Intersystem crossing via charge recombination in a perylene–naphthalimide compact electron donor/acceptor dyad. Issue 24 (29th May 2020)

• Record Type: Journal Article
• Authors: Imran, Muhammad; El-Zohry, Ahmed M.; Matt, Clemens; Taddei, Maria; Doria, Sandra; Bussotti, Laura; Foggi, Paolo; Zhao, Jianzhang; Di Donato, Mariangela; Mohammed, Omar F.; Weber, Stefan
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 24(2020)
• Page Start: 8305
• Page End: 8319
• Publication Date: 2020-05-29
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0tc00017e
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Efficient triplet state production (singlet oxygen quantum yield: 80%) by SOCT-ISC was observed for a perylene–naphthalimide compact electron donor/acceptor dyad. Abstract : In order to study the relationship between the molecular structures of compact electron donor/acceptor dyads and the spin–orbit charge transfer intersystem crossing (SOCT-ISC) efficiency, we prepared a perylene (Pery)–naphthalimide (NI) dyad, in which the Pery unit is the electron donor and the NI unit is the electron acceptor, where the two units adopt an almost orthogonal geometry. The photophysical properties of the dyad were studied with steady state and femtosecond/nanosecond transient absorption (fs TA and ns TA) spectroscopies, time resolved electron paramagnetic resonance (TREPR) spectroscopy and DFT computations. A very weak charge transfer (CT) absorption band was observed, but the fluorescence of the Pery unit is strongly quenched. Upon selective excitation into the NI unit, the fast intramolecular CS process (10 ps) occurs, followed by ISC and only the 3 Pery* state is observed; whereas upon selective photoexcitation into the perylene unit, an ultrafast charge separation (0.66 ps) is observed, followed by SOCT-ISC (8 ns) to populate the 3 Pery* state. Moreover, the perylene radical cation is also observed on the ns timescale, presumably formed by intermolecular charge transfer. The lifetime of the 3 Pery triplet state was determined to be τ T = 214 μs with ns TA spectroscopy. The singlet oxygen quantum yield was measured as Φ Δ = 80%, although the potential energy curve of the torsion between the donor and acceptor is shallow. The SOCT-ISC mechanism was confirmed by TREPR spectroscopy. The dyad was used as a triplet photosensitizer for the generation of delayed fluorescence (luminescence lifetime τ DF = 57.3 μs).