Abstract
Herein, we present two novel cyclometalated Ir(III) complexes of dinuclear and trinuclear design, Ir-2(dppm)(3)(acac)(2) and Ir-3(dppm)(4)(acac)(3), respectively, where dppm is 4,6-di(4-tert-butylphenyl)pyrimidine ligand and acac is acetylacetonate ligand. In both cases, rac-diastereomers were isolated during the synthesis. The materials show intense phosphorescence of outstanding rates (k(r) = ...
Abstract
Herein, we present two novel cyclometalated Ir(III) complexes of dinuclear and trinuclear design, Ir-2(dppm)(3)(acac)(2) and Ir-3(dppm)(4)(acac)(3), respectively, where dppm is 4,6-di(4-tert-butylphenyl)pyrimidine ligand and acac is acetylacetonate ligand. In both cases, rac-diastereomers were isolated during the synthesis. The materials show intense phosphorescence of outstanding rates (k(r) = Phi(PL)/tau) with corresponding radiative decay times of only tau(r) = 1/k(r) = 0.36 mu s for dinuclear Ir-2(dppm)(3)(acac)(2) and still shorter tau(r) = 0.30 mu s for trinuclear Ir-3(dppm)(4)(acac)(3), as measured for doped polystyrene film samples under ambient temperature. Measured under cryogenic conditions, radiative decay times of the three T-1 substates (I, III, and III) and substate energy separations are tau(I) = 11.8 mu s, tau(II) = 7.1 mu s, tau(III) = 0.06 mu s, Delta E(II-I) = 7 cm(-1), and Delta E(III-I) = 175 cm(-1) for dinuclear Ir-2(dppm)(3)(acac)(2) and tau(I) = 3.1 mu s, tau(II) = 3.5 mu s, tau(III) = 0.03 mu s, Delta E(II-I) approximate to 1 cm(-1), and Delta E(III-I) = 180 cm(-1) for trinuclear Ir-3(dppm)(4)(acac)(3). The determined T-1 state ZFS values (Delta E(III-I)) are smaller compared to that of mononuclear analogue Ir(dppm)(2)(acac) (ZFS = 210(-1) cm). Theoretical analysis suggests that the high phosphorescence rates in multinuclear materials can be associated with the increased number of singlet states lending oscillator strength to the T-1 -> S-0 transition.
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