Optimization of electron distribution for enhancing the SHG output using electron withdrawing substituents: evidence from imidazole-picrate hybrid model

•imidazole-picrate hybrid crystals 1 & 2 are determined by single crystal XRD analysis.•imidazole-picrate hybrid crystals enhance nonlinear optical behavior crystals.•The relevant electronic and structural aspects of the crystals further experiments and computations were carried out.•DFT for additional understanding of the molecular design and optoelectronic properties. In our earlier report, we perceived that the frequency doubling behavior of imidazole-picrate hybrid crystals are high upon attaching electron withdrawing groups than electron donating one. Therefore, in order to enhance non-linear optical behavior of the imidazole-picrate hybrid crystals, we trialed with electron-withdrawing groups. Hence, In this report, the substitution of the electron-withdrawing -Cl (chlorine) or -OCH3 (methoxy) group at the phenyl ring found to enhance the second harmonic generation-nonlinear optical (SHG-NLO) property of the imidazole-picrate hybrid crystals. The total dipole moment (μtotal), electronegativity and hyperpolarizability (β0) of -Cl (compound 1) and -OCH3 (compound 2) substituted hybrids were assessed through computations to estimate the SHG-NLO abilities. Although both groups (-Cl,-OCH3) exhibit electrons withdrawing behavior, the higher values of μtotal, electronegativity, and β0 values computed for -Cl substituted imidazole-picrate hybrid crystals are the indicative factor for the superior NLO behaviour of 1. The computed μtotal, electronegativity and β0 of 1 and 2 infers that the substitution of strong electron withdrawing group; Cl in the phenyl ring of imidazole-picrate maximizes the uneven distribution of electrons than -OCH3. The measured SHG of value for the single crystal of 1 is comparatively higher than 2. SHG of 1 is 1.75 (times that of KDP) and 2 is 1.20 (times that of KDP). In order to, confirm and demonstrate the relevant electronic and structural aspects of the crystals further experiments and computations were carried out and reported. [Display omitted]