DFT study of effect of substituents on second-order NLO response of novel BODIPY dyes

Abstract

Based on molecular structural design of boron-dipyrromethene (BODIPY), nine BODIPY derivatives decorated with vinyl, phenyl, dimethylamino, nitro and aldehyde group substituents, respectively, have been systematically investigated by the density function theory (DFT) method. The purposes of this paper are to study the effect of various substituents and their positions on geometric structures, electronic structures and second-order nonlinear optical (NLO) properties. In addition, the effects of polarizable environment and electric fields on the first hyperpolarizabilities (βtot) values have been investigated. It is found that the incorporation of strong electron-donating dimethylamino could induce a significant enhancement of the βtot values, and the βtot values of the bilateral α-position substitution are much larger with respect to the unilateral α-position substitution, because those substituents are able to expend the BODIPYs’ delocalized π-electron system to different extents. Time-dependent DFT results suggest that the increasement of the βtot values is related to the intramolecular charge transfer from substituents to BODIPY core. Thus, forming a D-π-A model is favorable for increasing the βtot values, where BODIPY was used as electron accepting. Hence, we hope this work will be beneficial to further investigating versatile and novel NLO materials.