Activating Organic Phosphorescence via Heavy Metal-π Interaction Induced Intersystem Crossing.

Sun, Meng-Jia; Anhalt, Olga; Sárosi, Menyhárt B; Stolte, Matthias; Würthner, Frank · Adv Mater · 2022

basic_science · Level V

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Abstract

Heavy-atom-containing clusters, nanocrystals, and other semiconductors can sensitize the triplet states of their surface-bonded chromophores, but the energy loss, such as nonradiative deactivation, often prevents the synergistic light emission in their solid-state coassemblies. Cocrystallization allows new combinations of molecules with complementary properties for achieving functionalities not available in single components. Here, the cocrystal formation that employs platinum(II) acetylacetonate (Pt(acac)<sub>2</sub> ) as a triplet sensitizer and electron-deficient 1,4,5,8-naphthalene diimides (NDIs) as organic phosphors is reported. The hybrid cocrystals exhibit room-temperature phosphorescence confined in the low-lying, long-lived triplet state of NDIs with photoluminescence (PL) quantum yield (Φ<sub>PL</sub> ) exceeding 25% and a phosphorescence lifetime (τ<sub>Ph</sub> ) of 156 µs. This remarkable PL property benefits from the noncovalent electronic and spin-orbital coupling between the constituents.