Coordination of metal ions by indolic acids. Complexes of indole-3-carboxylic, indole-3-acetic, indole-3-β-acrylic, indole-N-acetic and indole-N-methyl-2-carboxylic acids with some divalent metal ions

Complexes of formula M(L)2·nH2O [M=Co or Ni; L=indole-3-carboxylic (I3CH), indole-3-acetic (I3AH), indole-N-acetic (INAH), indole-N-methyl-2-carboxylic (INMH) and M=Co or Ni and Cu, L=indole-3-β-acrylic acids (I3βH)] were pepared and characaterized by i.r. and electronic spectroscopy and by susceptibility measurements and e.s.r. at room and low temperature. The cobalt and nickel complexes exhibit a distorted octahedral coordination except the Co(I3C)2 complex for which a tetrahedral coordination was suggested. The Cu(I3β)2·H2O shows e.p.r. features that can be interpreted if the triplet state, S=1, depending on the temperature, is able to migrate through the crystal lattice of carboxylate dimers such as the copper(II) acetate monohydrate. © 1992 Chapman & Hall.