Induced distant cotton effects in mixed Cu(II) complexes of amino and hydroxy acids and heterocyclic ligands
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Mixed 1:1:1 complexes of proline or aspartic acid with Cu(II) and 9:10-phenanthroline (phen) or 2,2'bipyridine (bipy) show induced Cotton effects in the aromatic region. The effect is ascribed to interactionsbetween the charge transfer transitions from the amino acid and the longitudinal π-π* transitions of the aromaticligand. There is not such induced optical activity in the mixed glutamate or valinate complexeswith Cu(II) andphen, and the bahavior of the prolinates and aspartates is explainablein terms of the arrangement of the ligands around the metal ion. The mixed 1:1:1 complex of L-malic acid and phen with Cu(II) also shows inducedCotton effectsin the aromatic region, but here in addition to the usual two positive aromatic band there is a veri weak negative band (at ca.315 nm) associated with a short axis polarized π-π* transition.