An Experimental and Theoretical study of the Photoisomerizacion and Thermal Reversion of 5-arylmethylene-2-thioxoimidazolidin-4-one

PEPINO, A. J.; BURGOS, M.; PELÁEZ, W. J.; ARGÜELLO, G. A.

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: Cambridge; Año: 2015 vol. 17 p. 12927 - 12934

1463-9076

Unraveling the photochemical behaviour of the green fluorescent protein chromophore has lately attracted widespread attention amongscientists. In this paper we present the study of the photochemical isomerization Z-E and the back reaction of the chromophore analog, 5-arylmethylene-2- thioxoimidazolidin-4-one. Experimental results are supported withab initiocalculations at the DFT, (B3LYP/6-31+g(d,p)), TD-DFT (B3LYP/ 6-311++g(3df,3pd)) and CASSCF levels. A first excitation to the S2 state, where the isomerization occurs, is proposed followed by two conical intersections to S1 and S0respectively. Three different mechanisms were analyzed for thermal reversion, concluding that the preferred channel involves an intersystem crossing between the S0and T1 states with the formation of a biradical.