Imran, Muhammad and Kurganskii, Ivan and Maity, Partha and Yu, Fabiao and Zhao, Jianzhang and Gurzadyan, Gagik G. and Dick, Bernhard and Mohammed, Omar F. and Fedin, Matvey (2024) Origin of Intersystem Crossing in Red-Light Absorbing Bodipy Derivatives: Time-Resolved Transient Optical and Electron Paramagnetic Resonance Spectral Studies with Twisted and Planar Compounds. JOURNAL OF PHYSICAL CHEMISTRY B, 128 (40). pp. 9859-9872. ISSN 1520-6106, 1520-5207
Full text not available from this repository. (Request a copy)Abstract
We studied the intersystem crossing (ISC) property of red-light absorbing heavy atom-free dihydronaphtho[b]-fused Bodipy derivatives (with phenyl group attached at the lower rim via ethylene bridge, taking constrained geometry, i.e., BDP-1 and the half-oxidized product BDP-2) and dispiroflourene[b]-fused Bodipy (BDP-3) that have a twisted pi-conjugated framework. BDP-1 and BDP-3 show strong and sharp absorption bands (i.e., epsilon = 2.0 x 10(5) M-1 cm(-1) at 639 nm, fwhm similar to 491 cm(-1) for BDP-3). BDP-1 is significantly twisted (phi = 21.6 degrees), while upon mono-oxidation, BDP-2 becomes nearly planar on the oxidized side (phi = 3.5 degrees). Interestingly, BDP-2 showed efficient ISC (triplet state quantum yield, Phi(T) = 40%) due to S-1/T-2 state energy matching. Long-lived triplet excited state was observed (tau(T) = 212 mu s in solution and 2.4 ms in polymer matrix), and ISC takes 4.0 ns. Differently, twisted BDP-1 gives weak ISC only 5%, ISC takes 7.7 ns, and the triplet state is populated only with addition of ethyl iodide. Time-resolved electron paramagnetic resonance spectra of BDP-1 revealed the coexistence of two triplet states, with drastically different zero-field splitting D parameters of -2047 MHz and -1370 MHz, respectively, along with varying sublevel population ratios. We demonstrate that the ISC is not necessarily enhanced by torsion of the pi-conjugation framework; instead, S-1/T-n state energy matching is more efficient to induce ISC even in compounds that have planar molecular structures.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | TRIPLET-TRIPLET ANNIHILATION; PHOTON UP-CONVERSION; EXCITED-STATE; PHOTOPHYSICAL PROPERTIES; PHOTOSENSITIZERS; COMPLEXES; SINGLET; DYES; EPR; SPECTROSCOPY; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 20 Aug 2025 10:27 |
| Last Modified: | 20 Aug 2025 10:27 |
| URI: | https://pred.uni-regensburg.de/id/eprint/65498 |
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