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Vibrational study of the structure and polarons in piperazine hexahydrate
Author(s) -
Kanesaka Isao,
Kuwano Kazuhiko,
Ishioka Tsutomu
Publication year - 1995
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250260405
Subject(s) - polaron , raman spectroscopy , chemistry , piperazine , lattice (music) , phase transition , hydrogen bond , enthalpy , condensed matter physics , crystallography , physics , molecule , thermodynamics , optics , organic chemistry , quantum mechanics , electron , acoustics
The Raman spectrum of piperazine hexahydrate was observed over the whole wavenumber region at various temperatures (300—29 K). The splitting between the N—H stretch and the polaron was found to be 21 cm −1 at 44 K. The bands due to the axial configuration of piperazine were above 200 K in both the H and D systems. The enthalpy difference in the equatorial—axial equilibrium was calculated to be 8.1 and 7.6 kJ mol −1 in the H and D systems, respectively. The phase transition was found at ca. 170 K, and is ascribed to the order—disorder type associated with the axial configuration. The polaron was discussed group theoretically and reinvestigated on the basis of the coupling of the N—X stretch with optical lattice modes. It is noted that the polaron is little affected by the phase transition at 170 K or disorder in hydrogen positions.