Thermal irreversibility study on the electrocyclic reaction of diaryl maleic anhydrides by density functional calculations

Photochromic materials are now anticipated as promising candidates for erasable memory media of the next generation because organic materials are easy to tailor. Density Functional calculations at the B3LYP/6-311+G(d,p)//HF/3-21G and partly at the B3LYP/6-311++G(3df,3pd)//B3LYP/6-31G(d) levels were carried out for thermal irreversibility study of the titled compounds, a kind of photochromic materials which undergo cyclization and cycloreversion reactions. Eighteen configurations were characterized for both the cis and the trans forms of three diarylethene-type compounds. Among them, six were transition states. The results from the relative energy barriers and from the normal coordinate analyses of the imaginary frequencies show that Woodward–Hoffman principle about disrotatory and conrotatory mechanisms is valid for the thermal irreversibility study on the compounds. The thermal irreversibility of changing phenyl to thiophenyl groups in stilbene, of introducing methyl groups on central carbons that were responsible for the electrocyclic reaction was discussed. The applicability of Irie’s rule was investigated.