Structural parameter-modulated nonlinear optical amplitude of acceptor-π-D-π-donor-configured pyrene derivatives: a DFT approach

Abstract

In the present study, organic pyrene-based derivatives were selected for NLO investigation. The reference compound named methyl (E)-2-cyano-3-(5-(pyren-1-yl)thiophen-2-yl)-3-acrylate (MCPTR) was taken for the design of its derivatives, abbreviated fromMCPTD1toMCPTD8compounds. The nonlinear optical (NLO) properties, frontier molecular orbitals (FMOs), natural bonding orbital (NBO), and UV-vis analyses of molecules (MCPTR-MCPTD8) were executed by M06 level with 6-31G(d,p) basis set. The UV-vis investigation showed that all designed compounds exhibited a redshift, and the maximum wavelength was studied inMCPTD7(832.330 nm). The HOMO-LUMO band gaps ofMCPTD1-MCPTD8were found to be smaller as compared to those ofMCPTR(3.210 eV). The global reactivity information was correlated with band gap values;MCPTD7, having a lower band gap, exhibited smaller hardness values (0.0321Eh) with larger softness values (15.5763Eh). The natural bond orbital analysis (NBO) helped to elucidate the hyper conjugative interactions, along with the stability and electron-transfer process. The dipole moment (μ), average polarizability 〈α〉, first hyperpolarizability (βvec) and second hyperpolarizability 〈γ〉 were computed forMCPTR-MCPTD8. Consequently, all designed compounds (MCPTD1-MCPTD8) possessed greater NLO responses than the reference compound (MCPTR). Interestingly,MCPTD7showed a smaller energy gap and remarkable NLO response amongMCPTD1-MCPTD8compounds. The highestμtotal, 〈α〉,βvecand 〈γ〉 values forMCPTD7were observed as 7.200, 2.40 × 10−22esu, 2.84 × 10−27esu and 8.6024 × 107esu, respectively. Aptitude towards the NLO material relied upon the position of different groups, the conjugated system donor and acceptor regions. The high NLO response reveals the fact that this class of pyrene-based derivatives with a thiophene linker has remarkable contributions towards NLO technological applications.