Phosphine-Disubstituted Gallium and Indium Compounds as Chelators for Transition Metals: Synthesis and Linker-Dependent Photophysical Properties

A new diphosphine-substituted Ga-based ligand, [(L)Ga(CH2PPh2)2] (1) was prepared as a potential chelator for transition metals complexes. The data indicate that 1 exhibits higher Lewis basicity and donor strength than conventional organic diphosphines due to the presence of the Ga center, which enhances its electronic properties. This ligand demonstrates efficient coordination behavior toward various metal centers as Ru(II), Ir(III), Ni(0), Pt(II), or Cu(I), forming stable bimetallic complexes in various coordination modes. The photophysical study of these complexes revealed the deep-blue emission of 1·CuX complexes with lifetimes in the μs range and quantum yield up to 0.12. The impact of the (pseudo)halogen ligand X (X = Cl, Br, I or SCN) and the metal linker in the ligand framework [(L)M(CH2PPh2)2] (M = Ga vs In) on the photophysical properties are discussed.