Crystal structures, phase transitions, and nuclear magnetic resonance of organic–inorganic hybrid [NH2(CH3)2]2ZnBr4 crystals

Abstract

Organic–inorganic hybrid [NH₂(CH₃)₂]₂ZnBr₄ crystals were grown via slow evaporation, and their monoclinic structure was determined using single-crystal X-ray diffraction (XRD). The two phase transition temperatures at 401 K (T_C1) and 436 K (T_C2) were defined using differential scanning calorimetry and powder XRD. In the nuclear magnetic resonance spectra, a small change was observed in the ¹H chemical shifts for NH₂, ¹³C chemical shifts for CH₃, and ¹⁴N resonance frequency for NH₂ near T_C1. ¹H spin-lattice relaxation times T_1ρ and ¹³C T_1ρ for NH₂ and CH₃, respectively, rapidly decreased near T_C1, suggesting that energy was easily transferred. NH₂ in the [NH₂(CH₃)₂]⁺ cation was significantly influenced by the surrounding environments of ¹H and ¹⁴N, indicating a change in the N–H⋯Br hydrogen bond with the coordination geometry of the ZnBr₄ anion. These fundamental properties open efficient avenues for the development of organic–inorganic hybrids, thus qualifying them for practical applications.