Exploration the influence of electron donor engineering on frequency-dependent nonlinear optical properties of anthraquinone-based chromophores: a DFT-ML approach

Recently, non-linear optical materials (NLO) have gained significant attention due to their applications in photonics, optical communication, and signal processing. Herein, anthraquinone core-based chromophores (APCD1–APCD7) were designed via donor engineering for efficient nonlinear optical materials. Their structural and optoelectronic properties were calculated by density functional theory and time dependent density functional theory (DFT/TD-DFT) at M06/6-311G (d, p) level. The designed chromophores (APCD1–APCD7) showed red-shifted absorption spectrum (380.89–466.58 nm ) and reduced HOMO LUMO energy gap of 1.99 − 3.81 eV . The density of states (DOS), transition density matrix (TDM) and natural bond orbital (NBO) analyses revealed efficient charge redistribution. Moreover, the designed compounds exhibited enhanced NLO responses, with APCD1 showing the strongest second-order NLO response, including β(− 2ω;ω,ω) of 7.11 × 10⁻²⁷ esu , whereas APCD5 exhibited the most pronounced third-order NLO response, with γ DFWM of 3.10 × 10⁻³¹ esu and n₂ of 5.01 × 10⁻¹⁴ cm²/W at 532 nm . Machine learning analysis established the structure–property relationship of the energy gap, identifying PEOE VSA 11, EState VSA 10, and BCUT2D VSA 11 as the most influential descriptors. Synthetic accessibility analysis indicates the practical feasibility of the designed chromophores, highlighting their potential for advanced photonic and optoelectronic applications.