The change of hydrogen position on π-conjugated bridge to affect NLO property of D(–NH2)-π(DHTPs)-A(–NO2) system

Abstract

The donor-π-conjugated bridge-acceptor (D-π-A) is a classical framework to design high-performance organic electro-optical materials. In this work, based on the π-conjugated dihydrotetraazapentacenes (DHTPs), four isomers (1–4) with D(–NH2)-π(DHTPs)-A(–NO2) framework are designed and characterized. The 2 and 3 originate from single-hydrogen migration of 1, and 4 derives from double-hydrogen migration of 1. Significantly, the change of hydrogen position on DHTPs bridge can affect their nonlinear optics (NLO) property. Compared with the first hyperpolarizability (βtot) (4.08 × 103a.u.) of 1, the 6.90 × 103-2.56 × 104 a.u. of 2–4 are enhanced. More interestingly, the 4 has largest βtot value of 2.56 × 104, which is approximately equal to the sum of 6.90 × 103 a.u. of 2 and 1.82 × 104 a.u. of 3. Furthermore, the change of hydrogen position on DHTPs brings some distinctive changes in their geometric structure, nucleus-independent chemical shifts (NICS) value, natural population analysis (NPA) charge, UV–vis absorption spectrum along with its other electronic property that might be beneficial to explore their structure–property relationships.