Mononuclear Al, Ga and In, and hetero-dinuclear Ga M (M = Zn, Cu, Ni, Co) complexes of a tetra-imino-di-phenol macrocyclic ligand

Mononuclear aluminium(III), gallium(III) and indium(III) complexes [MIII(LH2)(H2O)Cl](ClO4)2.nH2O (1-3) of the tetra-imino-di-phenolate macrocyclic ligand L2- have been synthesized. The two uncoordinated imine nitrogens of these compounds are protonated and hydrogen bonded to the metal-bound phenolate oxygens to stabilize them against hydrolytic cleavage. The gallium(III) compound, 2, forms the hetero-dinuclear complexes [GaIIIMIIL(μ-OAc)(OAc)(H2O)][ClO4] (M = Co, 4; Ni, 5) and [GaIIIMIIL(μ-OAc)(OAc)][ClO4].2H2O (M = Cu, 6; Zn, 7). The presence of the core unit [GaIIIMIIL(μ-OAc)(OAc)]+ in all the compounds has been ascertained by ESI-MS measurements. Complexes 1-3 show luminescence at room temperature between 505 and 490 nm. Spectro-fluorimetric titrations of 2 with Zn(OAc)2.2H2O and Cu(OAc)2.H2O in acetonitrile have shown that the formation of a 1:1 GaIIIZnII complex occurs with the growth of luminescence intensity, while the formation of a GaIIICuII complex leads to the complete quenching of luminescence. Complexes 1-7 have been further characterized by their proton NMR spectra. (authors)