Abstract
Several Cr(III) complexes of
l(-)cystine,
l(-)cysteine, dibenzyldisulphide, α-mercaptosuccinic acid and 5,5′-dithiobisnitrobenzoic acid were prepared and characterized by their vibrational, electronic and circular dichroism measurements. The coordination of sulphur-containing amino acids involved amino and carboxylate groups. In the visible spectra, two peaks were observed at 15 900–18 700 and 23 000–25 300 cm
−1 and were assigned to
4A
2g →
4T
2g and
4A
2g →
4T
1g (f) d-d transitions, respectively in octahedral (O
h) or pseudo-octahedral (D
3) symmetry. Three sharp Cotton effects were observed in the circular dichroism spectra of cysteine and cystine chelates and were assigned to the
2E(
2E
g),
2A
2(
2T
1g), and
2E(
2T
1g) d-d transitions. The observed Cotton effects in the allowed band arise from the splitting of
4A
2g →
4T
2g to
4A
1(
4T
2g) and
4E(
4T
2g) transition. The parameters D
q, B, β
35 and the variation of interelectronic repulsion value with ionic charge, Z
∗ for the complexes were calculated. The magnetic moments (3.6–3.9 B.M) are close to the spin-only value for a d
3 Cr(III) ion in octahedral symmetry. Cyclic voltammetry experiments on some of the complexes revealed a reversible Cr(III)/Cr(II) redox couple and pronounced solvent and scan rate effects on the peak potentials and peak currents.