Structure-property relationships in morpholinium hexahalostannate(IV) hybrid materials: Impact of halide substitution on optical and nonlinear responses

Two novel morpholinium-based organic-inorganic hybrid halostannates, (MorphH₂)SnCl₆.2Cl, (1), and (MorphH₂)SnBr₆.2H₂O (2), {(Morph)= (4-(2-ammonioethyl)morpholin-4-ium)} were synthesized using slow evaporation at room temperature technique and carefully characterized. Single-crystal X-ray diffraction validated nearly perfect octahedral geometries surrounding the Sn(IV) centers in both compounds. The Hirshfeld surface and 2D-fingerprintplot analysis indicated predominant halogen and hydrogen bonding, which enhances supramolecular stability. Optical tests revealed a notable halide-dependent redshift in the direct band gap, diminishing from 4.36 eV (Cl⁻) to 2.99 eV (Br⁻), with photoluminescence investigations supporting this observation. Z-scan measurements revealed significant third-order nonlinear optical (NLO) responses, with χ⁽³⁾ values of 9.22 × 10⁻¹² esu for sample (1) and an exceptional 5.00 × 10⁻¹¹ esu for sample (2). Moreover, frequency and temperature-dependent dielectric analysis elucidated space charge and dipolar relaxation mechanisms. These findings highlight the efficacy of halide substitution, hydration state and crystal symmetry in modulating the structural and functional characteristics of tin-based hybrids, establishing them as viable candidates for photonic, nonlinear optical, and dielectric device applications.