Abstract
Chromium(III) complexes prepared from CrCl
3Py
3 and anhydrous CrCl
3 with
l(−)-threonine, nicotinic acid, glycine,
d(−)-penicillamine,
l(−)-cysteine and
l(−)-cystine have been characterized. The magnetic moments (3.4−4.05 B.M.) are close to the spin only value for a
d
3 chromium(III) ion in octahedral or pseudo octahedral symmetry. In the electronic spectra two sharp peaks are observed at (15.9−19.8) × 10
3 and (22.0−26.7) × 10
3 cm
−1 and are assigned to
d-d transitions in the pseudo octahedral configuration. The parameters (
D
q
,
B,
β
35) and the interelectronic repulsion parameter with the ionic charge,
Z∗, are calculated and place the ligand in the middle of the spectrochemical series. In the circular dichroism spectra three Cotton effects are observed in the forbidden band of the optically active chelates and are assigned to the
2E(
2Eg),
2A
2(
2T
1g)
and
2E(
2T
1g)
while that in the spin allowed band are a result of the splitting of the
4A
2g(
4T
2g)
to
4A
1(
4T
2g)
and
4E(
4T
2g)
transitions. The structure of threonine, cystine and cysteine chelates are likely to be
fac since strong and well defined Cotton effects are observed. The Cotton effects of penicillamine chelates are weak suggesting formation of the
mer structure. Prolonged heating or bubbling air through the solution of CrCl
3Py
3 containing
l(−)-threonine, glycine or nicotinic acid for several hours enhances chromium(VI) formation.