Salazar Edison, Reinink Suzanne, Faraji Shirin
Theoretical Chemistry, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Phys Chem Chem Phys. 2022 May 18;24(19):11592-11602. doi: 10.1039/d2cp00550f.
Dithienylethene (DTE) molecular photoswitches have shown to be excellent candidates in the design of efficient optoelectronic devices, due to their high photoisomerization quantum yield (QY), for which symmetry is suggested to play a crucial role. Here, we present a theoretical study on the photochemistry of a non-symmetric dithienylethene photoswitch, with a special emphasis on the effect of asymmetric substitution on the photocyclization and photoreversion mechanisms. We used the Spin-Flip Time Dependent Density Functional Theory (SF-TDDFT) method to locate and characterize the main structures (conical intersections and minima) of the ground state and the first two excited states, S and S, along the ring-opening/closure reaction coordinate of the photocyclization and photoreversion processes, and to identify the important coordinates governing the radiationless decay pathways. Our results suggest that while the main features that characterize the photoisomerization of symmetric DTEs are also present for the photoisomerization of the non-symmetric DTE, the lower energy barrier on S along the cycloreversion reaction speaks in favor of a more efficient and therefore a higher cycloreversion QY for the non-symmetric DTEs, making them a better candidate for molecular optoelectronic devices than their symmetric counterparts.
二噻吩乙烯（DTE）分子光开关由于其高光异构化量子产率（QY），已被证明是高效光电器件设计中的优秀候选者，其中对称性被认为起着关键作用。在此，我们对一种非对称二噻吩乙烯光开关的光化学进行了理论研究，特别强调了不对称取代对光环化和光回复机制的影响。我们使用自旋翻转含时密度泛函理论（SF-TDDFT）方法，沿着光环化和光回复过程的开环/闭环反应坐标，定位并表征基态以及前两个激发态S₁和S₂的主要结构（锥形交叉点和极小值），并确定控制无辐射衰变途径的重要坐标。我们的结果表明，虽然对称DTE光异构化的主要特征在非对称DTE的光异构化中也存在，但沿着环化反应S₁上较低的能垒表明非对称DTE具有更高效的环化过程，因此环化量子产率更高，这使得它们比对称的DTE更适合作为分子光电器件的候选材料。
