Theoretical investigation on the photoswitchable second-order nonlinear optical properties of a series of B(C6F5)2-coordinated dithienylethene derivatives

Abstract

The photoswitchable second-order nonlinear optical (NLO) properties of a series of B(C6F5)2-coordinated dithienylethene derivatives have been investigated by density functional theory (DFT) method. The calculations showed that static first hyperpolarizabilities (βtot) of ring-opening and ring-closed systems dramatically increased by introducing the appropriate substituents. Moreover, the calculated βtot values of ring-closed systems were larger than those of the corresponding ring-opening systems, it is mainly attributed to the forming of a larger π-conjugation in the ring-closed systems. The ring-closed form 5c owned the largest βtot values (7361.4 × 10−30 esu), which are 29.8 times larger than that of the corresponding ring-opening form 5o. Besides, to better describe the NLO behaviors of the studied dithienylethene derivatives, the absorption spectra and relative frontier molecular orbitals were calculated by time-dependent density functional theory (TDDFT) method. At last, we also demonstrated that the dispersions have barely influence on the frequency-dependent first hyperpolarizabilities (βtot (ω)) at the low-frequency region ω (0.000–0.030 a.u.). Thus, these theoretical calculations predicted the possible role of the studied systems as effective photoswitchable second-order NLO materials. We hope that this current work will pave the way for further theoretical and experimental design of efficient NLO materials.