Hybrid tin (IV)-based heterocyclic compound with halogen acids: Crystal structure, DFT, Hirshfeld surface analysis and antioxidant investigations

A series of organic–inorganic hybrid materials were synthesized and subjected to comprehensive physicochemical characterization to elucidate their structural attributes, optical behaviour and antioxidant potential. Single-crystal X-ray diffraction analysis established that both compounds crystallize within the monoclinic crystal system, adopting the centrosymmetric P 1 21/c 1 space group, with two formula units per unit cell. Both compounds crystallize in the monoclinic system, where the α and γ angles are 90°, while the β angle deviates from 90°. The β values are 106.274(3) ° for (1) and 106.730(16) ° for (2) , confirming their monoclinic symmetry. The refined lattice parameters a = 8.2362(9) Å, b = 11.1477(12) Å, c = 11.8207(13) Å for compound (1) and a = 8.112(4) Å, b = 11.721(6) Å, c = 12.290(6) Å for compound (2) . Fourier-transform infrared spectroscopy confirmed the presence of characteristic functional groups, validating the molecular framework. UV-Visible absorption spectroscopy and photoluminescence studies unveiled cut-off wavelengths at 237 nm for (1) and 240 nm for (2) indicative of their optical bandgap characteristics. Under excitation wavelengths of 270 nm (1) and 276 nm (2) , the compounds exhibited intense emission maxima at 381 nm and 468 nm respectively, suggesting promising photophysical properties with potential applications in optoelectronics. The thermal behaviour of the synthesized hybrids was examined using TG-DTA, while SEM-EDS provided insights into surface morphology and elemental composition. BVS calculations confirmed the + 4-oxidation state of tin, and CSM analysis validated the octahedral geometry of the anionic units. DFT (B3LYP/LanL2DZ) optimized molecular geometries and MEP maps, supporting experimental findings. Hirshfeld surface analysis and fingerprint plots provided profound insights into the critical intermolecular interactions dictating crystal packing. The third-order nonlinear optical properties have been investigated by Z-scan method. Moreover, the DPPH assay demonstrated remarkable antioxidant activity, underscoring the potential biomedical applications of these materials. • Synthesized compounds and crystal structures are C 12 H 18 Cl 6 N 4 Sn ( 1) and C 12 H 18 Br 6 N 4 Sn (2). • Both crystals were examined using UV, photoluminescence, and thermal analysis. • CSM shows ideal octahedral geometry for both crystal anions. • Antioxidant activity, highlighting the promising biomedical applications of these materials.