Adsorption and Spectroscopic Studies on the Interactions of Cobalt(III) Chelates with Clays

Masami Kaneyoshi1, 4, Akihiko Yamagishi2, Masahiro Tanaguchi2 and Akiko Aramata3
1 Department of Chemistry, College of Arts and Sciences, The University of Tokyo Komaba, Meguro-ku, Tokyo 153, Japan
2 Department of Polymer Sciences, Faculty of Sciences Hokkaido University, Sapporo 060, Japan
3 Catalysis Research Center, Hokkaido University Sapporo 060, Japan
4 Present address: Laboratory of Magnetic Materials, Shin-Etsu Co. Ltd., Takefu 915, Japan.

Abstract: The interactions of the following three kinds of racemic and enantiomeric cobalt(III) chelates with montmorillonite and saponite are studied: [Co(en)3]3+ (en = ethylenediamine), [Co(diNOsar)]3+ (diNOsar = (1,8-dinitro-3,6,10,13,16,19-hexaazabicyclo[6,6,6]-eicosane)cobalt(III)) and [Co(diAMsar)]3+ (diAMsar = (1,8-diamino-3,6,10,13,16,19-hexaazabicyclo-[6,6,6]eicosane)-cobalt(III)). At neutral pH, these complexes are adsorbed as a trivalent cation up to 90%–100% of the cation exchange capacity of a clay. No difference is observed in the maximum adsorption amount between the racemic and enantiomeric isomers. The basal spacings of the clay-chelate adducts are determined by the X-ray diffraction measurements of non-oriented powder samples: 14.3 Å for [Co(en)3]3+ montmorillonite, 16.5 Å for [Co(diNOsar)]3+ montmorillonite, and 16.9 Å for [Co(diAMsar)]3+ montmorillonite. The results imply that the chelates form a monolayer in the interlayer space. From the one-dimensional Fourier analyses of the diffraction pattern of [Co(diNOsar)]3+ montmorillonite, the chelate is concluded to be adsorbed with its three-fold symmetry axis in parallel with 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-fold symmetry axes perpendicular to the surface. The conclusion is consistent with the angular dependence of the infrared absorption spectrum of the film of the adduct.

Key Words: Clay-metal chelate interactions

Clays and Clay Minerals; February 1993 v. 41; no. 1; p. 1-6; DOI: 10.1346/CCMN.1993.0410101
© 1993, The Clay Minerals Society
Clay Minerals Society (www.clays.org)