A DFT study on tautomerism of selenorhodanine and its substituted derivatives

Abstract

Rhodanine (2-thioxo-4-thiazolidinone) is a compound with a strong biological activity. It is also a ligand widely used in coordination chemistry. Replacing its exocyclic sulfur atom with selenium generates so called selenorhodanine. Selenorhodanine can exist in several tautomeric forms. Thus, the main aim of our research is to study the tautomeric equilibria in un substitued and substituted selenorhodanines. Substitution of nitrogen as well as the carbon atoms of the selenorhodanine ring with several substituents is considered. In order to achieve this goal we performed DFT calculations at the B3LYP/6-311++G∗∗ level for five theoretically possible tautomers of selenorhodanine. The results of performed calculations show that the most stable structure of selenorhodanine is similar to the equilibrium structures of rhodanine and thiazolidine-2,4-dione. We also calculated tautomeric equilibria for substituted selenorhodanines at the same level of theory and analyzed how the formation of intramolecular hydrogen bonds between some substituents and selenorhodanine ring can influence tautomeric equilibria in the compounds of interest.