The rotational hindrance potential of NH3 groups in Ni(NH3)6I2

Publisher Website
Google Scholar
Abstract
The INS librational spectra of Ni(NH3)6I2 and Ni(ND3)6I2 are shown to be consistent with the motions of a single‐type ammine rotor in a hindrance potential of the form cos(3φ). A barrier height of 18.6 meV is derived. The three peaks which arise in the spectrum of the tunnel‐split ground state are attributed to ammine:ammine interactions and do not simply reflect the local symmetry at the nickel atom. A qualitative study of the differing behavior of these three tunneling peaks on changes in temperature, partial deuteration, and pressure shows that the NH3:NH3 coupling is sensitive to the rotational states of neighboring groups and changes to the order parameter as the II–I phase transition is approached. Direct interaction of the NH3 groups with the anion seems to be very slight.