M. Kaneyoshi et al., ADSORPTION AND SPECTROSCOPIC STUDIES ON THE INTERACTIONS OF COBALT(III) CHELATES WITH CLAYS, Clays and clay minerals, 41(1), 1993, pp. 1-6
The interactions of the following three kinds of racemic and enantiome
ric cobalt(III) chelates with montmorillonite and saponite are studied
: [Co(en)3]3+ (en = ethylenediamine), [Co(diNOsar)]3+ (diNOsar = ,19-h
exaazabicyclo[6,6,61-eicosane)cobalt(III))and [Co(diAMsar)]3+ (diAMsar
= 6,19-hexaazabicyclo-[6,6,6]eicosane)-cobalt(III)). At neutral pH, t
hese complexes are adsorbed as a trivalent cation up to 90%-100% of th
e cation exchange capacity of a clay. No difference is observed in the
maximum adsorption amount between the racemic and enantiomeric isomer
s. The basal spacings of the clay-chelate adducts are determined by th
e X-ray diffraction measurements of non-oriented powder samples: 14.3
angstrom for [Co(en)3]3+ montmorillonite, 16.5 angstrom for [Co(diNOsa
r)]3+ montmorillonite, and 16.9 angstrom for [Co(diAMsar)]3+ montmoril
lonite. The results imply that the chelates form a monolayer in the in
terlayer space. From the one-dimensional Fourier analyses of the diffr
action pattern of [Co(diNOsar)]3+ montmorillonite, the chelate is conc
luded to be adsorbed with its three-fold symmetry axis in parallel wit
h the layer surface. This is in contrast with the previous results of
(Ru(phen)3]2+ and [Ru(bpy)3]2+, which are adsorbed with their three-fo
ld symmetry axes perpendicular to the surface. The conclusion is consi
stent with the angular dependence of the infrared absorption spectrum
of the film of the adduct.