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Electronic spectra and intersystem spin‐orbit coupling in 1,2‐ and 1,3‐squaraines
Author(s) -
Alberto Marta E.,
Mazzone Gloria,
Quartarolo Angelo D.,
Sousa Flavio Fortes Ramos,
Sicilia Emilia,
Russo Nino
Publication year - 2014
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.23725
Subject(s) - intersystem crossing , excited state , singlet fission , singlet state , density functional theory , chemistry , photochemistry , singlet oxygen , triplet state , spin–orbit interaction , computational chemistry , atomic physics , physics , oxygen , condensed matter physics , organic chemistry
The main photophysical properties of a series of recently synthetized 1,2‐ and 1,3‐squaraines, including absorption electronic spectra, singlet‐triplet energy gaps, and spin‐orbit matrix elements, have been investigated by means of density functional theory (DFT) and time‐dependent DFT approaches. A benchmark of three exchange‐correlation functionals has been performed in six different solvent environments. The investigated 1,2 squaraines have been found to possess two excited triplet states (T 1 and T 2 ) that lie below the energy of the excited singlet one (S 1 ). The radiationless intersystem spin crossing efficiency is thus enhanced in both the studied systems and both the transitions could contribute to the excited singlet oxygen production. Moreover, they have a singlet‐triplet energy gap higher than that required to generate the cytotoxic singlet oxygen species. According to our data, these compounds could be used in photodynamic therapy applications that do not require high tissue penetration. © 2014 Wiley Periodicals, Inc.