High performance nonlinear optical materials with simple aromatic hydrocarbons

Design of novel functional materials with high-performance and high stability are of great importance in the field of nonlinear optics. In the present work, a new protocol is proposed for designing optical and nonlinear optical (NLO) functional material through proper interplay of functional moieties (in this work, benzene, naphthalene and azulene) by geometric arrangement within the classical D-pi-A paradigm. The pi-conjugation across the fused aromatic benzene, naphthalene and azulene, and the electronic structure retention of those functional moieties lead to the redistribution of pi-electron in azulene-based polar carbon chains and bring about large second order NLO responses. The charge transfer based electron transition at low energy field has a dominant contribution to the large static first hyperpolarizability (). The strong second order NLO responses under external fields, e.g., sum frequency generation and difference frequency generation, render these azulene-based molecules promising candidates for optoelectronic functional materials with high-performance in visible and near-infrared regions. The protocol of designing optical and nonlinear optical materials through manipulating the interactions among functional moieties is extendable to designing other optico-electronic functional materials.