Synthesis and structure of a novel mixed-ligand electroluminescence-relevant complex of gallium(III) with 2-(2′-hydroxylphenyl)benzothiazole and acetate, and a theoretical investigation on effect of ancillary ligand on solid stacking structure, electroluminescent wavelength shift and other changes in photophysical properties compared to its conventional tris-chelate electroluminescence-relevant counterpart

Abstract

One novel mixed-ligand electroluminescence-relevant ML 2X-type Ga(III) complex (L: main ligand; X: ancillary ligand), [Ga(pbt) 2(Ac)] ( 1) (Hpbt = 2-(2′-hydroxylphenyl)benzothiazole, main ligand; HAc = acetic acid, ancillary ligand), has been prepared, structurally characterized and investigated theoretically. The reason for forming novel mixed-ligand electroluminescence-relevant ML 2X-type complex of 1, but not conventional tris-chelate electroluminescence-relevant ML 3-type complex ([Ga(pbt) 3]) is ascribed to the steric hindrance from bulky N,O-donor main ligand (pbt −). The effect of ancillary ligand (Ac −) on the supramolecular π–π stacking interactions, the electron transport ability and electroluminescent wavelength shift and other changes in photophysical properties of important optical transitions in crystalline 1 with respect to its tris-chelate electroluminescence-relevant counterpart [Ga(pbt) 3] have been analyzed in detail. The important electroluminescent/photoluminescent transition is only mainly related to the main ligands (pbt −) with π → π* ligand-to-ligand charge transfer (LLCT) transition nature based on the density functional theory (DFT) and time-dependent density functional theory (TDDFT) results.