Spin-Vibronic Coupling Controls the Intersystem Crossing of Iodine-Substituted BODIPY Triplet Chromophores

0577471 - ÚOCHB 2025 RIV DE eng J - Journal Article
Doležel, Jiří - Poryvai, Anna - Slanina, Tomáš - Filgas, J. - Slavíček, P.
Spin-Vibronic Coupling Controls the Intersystem Crossing of Iodine-Substituted BODIPY Triplet Chromophores.
Chemistry - A European Journal. Roč. 30, č. 4 (2024), č. článku e202303154. ISSN 0947-6539. E-ISSN 1521-3765
R&D Projects: GA ČR(CZ) GJ19-20467Y
Institutional support: RVO:61388963
Keywords : BODIPYs * El-Sayed rules * intersystem crossing * spin-vibronic couplings * triplet chromophores
OECD category: Physical chemistry
Impact factor: 4.3, year: 2022
Method of publishing: Open access
https://doi.org/10.1002/chem.202303154

4,4-difluoro-4-borata-3a-azonia-4a-aza-s-indacene (BODIPY) dyes are extensively used in various applications of their triplet states, ranging from photoredox catalysis, through triplet sensitization to photodynamic therapy. However, the rational design of BODIPY triplet chromophores by ab initio modelling is limited by their strong interactions of spin, electronic and vibrational dynamics. In particular, spin-vibronic coupling is often overlooked when estimating intersystem crossing (ISC) rates. In this study, we developed a combined experimental and theoretical approach using spin-vibronic coupling to correctly describe ISC in BODIPY dyes. For this purpose, we examined seven π-extended BODIPY derivatives with iodine atoms in different positions. We found that the heavy-atom effect of iodine atoms is site-specific, causing high triplet yields in only some positions. This site-specific ISC was explainedby El-Sayed rules, so both the contribution and character of the molecular orbitals involved in the excitation must be considered when predicting the ISC rates. Overall, the rational design of BODIPY triplet chromophores requires using (i) the high-quality electronic structure theory, including both static and dynamical correlations, and (ii) the two-component wave function Hamiltonian, and rationalizing (iii) ISC based on the character of the molecular orbitals of heavy atoms involved in the excitation, expanding El-Sayed rules beyond their traditional applications.
Permanent Link: https://hdl.handle.net/11104/0346602