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

One novel mixed-ligand electroluminescence-relevant ML2X-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 ML2X-type complex of 1, but not conventional tris-chelate electroluminescence-relevant ML3-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 pi-pi 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 pi -> pi* ligand-to-ligand charge transfer (LLCT) transition nature based on the density functional theory (DFT) and time-dependent density functional theory (TDDFT) results. (C) 2010 Elsevier B.V. All rights reserved.