This work reports anelastic spectroscopy measurements on the partially deuterated (ND3BH3 and NH3BD3) and perdeuterated (ND3BD3) ammonia borane (NH3BH3) compounds. The relaxations previously reported in NH3BH3 are observed in all the samples, and are ascribed to the rotational and torsional dynamics of NH(D)(3)BH(D)(3) complexes. A new thermally activated peak appears at 70 K (for a vibration frequency of similar to 1 kHz) in the spectrum of NH3BD3 and ND3BD3. The peak is practically a single-time Debye process, indicating absence of interaction between the relaxing units, and has a strikingly high intensity. A secondary relaxation process is also detected around 55 K. The anelastic spectrum of the ND3BH3 only displays this less intense process at 55 K. The analysis of the peaks supplies information about the dynamics of the relaxing species, and the obtained results provide indications on the effect of partial and selective deuteration on the hydrogen (deuterium) dynamics. (C) 2013 Elsevier B.V. All rights reserved.
Rotational dynamics in ammonia borane: Evidence of strong isotope effects / R., Cantelli; A., Paolone; O., Palumbo; Leardini, Fabrice; T., Autrey; A., Karkamkar; A. T., Luedtke. - In: JOURNAL OF ALLOYS AND COMPOUNDS. - ISSN 0925-8388. - ELETTRONICO. - 580:1(2013), pp. S63-S66. [10.1016/j.jallcom.2013.03.148]
Rotational dynamics in ammonia borane: Evidence of strong isotope effects
LEARDINI, FABRICE;
2013
Abstract
This work reports anelastic spectroscopy measurements on the partially deuterated (ND3BH3 and NH3BD3) and perdeuterated (ND3BD3) ammonia borane (NH3BH3) compounds. The relaxations previously reported in NH3BH3 are observed in all the samples, and are ascribed to the rotational and torsional dynamics of NH(D)(3)BH(D)(3) complexes. A new thermally activated peak appears at 70 K (for a vibration frequency of similar to 1 kHz) in the spectrum of NH3BD3 and ND3BD3. The peak is practically a single-time Debye process, indicating absence of interaction between the relaxing units, and has a strikingly high intensity. A secondary relaxation process is also detected around 55 K. The anelastic spectrum of the ND3BH3 only displays this less intense process at 55 K. The analysis of the peaks supplies information about the dynamics of the relaxing species, and the obtained results provide indications on the effect of partial and selective deuteration on the hydrogen (deuterium) dynamics. (C) 2013 Elsevier B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
