Convenient and facile theoretical design strategy to amplify NLO response of N-doped-indolo[3,2,1-jk]carbazole push–pull A-π-D-π-A switches

BACKGROUND: Nonlinear optical (NLO) materials play a crucial role in various technological fields, making it important to develop strategies that enhance their properties. This research paper focuses on the design strategy to enhance the NLO response of indolo[3,2,1-jk]carbazole-based N-doped fused-ring electron acceptors as its five new A-π-D-π-A switches. RESULTS: The chromophores IC1–IC5 were studied for their electronic, NLO, charge transfer, UV–visible and natural bond orbital-related features. Their energy levels were determined, with IC1 having the highest energy (3.12 eV) and IC5 the lowest energy (1.916 eV). Their corresponding maximum absorption wavelengths (λ_max) were determined to range from 398 to 647 nm. Their electronegativity (x), chemical potential (μ), hardness (η), softness (σ) and electrophilicity of the chromophores were also analyzed, having values ranging from 3.00 to 3.47 eV, 47 to −3.0 eV, 0.25 to 1.39 eV, 0.36 to 2.04 eV and 3.23 to 23.81 eV, respectively. The η and σ values indicated the stability and reactivity of the chromophores, with IC1 having the lowest η and highest σ values. IC2 had the highest dipole moment (μ_tot) (9.23D) and hyperpolarizability (β₀) of 10.323 × 10⁻¹¹ esu, indicating its strong NLO response. Among all, chromophore IC1 demonstrated a robust stabilization energy by its (N1) → (C15–C17)π* transition. CONCLUSION: The proposed theoretical design strategy successfully amplifies the NLO response of N-doped-indolo[3,2,1-jk]carbazole switches to open up possibilities for the development of advanced NLO materials, paving the way for future applications in photonics, optoelectronics and other emerging technologies.