Syntheses, Crystal Structures and Photophysical Properties of Dinuclear Copper(I) Complexes Bearing Diphenylphosphino-Substituted Benzimidazole Ligands

Three dinuclear copper(I) complexes (1, 2 and 3) of the form [(P N)Cu](2)(mu(2)-I)(2) have been designed and synthesized with 4-diphenylphosphino-benzimidazole (P N) derivatives. X-ray structural analysis shows that the complexes possess one rhombohedral Cu2I2 dimer that is coordinated with two P N ligands and exhibits a trans-configuration. At 290 K, the copper complexes exhibit similar broad and featureless emission bands with peak maxima (lambda(max)) at 585 nm, 565 nm and 586 nm, respectively. The temperature-dependent photophysical behaviors accompanied with the theory calculations demonstrate that 1 represents a thermally activated delayed fluorescence behavior at ambient temperature, whereas luminescence of 2 and 3 is phosphorescence. Moreover, the complexes (1-3) achieve high photoluminescence quantum yields of 36.9 %, 43.0 % and 34.0 % with relatively short emission decay times of 5.85 mu s, 7.99 mu s and 5.99 mu s, respectively. The solution-processed organic light-emitting diode based on 1 achieves a peak brightness of 3325 cd m(-2) and an EQE of 2.99 %.