Trinuclear Cyclometalated Iridium(III) Complex Exhibiting Intense Phosphorescence of an Unprecedented Rate

Marsel Z. Shafikov*, Andrey Zaytsev, Valery Kozhevnikov*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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 = Φ PL/τ) with corresponding radiative decay times of only τ r = 1/k r = 0.36 μs for dinuclear Ir 2(dppm) 3(acac) 2 and still shorter τ r = 0.30 μs 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 τ I = 11.8 μs, τ II = 7.1 μs, τ III = 0.06 μs, ΔE(II-I) = 7 cm -1, and ΔE(III-I) = 175 cm -1 for dinuclear Ir 2(dppm) 3(acac) 2 and τ I = 3.1 μs, τ II = 3.5 μs, τ III = 0.03 μs, ΔE(II-I) ≈ 1 cm -1, and ΔE(III-I) = 180 cm -1 for trinuclear Ir 3(dppm) 4(acac) 3. The determined T 1 state ZFS values (ΔE(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.

Original languageEnglish
Pages (from-to)1317-1327
Number of pages11
JournalInorganic Chemistry
Volume63
Issue number2
Early online date28 Dec 2023
DOIs
Publication statusPublished - 15 Jan 2024

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