Comprehensive structure–property–function correlation in three hybrid Bi(iii) and Sb(iii) metal halide compounds based on 4-ethylaminomethylpyridine: comparative insights into optical, dielectric, and antibiological activities

Abstract

Three new hybrid halometallates, (C₈H₁₄N₂)₂[Bi₂Br₁₀]·2H₂O (M4), (C₈H₁₄N₂)₃[BiCl₆]₂ (M43), and (C₈H₁₄N₂)[SbCl₅] (M41), have been comparatively investigated to establish comprehensive structure–property–function correlations. Single-crystal X-ray diffraction analysis revealed distinct zero-dimensional motifs based on Bi₂Br₁₀ dimers, BiCl₆ octahedra, and SbCl₅ square pyramids, with packing efficiencies ranging from 92.9 to 94.1%. These structural differences directly modulate their optical and dielectric properties: M4 exhibits broadband photoluminescence at 470 nm and an intermediate band gap of 2.90 eV; M43, the most distorted and least dense phase, displays a wide band gap of 3.16 eV with suppressed PL; and M41, with a nearly ideal square-pyramidal SbCl₅ geometry, shows the narrowest gap (2.77 eV) and a clean green–yellow emission at 571 nm, alongside dynamic dielectric relaxation processes. Antibacterial assays revealed exceptional activity for the organic cation and M41, surpassing that of gentamicin against both Gram-positive and Gram-negative strains, whereas M4 and M43 were significantly less active due to stronger ion pairing and reduced cation release. This integrated analysis highlights the pivotal roles of halide identity, metal coordination geometry, and lattice topology in dictating multifunctionality. The findings establish anion–cation engineering in halometallates as a versatile platform for designing materials that simultaneously combine optical, dielectric, and antibacterial properties.