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 [H L ]InCl 4 +MeOH⇄[ L ][MeOH]InCl 3 +HCl is present in methanolic solutions. UV spectroscopy proves that the [H L ]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 .