Photochromic properties calculation of diaryl maleic anhydride

Abstract In the calculation of the photochromic mechanism of (2,3-di(3-furyl)maleic anhydride, DFMA) ( as reported in Acta Phys. Sinica. 2021, 70(16): 163101), it was discovered that between the open-ring and closed-ring stable configurations, the potential energy curves of the electronic ground state (S 0 ) and the first excited state (S 1 ) exhibited an ‘X’ shape distribution along the reaction path. The conversion between open-ring and closed-ring occurs at the intersection of the potential energy curves, and a photoinduced ring-closing reaction accompanied by fluorescence was predicted, while a photoinduced ring-opening reaction was not. In this work, we apply the same method to investigate the mechanism of the photoinduced molecular switching process in the compounds of 2,3-di(3-thienyl)maleic anhydride(DTMA) and 2,3-di(3-pyrrolyl)maleic anhydride(DPMA). The transition state (TS) and minimum energy path (MEP) between the open-ring and closed-ring were determined by using the nudged elastic band (NEB) method. The potential energy curves of the lowest eight single excited states of DxMA(x = F, T, P) were computed based on the molecular configurations corresponding to the MEP curve (ground state S 0 ). Interestingly, only the first excited state (S 1 state) has a minimum value in the TS configuration among all eight excited states. That is, between the open-ring and closed-ring, the potential curves of S 0 and S 1 display an ‘X’ shape with a cross occurred at the TS configuration. The calculation of the S 1 ←S 0 resonance vibronic absorption spectrum of the open-ring/closed-ring state via molecular dynamics reveals that the transition intensity of the closed-ring state is 3 ∼ 5 times that of the open-ring state, which demonstrates that the efficiency of the closed-ring to the open-ring is higher.