Synthesis, Structures, Photoluminescent Behaviors, and DFT Studies of Novel Aluminum Complexes Containing Phenoxybenzotriazole Derivatives

Treatment of AlMe3 with 2 equiv of 2-(2H-benzo[d][1,2,3]triazol-2-yl)-4.6-di-tert-pentylphenol (Lig(1)H) or 2-tert-butyl-6-(5-chloro-2H-benzo[d][1,2,3] triazol-2-yl)-4-methylphenol (Lig(2)H) and subsequent addition of ROH afford monomeric and heteroleptic (OR)AlL2 complexes [R = C6H5, L = Lig(1), 1; R = p-C6H4Ph, L = Lig(1), 2; R = C6H5, L = Lig(2), 3; R = p-C6H4Ph, L = Lig(2), 4]. The simple reaction between a quantitative amount of water and compound 1 gave the novel dimeric aluminum complex 5 bridged by in oxygen atom. The crystal structures of 1, 3, and 5 determined from X-ray diffraction studies reveal pentacoordination geometry around the Al center with the preference for the slightly distorted trigonal-bipyramidal geometry. Monomeric complexes 1-4 showed emissions of the blue region (475 nm) with broad emission areas (half-width of peak = 150 nm) in the emission spectrum with high quantum yield. Dimeric aluminum complex 5 with enhanced thermal stability has a similar absorption and emission pattern to complexes 1 and 2. as predicted by DFT calculations. The DFT calculations suggested that the HOMO and LUMO orbitals are localized on the phenoxy group and benzotriazole group of the ligand and the effect of the phenoxide ligand is negligible.