Theoretical study of static and frequency-dependent nonlinear optical properties of 1-phenyl-2,5-di(thiophen-2-yl)-1H-pyrrole based D-π-A chromophores through π-linkers modifications: A gateway towards giant nonlinear optical compounds

Abstract

Designing materials with proficient nonlinear optical (NLO) amplitudes is the frontier area of research. To address the briskly mounted demand for potentially useful NLO materials in optoelectronic and electrical applications, static and frequency-dependent NLO response properties of 1-phenyl-2,5-di(thiophen-2-yl)-1H-pyrrole (PDTP) based D-π-A chromophores were computed at 1907.21 nm, 532 nm, and 1064 nm laser wavelength for exploring SHG β (−2ω, ω, ω) and EOPE β (−ω, ω, 0). The PDTP-based organic dye (MC28) is selected to serve as a reference, and the quantum chemical models of its ten derivatives (SLN1-SLN10) are constructed by incorporating a variety of previously reported π-linkers into the reference. DFT and TD-DFT calculations reveal that π-linker modification tunes the NLO characteristics in SLN1-SLN10. The photophysical, electronic aspects, molecular electrostatic potential (MEP), frontier molecular orbital (FMO), density of state (DOS), transition density matrix (TDM), natural population analysis (NPA), and frequency-dependent NLO response properties of investigated dyes were evaluated. Giant NLO responses due to a much lower energy gap than the reference dye was found in SLN1-SLN10 confirmed by FMO analysis. UV–Vis analysis determined that the maximum absorption wavelength of the studied dyes was in the visible spectrum (383–413 nm). The proposed dye’s active NLO sensitivity and charge separation state was shown to have resulted from the migration of electrons from D to A via π-linkers using natural population analysis (NPA) analysis. In addition, molecular electrostatic potential (ESP), electron localization function (ELF), and localized orbital locator (LOL) topological assessments are carried out to evaluate the transfer of charge that takes place within SLN1-SLN10 as well as high NLO features. Maximum values of linear polarizability (αo) and first-hyperpolarizability (βo) were calculated to be 5.64 × 102 a.u. and 1.89 × 104 a.u., respectively in SLN3. At 1907.21 nm, SLN3 with terthiophene linker showed a remarkable SHG β(−2ω,ω,ω) and EOPE β (−ω,ω,0) response of 2.60 × 104 a.u. and 2.09 × 104 a.u. respectively. The theoretical structure provided conclusive evidence that the dyes under investigation possess excellent static and NLO potential at different laser wavelengths and should be considered for use in future NLO applications.