An experimental and theoretical study of the photoisomerization and thermal reversion on 5-arylmethylene-2-thioxoimidazolidin-4-one

JULIETA PEPINO; MAXI A. BURGOS PACI; WALTER PELAEZ; GUSTAVO A ARGÜELLO

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 latelyattracted widespread attention among scientists. In this paper we present the study of the photochemicalisomerization Z - E and the back reaction of the chromophore analog, 5-arylmethylene-2- thioxoimidazolidin- 4-one. Experimental results are supported with ab initio calculations 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 S0 respectively. Threedifferent mechanisms were analyzed for thermal reversion, concluding that the preferred channel involves an intersystem crossing between the S0 and T1 states with the formation of a biradical.