No abstract

No abstract

No abstract

No abstract

Herein, we report the effects of different electronwithdrawing groups (EWG) (−F) and electron-donating groups (EDG) (−OMe and −NH 2 ) on main ligands (ppy) and ancillary (acac) of [Ir(ppy) 2 (acac)] [ppy = 2-phenylpyridine; acac = acetylacetonato] using seven complexes by DFT and TDDFT calculations. We find that irrespective of the substituents, absorption of ppy-substituted complexes is blue-shifted, while for the acac-substituted complexes, it is red-shifted. The calculations also show that the substitution of EWGs causes an overall drop in the frontier molecular orbital energy levels; however, we observed a reverse effect for EDGs. To calculate the radiative rate k r , we considered the spin−orbit coupling matrix element (SOCME) (⟨T 1 |H SOC |S n ⟩) between S n (n = 1, 2, etc.) excited state and T 1 , transition dipole moment (μ(S n )), and the energy difference between excited singlet states S n and T 1 state (ΔE(S n − T 1 )). To compare the temperature-independent nonradiative process, we considered SOC between T 1 and S 0 (⟨T 1 |H SOC |S 0 ⟩) and the energy gap between optimized T 1 and S 0 states. Furthermore, to formulate the temperature-dependent nonradiative rate, we computed the activation barrier (E 1 ) for the metal-to-ligand state ( 3 MLCT) to a metal-centered state ( 3 MC) conversion. The emission peaks show that the changes of triplet state T 1 from 3 MLCT → 3 MC via transition states ( 3 TS) and 3 MLCT → 1 GS (GS = ground state) via the 3 MC/ 1 GS minimum energy crossing point are not much affected by the nature of substituents in the ancillary and the main ligand. The order of E 1 for the investigated complexes indicates that electron-donating substituents −OMe at both ppy and acac ligands can cause a decrease in nonradiative rate constants. Natural transition orbitals of the complexes show that they are mainly localized on the main ligand ppy and the Ir atoms and hardly on the ancillary ligand acac.