Study of ultrafast nonlinear optical response and transient dynamics of pyrene derivatives with intramolecular charge transfer characteristics

Abstract

Two pyrene derivatives 1906 and 1936 with typical charge transfer characteristics were designed and synthesized to study the influence of intramolecular charge transfer (ICT) on the ultrafast nonlinear optical (NLO) absorption. Frontier molecular orbital distribution and hole-electron analysis show that compound 1906 has stronger ICT characteristics than 1936 by introducing the halogen effect. Intense ESA signals in the green region of these pyrene derivatives were observed in the transient absorption spectrum (TAS). The excited state dynamics clearly show singlet-based electronic transitions and relaxation processes. Femtosecond Z-scan experiment at 480 nm indicates the ultrafast NLO absorption performance of these pyrene derivatives can be significantly improved by enhancing the ICT characteristics. The photophysical mechanism is one-photon absorption (OPA) induced excited-state absorption (ESA). As the input intensity is 46.8 GW cm−2, the effective NLO absorption coefficient of 1906 is 7.6 × 10−13 W m−1 which is 6.3 times that of 1936. Our results indicate that these pyrene derivatives are promising potential candidates for ultrafast laser protection applications.