Sivanarayanan, Jibin ; Sebastian, Ebin ; Vinod, Kavya ; Würthner, Frank ; Hariharan, Mahesh (2022) Ultrafast Intersystem Crossing in Selenium-Annulated Perylene Bisimide Journal of Physical Chemistry C, 126 (31). pp. 13319-13326. ISSN 1932-7447
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Official URL: http://doi.org/10.1021/acs.jpcc.2c03847
Related URL: http://dx.doi.org/10.1021/acs.jpcc.2c03847
Abstract
An intersystem crossing (ISC), the non-radiative transition between two electronic states with different spin multiplicities, is ubiquitous and imperative in molecular photochemistry. The manifestation of a triplet manifold in π-conjugated chromophoric materials has a crucial role in enhancing the efficiency of photofunctional devices. Herein, we explore the triplet-state population in a series of chalcogen-annulated perylene bisimides (O-PBI, S-PBI, and Se-PBI), where the selenium-annulated PBI (Se-PBI) exhibits a near-quantitative triplet quantum yield ( = 94 ± 1%). Annulation of Se in the PBI core results in a drastic decrease in the fluorescence quantum yield ( = 1.5 ± 0.2%) compared to the bare PBI ( = 97.0 ± 1%), indicating the possibility of an efficient non-radiative decay pathway in the Se-PBI motif. Femtosecond and nanosecond transient absorption measurements unambiguously confirmed the ultrafast triplet population in Se-PBI with an ISC rate constant of = 2.39 × 1010 s–1 and the triplet-state decay to the ground state with a time constant of 3.78 μs. A theoretically calculated spin–orbit coupling constant (VSOC) of 122.4 cm–1 employing the SA-CASSCF/NEVPT2 method has rationalized the excited-state dynamics of Se-PBI. By virtue of the poor SOC between the singlet and triplet states, we observed a partial triplet population in S-PBI, whereas ISC is negligible in O-PBI. We demonstrate an increase in the spin–orbit coupling constant ( ≪ < ) and rate constant of ISC ( ≪ <) across the series of chalcogen-annulated PBIs (O-PBI, S-PBI, and Se-PBI). The heavier chalcogenide PBI (Se-PBI) thus adds to the array of potential organic photoactive materials for the design of efficient solar energy conversion devices.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Chemical Society. |
ID Code: | 127068 |
Deposited On: | 17 Oct 2022 05:19 |
Last Modified: | 17 Oct 2022 05:19 |
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