Density Functional Theory Predictions of the Nonlinear Optical (NLO) Properties in Triphenylamine based α-Cyanocinnamic Acid Compounds: Effect of Fluorine on NLO Response

Abstract

In this study, the energy gaps, second-order nonlinear optical (NLO) properties and dipole polarizabilities of triphenylamine based α-cyanocinnamic acid acetylene derivatives have been investigated via using time-dependent density functional response theory. These compounds were designed theoretically by fluorine (F) atom substitution at different positions of phenyl ring end of the α-cyanocinnamic acid segment. The results have indicated that the systems substituted by fluorine show remarkable NLO second-order response, especially D4 system with computed static second-order polarizability (βtot) of 70537.95 (a.u). Hence, these materials have the likelihood to be an excellent second-order nonlinear optical (NLO) materials. The βtot value suggests that along the x-axis the charge transfer (CT) from triphenylamine to α-cyanocinnamic acid (D-A) plays a key role in NLO response; whereas α-cyanocinnamic acid acts as an acceptor (A) and triphenylamine acts as a donor (D) in all the studied systems. Incorporation of an electron acceptor (F) at the phenyl ring end of the α-cyanocinnamic acid segment increases the computed βtot values. The present investigation therefore provides an important insight into the remarkably greater NLO properties of α-cyanocinnamic acid and triphenylamine attached via acetylene.