Synthetic approach to achieve halo imine units: Solid-state assembly, DFT based electronic and non linear optical behavior

[Display omitted] •Synthesis of crystalline schiff base and SC-XRD analysis.•Hirshfeld surface analysis for intermolecular interactions.•NBO findings revealed dominant hyper-conjugative transitions with higher stability.•Global reactivity parameters showed larger value of hardness.•NLO response of compounds showed outstanding NLO materials. Herein, two crystalline schiff bases: (E)-2,4-dibromo-6-(((3,4-dichlorophenyl)imino)methyl)phenol (DCBA) and (E)-2,4-dichloro-6-(((2,4,5-trichlorophenyl)imino)methyl)phenol(TCCA) were prepared by treating halo-substituted benzaldehydes with chloro-substituted aniline through condensation reaction. The crystal structures of DCBA and TCCA were confirmed by SC-XRD analysis, which unambiguously revealed that C-H···Br, C-Cl···π, and off-set π···π stacking interactions were the key aspects of crystal packing of DCBA, whereas π···π off-set stacking interactions were the main aspect ofcrystal packing of TCCA. Hirshfeld surface analysis had been implemented for the further probe of intermolecular interactions. Accompanying with experimental, DFT investigation had also been performed at M06/6-311G(d,p) level to analyze these crystalline architectures. By comparative analysis of geometrical parameters, an efficient agreement was observed between DFT and SC-XRD data. Additionally, natural bond orbital (NBO) findings revealed that most dominant hyper-conjugative transitions with higher stability (31.06 and 30.70 kcal/mol) had been examined for DCBA and TCCA, respectively, which may cause the stability of these molecules. Further, global reactivity parameters disclosed that both compounds showed larger value of hardness (η = 2.181–2.205 eV) with least value of softness (σ = 0.226–0.229 eV) which indicated them kinetically enormous stable and show excellent concurrence with NBO and SC-XRD. The band gaps of DCBA and TCCA had been rationalized to be 4.40 and 4.36 eV, respectively. Interestingly, significant values of dipole moment [µtotal = 1.03 and 4.16 a.u.], linear polarizability [=309 and 1167.51 a.u.] and second order hyperpolarizability [ =3.90–4.18 × 105a.u.] were investigated in the entitled compounds. Remarkable NLO response of aforesaid compounds designated them as outstanding NLO materials for the hi-tech optoelectronic applications.