Bhattacharya Sayantan, Graf Arthur, Gomes Anna Karolyna M S, Chaudhri Nivedita, Chekulaev Dimitri, Brückner Christian, Cardozo Thiago M, Chauvet Adrien A P
Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, United Kingdom.
Instituto de Química (IQ), Federal University of Rio de Janeiro, Rio de Janeiro 21941-909, Brazil.
J Phys Chem A. 2022 Apr 28;126(16):2522-2531. doi: 10.1021/acs.jpca.2c01225. Epub 2022 Mar 29.
We demonstrate that β-oxo-substitution provides effective fine-tuning of both steady-state and transient electronic properties of octaalkyl-β-mono-oxochlorin and all isomers of the β,β'-dioxo-substituted chromophores. The addition of a carbonyl group increases the Q oscillator strength and red-shifts the absorption spectra. Each oxo-substitution results in a 2-fold increase in the singlet to triplet state intersystem crossing (ISC) rates, resulting in a 4-fold ISC rate increase for the dioxo-substituted chromophores. The effects of oxo-substitution on the ISC rate are thus additive. The progressive increase in the ISC rates correlates directly with the spin-vibronic channels provided by the C═O out-of-plane distortion modes, as evidenced by density functional theory (DFT) modeling. The triplet states, however, were not evenly affected by β-oxo-substitution, and reduction in the triplet lifetime seems to be influenced instead by the presence of NH tautomers in the dioxoisobacteriochlorins.
我们证明，β-氧代取代可有效微调八烷基-β-单氧代二氢卟吩以及β,β'-二氧代取代发色团的所有异构体的稳态和瞬态电子性质。羰基的添加增加了Q振子强度并使吸收光谱发生红移。每次氧代取代都会使单重态到三重态的系间窜越（ISC）速率增加2倍，从而使二氧代取代的发色团的ISC速率增加4倍。因此，氧代取代对ISC速率的影响是累加的。如密度泛函理论（DFT）建模所示，ISC速率的逐渐增加与C═O面外畸变模式提供的自旋-振动电子通道直接相关。然而，三重态并未受到β-氧代取代的均匀影响，三重态寿命的缩短似乎反而受到二氧代异菌绿素中NH互变异构体的影响。
