Phase transition, thermal dissociation and dynamics of NH3 ligands in [Cd(NH3)4](ReO4)2

Łukasz Hetmańczyk; Joanna Hetmańczyk

doi:10.1016/j.saa.2016.03.045

Phase transition, thermal dissociation and dynamics of NH3 ligands in [Cd(NH3)4](ReO4)2

Spectrochim Acta A Mol Biomol Spectrosc. 2016 Jul 5:164:24-32. doi: 10.1016/j.saa.2016.03.045. Epub 2016 Apr 4.

Authors

Łukasz Hetmańczyk¹, Joanna Hetmańczyk²

Affiliations

¹ Jagiellonian University, Faculty of Chemistry Department of Chemical Physics, Ingardena 3, 30-060 Cracow, Poland; Joint Institute for Nuclear Research, Frank Laboratory of Neutron Physics, 141980 Dubna, Russian Federation. Electronic address: hetmancz@chemia.uj.edu.pl.
² Jagiellonian University, Faculty of Chemistry Department of Chemical Physics, Ingardena 3, 30-060 Cracow, Poland; Joint Institute for Nuclear Research, Frank Laboratory of Neutron Physics, 141980 Dubna, Russian Federation.

PMID: 27070528
DOI: 10.1016/j.saa.2016.03.045

Abstract

High temperature phase transition in [Cd(NH3)4](ReO4)2 at Tc=368.5K (on heating) was reported for the first time. Thermal stability was investigated by thermal analysis methods. The titled compound decomposes in three main stages. The first two are connected with deamination process whereas in the last step Re2O7 evaporates. The activation energy for NH3 lost processes was estimated from TG measurements. The dynamics of NH3 ligands in the low temperature phase was probed by various complementary techniques. Temperature dependent band shape analysis of properly chosen infrared and Raman scattering vibrational bands was performed. It was found that activation energy for NH3 reorientational motion (below 300K) is rather small and is equal to ca. 4kJmol(-1). The quasielastic neutron scattering measurements revealed that NH3 groups perform fast stochastic reorientational motion even in the low temperatures. The neutron and X-ray powder diffraction data do not revealed any drastic changes in the crystal structure in the wide temperature range.

Keywords: IR and RS band shape analysis; Neutron scattering methods; TG kinetics analysis; Tetraamminecadmium rhenate(VII).

Publication types

Research Support, Non-U.S. Gov't