of the ligands, while Cu(IN-Dtcz)2 and [Cu(IN-DtczH)2]Cl2 have ONS binding of the ligands. The nickel(II) dithiocarbazates have [NiN2S2] 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]Cl2 and [Ni(IN-DtczH-Sal)2]Cl2. Copper(II) dithiocarbazates, namely Cu(IN-Dtcz)2, [Cu(IN-DtczH)2]Cl2, with ONS ligands having dimeric or polymeric octahedral structures, and [Cu(IN-DtczH-Sal)2]Cl2, 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, −2J = 202.14 and 29.26 cm−1, has been evaluated for [Cu(IN-DtczH)2]Cl2 and [Cu(IN-DtczH-Sal)2]Cl2, 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]Cl2 has been attributed to different electronic and steric factors of the three ligands, that is, isonicotinoyldithiocarbazate, its acid, and salicylaldehyde Schiff-base derivative.