Structural characterization, electronic and luminescent properties of copper(I) complexes with different temperatures and their application to light-emitting diodes

Abstract

Three Cu(I) complexes, [Cu(dppb)(bbim)]BF4(1), [Cu(DPEphos)(bbim)]BF4 (2) and [Cu (Xantphos)(bbim)]BF4(3) (dppb =1, 2-bis(diphenylphosphino)benzene, DPEphos=bis(2-diphenyl phosphinophenyl)ether, Xantphos=9, 9-dimethyl-bis(diphenylphosphino)xanthenes, bbim = bisbenzimidazole), have been synthesized and characterized by IR, 1H NMR, 31P NMR, TG, XRD elemental analysis and X-ray crystal structure analysis. The structural analysis indicates that the increases in the temperature from 100 K to 300 K result in the change of bond lengths, bond angles and the weak interactions. Theoretical calculations demonstrate that the HOMO → LUMO energy gap and Mülliken atomic charges are increased or shorten by increasing temperature from 100 K to 300 K, in according with the change of bond lengths and angles, while the composition of HOMO and LUMO orbitals are nearly unchanged at different temperatures. Meanwhile, the solid-state luminescent properties of these copper(I) complexes at 100 K, 200 K and 300 K also exhibit that the change of temperature leads to the variation of the Kr, Knr, τ, Фem and λmax, having a certain degree of consistency with the related calculation results. In these complexes, the maximum phosphorescent lifetime and quantum yield are up to 309 μs and 23% at 300 K, respectively. Moreover, to estimate potential application of copper(I) complexes for LED, monochromatic and white LED have been fabricated, respectively, showing reasonable electroluminescence with the maximum external quantum efficiency 3.95% and 5.31%.