Indium Coordination Compounds Derived from Amino Amides

Abstract

We report the synthesis of eight indium coordination compounds derived from amino amides 1-8 and InCl 3 . Crystallographic and NMR studies revealed the unusual chelation coordination of the metal ion to the amine and carbonyl groups of the ligands. However, vibrational studies evidenced the presence of formation-breaking equilibria of the C=O!In 3 + coordination bond. Thus, as chelate structures predominate in methanol solutions, In 3 + compounds with open structures prevail in aqueous solutions. Moreover, the Raman spectroscopy and crystallography studies of 2 c and 6 c corroborated that the substitution of a chlorine ion by a methanol molecule in these coordination compounds is feasible and that the interchange equilibrium [HL]InCl 4 + MeOH⇄[L][MeOH]InCl 3 + HCl is present in methanolic solutions. UV spectroscopy proves that the [HL]InCl 4 compounds predominates in methanol solutions. However, fluorescence spectroscopy shows the presence of significant quantities of [L][MeOH]InCl 3 that reduce the intensity of the signals. The formation-breaking and interchange equilibria could facilitate the biological interchange of In 3 + using coordination compounds 1 c-8 c.