Mononuclear Aliii, Gaiii and Iniii, and heterodinuclear GaiiiMii (M = Zn, Cu, Ni, Co) complexes of a tetraiminodiphenol macrocyclic ligand

Abstract

Mononuclear aluminium(III), gallium(III) and indium(III) complexes [M^III(LH₂)(H₂O)Cl](ClO₄)₂·nH₂O (1–3) of the tetraiminodiphenolate 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 heterodinuclear complexes [Ga^IIIM^IIL(μ-OAc)(OAc)(H₂O)][ClO₄] (M = Co, 4; Ni, 5) and [Ga^IIIM^IIL(μ-OAc)(OAc)][ClO₄]·2H₂O (M = Cu, 6; Zn, 7). The presence of the core unit [Ga^IIIM^IIL(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. Spectrofluorimetric titrations of 2 with Zn(OAc)₂·2H₂O and Cu(OAc)₂·H₂O in acetonitrile have shown that the formation of a 1 ∶ 1 Ga^IIIZn^II complex occurs with the growth of luminescence intensity, while the formation of a Ga^IIICu^II complex leads to the complete quenching of luminescence. Complexes 1–7 have been further characterized by their proton NMR spectra.