Modeling of graphene like structure by utilizing phenanthrocarbazole for tailoring the second-order nonlinear optical properties

Lower band gap with excellent intramolecular charge transfer plays a pivotal role towards developing the strong nonlinear optical (NLO) properties in a molecule. In the current investigation, we have designed a series of graphene like molecules with promising organic fragments that we have strategically adjoin the phenanthrocarbazole and tetracyanobuta-1,3-dienes (TCBD) fragment. Density functional theory (DFT) approach with CAM-B3LYPP/6-311+G(d,p) were performed to evaluate the nonlinear optical properties of designed derivative. The NLO characteristics were analysed the static polarizability (α₀), first order hyperpolarizabilities (β_tot) and band gap. The calculated results revealed that the designed molecules have better NLO response and highest β_tot were observed for molecule 10 (117871 au). Time dependent density functional based theories at the same level of theory were also performed to calculate the absorption spectra. The calculated results observed that there was a red shift trend with reduced band gap of designed derivative. Further, to substantiate our finding, we have also calculated density of states (DOS), molecular electrostatic potential (MESP) and transition density matrix (TDM) at the same level of theory. As a consequence the designed derivative shed light that the efficient TCBD group with graphene like molecular system and donor group can be utilized to design new molecular motif for NLO applications.