Synthesis, crystal structure, optical
and antimicrobial properties of 2-nitrobenzyl
triphenylphosphonium tetrabromocobaltate(II)

A novel organic-inorganic hybrid multifunctional crystalline material, 2-nitrobenzyl triphenylphosphonium tetrabromocobaltate(II) [2-NO₂BzTPP]₂[CoBr₄](1), has been synthesized using [2-NO₂BzTPP]Br and CoBr₂ in methanol solution acidified with hydrobromic acid and characterized using single-crystal X-ray diffraction and spectroscopic techniques. The single-crystal X-ray diffraction analysis showed that the hybrid [2-NO₂BzTPP]₂[CoBr₄](1) belongs to the triclinic space group P-1 with a = 11.1815(17) Å, b = 12.954(2) Å, c = 19.426(3) Å, α = 99.312(5)°, β = 100.654(5)°, γ = 113.746(5)°, V = 2442.3(7) Å³, Z = 2, which consists of two [2-NO₂BzTPP]⁺ cations and a [CoBr₄]^2– anion. The Co(II) ion in the [CoBr₄]^2– anion is coordinated to four Br^– ions and has a tetrahedral geometry. The C—H⋯O hydrogen bonds, O⋯p and O⋯Br interactions in the crystal can favor crystal stacking and stabilization. The bulk phase purity, homogeneity, and morphology of the desired compound are checked using powder XRD, and SEM-EDX analysis. The hybrid crystal showed an emission peak near 468 nm at room temperature under the excitation of UV light at 241 nm. The low energy gap (2.85 eV) indicated that the crystal was a semiconductor suitable for optical applications. Furthermore, the compound exhi­bited good bactericidal activity against E. coli and S. aureus.