Investigation on crystal structure, phase transition behavior, and structural geometries of organic-inorganic hybrid [N(C3H7)4]2ZnBr4

Organic-inorganic hybrid compounds have attracted significant attention as a versatile class of functional materials owing to their unique structural characteristics and tunable physicochemical properties. In this study, colorless and transparent single crystals of [N(C₃H₇)₄]₂ZnBr₄ were grown from an aqueous solution. Thermal analyses (differential scanning calorimetry, differential thermal analysis), powder X-ray diffraction (XRD), and optical microscopy revealed a phase transition (TC) at 395 K, followed by decomposition and melting at 529 and 540 K, respectively. From the single-crystal XRD experiment, crystallographic analysis indicates a monoclinic symmetry (space group C2/c), with the unit cell dimensions a = 33.1977 Å, b = 14.2615 Å, c = 15.1130 Å, and β = 110.3840°, and remains thermally stable up to approximately 521 K. Solid-state nuclear magnetic resonance (NMR) results further support these findings: the ¹H and ¹⁴N magic angle spinning (MAS) NMR chemical shifts show discontinuous changes near the TC, while the ¹³C MAS NMR spectra exhibit variations in peak multiplicity, indicating a reduction in symmetry below the transition point. Moreover, the progressive line narrowing observed in the ¹H, ¹³C, and ¹⁴N spectra with increasing temperature reflects enhanced molecular motion, particularly reorientational dynamics associated with the TC.