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

Abstract

Unraveling the photochemical behaviour of the green fluorescent protein chromophore has lately attracted widespread attention among scientists. 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 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. Three different 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.

Sulfated and Oxygenated Imidazoline Derivatives: Synthesis, Antioxidant Activity and Light‐Mediated Antibacterial Activity

“…Accordingly, the yields were determined at different temperatures and irradiation times. As a result, in Figure 2, it is plotted yields vs microwave conditions for compound 5 d where the maximum yield for this synthesis was 98 % at 130°C As it was already reported for compound 5 d, [23] Z and E isomers can be obtained for the benzylidene thioimidazolines. The preferred product has Z geometry, and the Z/E ratio can be modified by irradiation with light until the photostationary state is reached, at which point this ratio does not vary with the continuous irradiation.…”

“…We described the interaction of 5 d with light at the same wavelength in detail. [23] Our findings suggest that benzylidene derivatives have a Z!E photoisomerization process when irradiated at 366 nm. However, the opposite reaction (E!Z) is a thermal reversion process that can occur via a triplet state reached through an intersystem crossing between S 0 and T 1 surfaces (only thermal energy near room temperature is responsible for that reversion).…”

“…However, the opposite reaction (E!Z) is a thermal reversion process that can occur via a triplet state reached through an intersystem crossing between S 0 and T 1 surfaces (only thermal energy near room temperature is responsible for that reversion). [23] For this reason, we postulate herein that pro-oxidation processes are generated due to the Z!E isomerization reactions which are capable of converting triplet ChemMedChem Full Papers doi.org/10.1002/cmdc.202000048 oxygen ( 3 O 2 ) into singlet oxygen ( 1 O 2 ), one of the most reactive species of oxygen. Thus, the singlet oxygen can react with biomolecules to yield hydroperoxides through the following sequence of events [Eqs.…”

Photochemical anti–syn isomerization around the –N–N bond in heterocyclic imines

“…3,51 Many studies [52][53][54] have described these processes, wherein structural changes in the excited state allows the system to undergo photochemical isomerization via several pathways. [55][56][57] The NMR and DFT calculations were therefore focused on the analysis of structural changes in S1 that may plausibly be induced by the photochemical processes.…”

A study of the photochemical behaviour and relaxation mechanisms of anti–syn isomerisation around quinazolinone –N–N bonds

“…5,6 The isomerisation processes depend upon the structures of the photochemically sensitive compounds, but typically involve conjugated systems. 7,8 The excitation and the relaxation processes vary upon molecular arrangement in these systems. 9,10 The re-isomerisation process can proceed very rapidly, especially in molecules that possess a double bond between the bulky substituents, 11,12 although some other systems relax signicantly more slowly and require several orders of magnitude more time to reach their initial state.…”