Structural and motional study of pyridinium tetrahalogenoantimonates(III) by means of nuclear quadrupole resonance spectroscopy

Abstract

The temperature dependences of ³⁵Cl and ⁸¹Br nuclear quadrupole resonance (n.q.r.) frequencies, ³⁵Cl nuclear quadrupolar spin–lattice relaxation time T₁, and the ¹H n.m.r. second moment were observed for [C₅H₅NH][SbCl₄], [C₅H₅NH][SbBr₄], and their N-deuteriated analogues. The β phase of the chloride exhibited a second-order transition at 232 K similar to the phase transition of the bromide at 253 K. The phase transition points of the deuteriated compounds are lower by ca. 4 K for the chloride and ca. 5 K for the bromide. A minimum in ³⁵Cl T₁ was observed at about 125 K for the chloride and its deuteriated compound. This minimum is responsible for the reorientation of the pyridinium cation.