Dynamical disorder in 2-methyl-4-nitroaniline and its deuterated analogue crystals studied by Fourier transform infrared and nuclear magnetic resonance
Okwieka U.1, Hoderna-Natkaniec K.2, Misiaszek T.1, Medycki W.3, Baran J.4, Magdalena Szostak M.1
- 1Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, Wybrzee Wyspiańskiego 27, 50-370 Wroclaw, Poland
- 2Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland
- 3Institute of Molecular Physics, Polish Academy of Sciences, ul. Smoluchowskiego17, 60-179 Poznań, Poland
- 4Institute of Low Temperature and Structure Research, Polish Academy of Sciences, ul. Okólna 2, 50-422 Wroclaw, Poland
Journal of Chemical Physics, 131 (14), 144505, 2009
DOI:: 10.1063/1.3243855
Abstract:
The Fourier transform infrared spectra of the thin layers of 2-methyl-4-nitroaniline (MNA) and its deuterated analog were recorded in the 500-4000cm -1 region in the 10-300 K temperature range. Activation energies of the CH 3, - NH 2, and NO 2 groups reorientations were estimated. The H1 -NMR spin-lattice relaxation time, T 1, and the second moment of H1 -NMR resonance line, M 2, measured in the 80-298 K temperature range, were used to determine the parameters of the CH 3 group motion. The experimental potential barriers for the amine, nitro, and methyl group reorientations are considered in the context of strengths of the N- H ⋯ O, C- H ⋯O intermolecular hydrogen bonds, and other short contacts, recognized recently [U. Okwieka, J. Raman Spectrosc. 39, 849 (2008)], and they agree with the barriers calculated by quantum chemical methods. The dynamical disorder found in the MNA crystal in the large temperature range seems to be important from the point of view of its nonlinear optical and other properties. © 2009 American Institute of Physics.
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