Photochromic dihetarylethenes. 9. Dithienylperfluorocyclopentenes: a quantum-chemical study

MNDO calculations of the open and cyclic forms of the molecules of three photochromic 1,2-di(3-thienyl)perfluorocyclopentene derivatives were carried out. Structural parameters as well as electronic and thermodynamic characteristics of the compounds studied were analyzed. The optimized geometric parameters of the open forms of the three molecules under study are in satisfactory agreement with the results of X-ray diffraction studies. Analysis of the effect of substituents on the electronic characteristics of the central fragment and on the composition of the frontier MOs suggests that it is more appropriate to use cyclic rather than open forms of the molecules for correlation analysis and for prediction of photochromism of dithienylperfluorocyclopentenes.