One- and two-photon absorption properties of novel multi-branched molecules

Abstract

One-photon absorption (OPA) and two-photon absorption (TPA) properties of a class of novel multi-branched molecules have been investigated. These molecules exhibit strong one- and two-photon absorption and have comparatively large TPA cross sections. The one-photon absorption of compounds containing two different stilbene (or a stilbene and an azobenzene) derivatives offers an unprecedented combination of that of individual parts. On the basis of correct geometries, optimized by using the AM1 method, the TPA cross sections of molecules were examined. The peak TPA cross section values (δ_max) calculated with the ZINDO-SOS method are in the range 11.35–41.18 × 10⁻⁴⁸ cm⁴·s photon⁻¹. The δ_max value increases as the donor strength increases and the π-center has an important effect on the magnitude of the δ_max value. Compared with individual parts, the TPA cross sections of combinations of two different stilbene (or a stilbene and an azobenzene) derivatives exhibit a significant enhancement. Thus, another design strategy to maximize the TPA cross section is established.