Synthesis, Characterization, Photoluminescence, and Computational Studies of Monoorgano-Gallium and -Indium Complexes Containing Dianionic Tridentate ONE (E = O or S) Schiff Bases

The reactions of triorgano-gallium and -indium etherate with dianionic tridentate Schiff bases (2-hydroxy-N-salicylideneaniline (1a), 2-hydroxy-N-(2-hydroxy-3-methoxybenzylidene)aniline (1b), and 2-mercapto-N-salicylideneaniline (1c)) in benzene yielded complexes of the type [RM{O(2-C6H3R'-3)-CH=N(2-C6H4)E}] (where R = Me, Et; M = Ga, In; R' = H, OMe; E = O, S) in nearly quantitative yields. These complexes have been characterized by elemental analysis, IR, UV-vis, and NMR (H-1 and C-13{H-1}) spectroscopy. The molecular structures of [MeGa(-O(2-C6H4)-CH=N(2-C6H4)center dot O-)] (2a) and [MeGa(-O(2-C6H3OMe-3)center dot CH=N(2-C6H4)-O-)] (2b) were established by X-ray crystallography. Photoluminescence data of these complexes showed that the quantum yield was mainly affected by the substituent/groups attached to the phenyl moiety of the ligands rather than the metal atom. Density functional theory calculations have been used to assess all the possible structures and to evaluate the complexation energies corresponding to NeM{O(2-C6H4)-CH=N(2-C6H4)E}] (M = Ga, In; E = O, S) complexes.