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A comparative multi‐reference configuration interaction study of the low‐lying states of two thione isomers of thiophenol
Author(s) -
Lima Filipe Belarmino de,
Pereira Rodrigues Gessenildo,
Lucena Júnior Juracy Regis,
Ventura Elizete,
Fausto Rui,
Reva Igor,
Monte Silmar Andrade
Publication year - 2020
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.26263
Subject(s) - configuration interaction , wave function , thiophenol , excited state , chemistry , full configuration interaction , atomic physics , complete active space , computational chemistry , physics , basis set , density functional theory , medicinal chemistry
Multi‐reference configuration interaction, MR‐CI (including extensivity corrections, named +Q), calculations were performed on the S 0 –S 3 states of cyclohexa‐2,4‐diene‐1‐thione (thione 24 ) and cyclohexa‐2,5‐diene‐1‐thione (thione 25 ), which are thione isomers of thiophenol. Several types of uncontracted MR‐CIS and MR‐CISD wavefunctions were employed, comprising MR‐CI expansions as large as ~365 × 10 6 configuration state functions. The nature of the studied excited states was characterized. Vertical excitation energies (Δ E ) and oscillator strengths ( f ) were computed. The most intense transitions (S 0 → S 2 for 24 and S 0 → S 3 for 25 ) did not change with the wavefunction, although a variation as large as ~1 eV was obtained for the S 3 state of 24 , at the highest (MR‐CI+Q) level. On the other hand, Δ E changed at most by ~0.56 eV for 25 as the wavefunction changes, at the same level. The S 1 state of both thiones was found to have n π * character and is in the visible region. For 24 , S 2 and S 3 are ππ * and n π * states, respectively, while for 25 the reverse order is obtained. S 2 and S 3 are in the range ~3.5 to 5.2 eV, again at the highest level. It is the first time that the excited states of the title molecules are studied. The computed results agree with the experimental onset of photoreactions of thiones 24 and 25 found by Reva et al ( Phys. Chem. Chem. Phys. , 2015 , 17 , 4888).