Study of chemically inequivalent N(CH3)4 ions in [N(CH3)4]2ZnBr4 near the phase transition temperature using 1H MAS NMR, 13C CP/MAS NMR,and 14N NMR

The temperature dependences of the chemical shifts and intensities of ¹H, ¹³C, and ¹⁴N nuclei in tetramethylammonium tetrabromozincate, [N(CH₃)₄]₂ZnBr₄, were investigated using single-crystal nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR spectroscopy to elucidate the structural geometry near the phase transition temperature. Based on the analysis of the ¹³C cross-polarization (CP)/MAS NMR and ¹⁴N NMR spectra, the two chemically inequivalent N(1) (CH₃)₄ and N(2) (CH₃)₄ ions were distinguished. Furthermore, the ¹⁴N NMR spectrum at the phase transition temperature indicated the existence of the ferroelastic characteristics of the N(CH₃)₄ ions.