New organic–inorganic bromide (P(C4H9)4)2[ZnBr4]: crystal structure, vibrational properties, and electrical conduction behavior from impedance studies

Abstract

There has been a lot of interest in the development of a novel hybrid material based on zinc with fascinating structural and physical properties. In this paper, a novel organic–inorganic hybrid (P(C₄H₉)₄)₂[ZnBr₄] crystal was synthesized via the slow evaporation method at room temperature and characterized by single-crystal X-ray diffraction, supported by density functional theory, vibrational spectroscopy and electrical analysis. At room temperature, it crystallizes in the monoclinic system (P2₁/c space group) with cell parameters a = 15.3260(11) Å, b = 17.6692(13) Å, c = 16.9898(11) Å, β = 114.715(2)°, V = 4179.4(5) ų and Z = 4. Its structure comprises two crystallographically independent organic (P(C₄H₉)₄)⁺ cations and one type of isolated [ZnBr₄]²⁻ anion. Each tetrahedral [ZnBr₄]²⁻ anion is surrounded by three tetrabutylphosphonium cations, forming multiple C–H⋯Br contacts that reinforce the structural framework. The density functional theory (DFT)-calculated Raman and IR spectra are in excellent agreement with the experimental data, allowing unambiguous assignment of vibrational modes, including metal–halogen stretches and the dynamics of the organic cations. Electrical impedance spectroscopy demonstrates temperature- and frequency-dependent conductivity with a negative temperature coefficient of resistance, indicating thermistor-like behavior. AC conductivity follows Jonscher's universal power law and is well described by the correlated barrier hopping model. These multifaceted findings establish (P(C₄H₉)₄)₂[ZnBr₄] as a multifunctional hybrid material suitable for integration into next-generation electronic and optoelectronic devices.