Phosphorescent Ir(III) complexes bearing double benzyldiphenylphosphine cyclometalates; strategic synthesis, fundamental and integration for white OLED fabrication

A new Ir(III) complex [Ir(bdp)(2)(OAc)] (1) was prepared by the treatment of IrCl3(tht) 3 with approx. two equivalent of benzyldiphenylphosphine in refluxing decalin solution, bdpH benzyldiphenylphosphine and tht tetrahydrothiophene. Complex 1 proves to be a versatile precursor, which could further react with various triazolate chelates such as 5-pyridyl-3-trifluoromethyl-1,2,4triazole (fptzH), 3-tert-butyl-5-(2-pyridyl)-1,2,4-triazole (bptzH), 5-(1-isoquinolyl)-3-tert-butyl-1,2,4triazole (iqbtzH) and 5-(1-phenanthridinyl)-3-tert-butyl-1,2,4-triazole (pbtzH) to afford the emissive complexes [Ir(bdp)(2)(fptz)] (2), [Ir(bdp) 2(bptz)] (3), [Ir(bdp)(2)(iqbtz)] (4), and [Ir(bdp)(2)(phbtz)] (5), respectively. Single crystal X-ray diffraction studies of 1 and 5 revealed a distorted octahedral Ir(III) metal core, both possess two mutually orthogonal bdp cyclometalates, and the respective PPh(2) donors reside at the cis-orientation. Formation of complexes 2-5 can be envisioned as simple replacement of acetate with the incoming N-heterocyclic triazolate chelates. As for photophysical properties, the structural variation leads to salient difference in emission features among complexes 2-5. Combining theoretical approaches, the results are rationalized by the contribution from the degree of ligand p-conjugation, together with the occurrence of ligand-to-ligand charge transfer (LLCT) and intraligand pp* transition in the lowest lying excited state. The orange-red and white light-emitting OLEDs were then fabricated using 5 as dopant, for which the respective devices gave peak efficiencies of 13.6% photons/electron, 33.3 cd A(-1), 29.8 lm/W and with CIE(x,y) = 0.530, 0.467 at 100 cd m(-2), and peak efficiencies of 13.0% photons/electron, 28.0 cd A(-1), 22.8 lm/W, and with CIE(x,y) = 0.356, 0.348 at 1000 cd m(-2)