Synthesis, optical features, and electrical properties of a new antimony-based hybrid halide (C₈H₁₄N₂)[SbCl₅]

A new antimony-based organic-inorganic hybrid, (C₈H₁₄N₂)[SbCl₅], was synthesized by slow evaporation and characterized using complementary experimental and theoretical methods. Diffuse reflectance spectroscopy revealed a direct optical band gap of 2.77 eV, in close agreement with the DFT-predicted HOMO-LUMO gap of 2.7 eV. Under 259 nm excitation, the compound exhibits intense green-yellow photoluminescence at 571 nm, confirmed by CIE 1976 chromaticity coordinates. Differential scanning calorimetry shows three endothermic transitions (323, 358, 408 K) corresponding to structural reorganizations that modulate electrical behavior. Impedance spectroscopy evidences temperature-activated dielectric relaxation and strong interfacial polarization following a non-Debye mechanism. The modulus and conductivity analyses indicate multistep activation processes associated with phase transitions. DFT/TD-DFT calculations show charge transfer from [SbCl₅] orbitals toward the pyridyl π-system, supported by MEP, ELF, LOL, and RDG-NCI analyses identifying key non-covalent interactions that stabilize the framework. Collectively, these results highlight (C₈H₁₄N₂)[SbCl₅] as a structurally robust hybrid with tunable optical and dielectric responses suitable for photonic and thermally controlled optoelectronic applications.