Spectroscopic, magnetic, and electrochemical studies of a dimeric N-substituted-sulfanilamide copper(II) complex. X-ray and molecular structure of the Cu-2(sulfathiazolato)(4) complex

A copper(II) complex of formula Cu-2(stz)(4) (stz(-) = sulfathiazolato) has been synthesized and characterized by single-crystal X-ray diffraction. The compound crystallizes in the orthorhombic system, space group P2(1)cn with a = 10.595(7) Angstrom, b = 14.274(3) Angstrom, c = 29.65(1) Angstrom, and Z = 4. The structure consists of dinuclear copper(II) units which contain four sulfathiazolato ligands bridging the metal ions through a nonlinear NCN group. The copper atoms are four-coordinated, the chromophore being CuN4. The Cu ... Cu bond distance is 2.671(2) Angstrom. Magnetic susceptibility data in the temperature range 7-300 K show the occurrence of intramolecular antiferromagnetic coupling with 2J = -61.5 cm(-1). This low exchange energy value has been analyzed and rationalized through extended Huckel calculations. EPR spectra at X- and Q-band frequencies show the signals corresponding to a dinuclear entity, being the zero-field splitting parameter, D = 0.230 cm(-1).