79Br and 127I NQR of tert-Butylammonium Halides and Crystal Structure of (CH3)3CNH3⊕ Br⊖

Abstract

AbstractThe 79Br and the 127 I NQR spectrum of tert-butylammonium bromide and iodide, respectively, was studied as a function of temperature. No phase transition was observed for the bromide in the temperature range covered. The 79Br NQR frequency is 9.056 MHz at 113 K and increases with increasing temperature (10.040 MHz at 293 K). The NQR spectrum reveals a phase transition of ( CH3 ) 3 CNH⊕3I⊖ around 360 K with pronounced hysteresis. The nuclear quadrupole coupling constant of 127 I is 69.335 MHz with an asymmetry parameter of 0.154 for the high temperature phase at T = 370 K. For the low temperature phase the corresponding values are 67.136 MHz and 0.081 at 300 K.The crystal structure of tert-butylammonium bromide was studied at room temperature. The compound crystallizes orthorhombic, space group D152hPbca, with 4 formula units in the unit cell, a = 1832.1 pm, b = 918.5 pm, c = 899.8 pm. The crystal structure and hydrogen bond system are discussed in connection with the NQR results.