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@ARTICLE{PiechaBisiorek:188412,
      author       = {Piecha-Bisiorek, A. and Bator, G. and Sawka-Dobrowolska, W.
                      and Sobczyk, L. and Rok, M. and Medycki, W. and Schneider,
                      G. J.},
      title        = {{S}tructure and {T}unneling {S}plitting {S}pectra of
                      {M}ethyl {G}roups of {T}etramethylpyrazine in {C}omplexes
                      with {C}hloranilic and {B}romanilic {A}cids},
      journal      = {The journal of physical chemistry / A},
      volume       = {118},
      number       = {34},
      issn         = {1520-5215},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {FZJ-2015-01810},
      pages        = {7159 - 7166},
      year         = {2014},
      abstract     = {The crystal and molecular structure of the
                      2,3,5,6-tetramethylpyrazine (TMP) complex with
                      2,5-dibromo-3,6-dihydroxy-p-quinone (bromanilic acid, BRA)
                      has been studied and the results are compared with TMP CLA
                      (2,5-dichloro-3,6-dihydroxy-p-quinone (chloranilic acid,
                      CLA) complex. The X-ray structure of TMP BRA complex
                      indicates the formation of dimeric units, in which two
                      BRA– anions are connected by two O–H···O (2.646(2)
                      Å) hydrogen bonds, whereas the cations and anions are
                      joined together by strong N+–H···O– (2.657(2) Å)
                      hydrogen bonds. The results are analyzed in terms of both
                      the methyl group surroundings and the C–H···O and
                      N+–H···O– (or N···H–O) bridge formations. Both
                      effects, the strength of the N+–H···O– hydrogen bonds
                      and steric hindrance for the rotations, are responsible for
                      the CH3 group dynamics. For the TMP CLA and TMP BRA
                      complexes, the inelastic neutron backscattering spectra were
                      also investigated. In the case of TMP CLA, four tunneling
                      signals have been observed in the energy range ±30 μeV,
                      which indicates four inequivalent methyl groups in the
                      crystal structure at the lowest temperature. No tunneling
                      splitting is observed in the case of the TMP BRA complex,
                      most probably due to the overlapping with the elastic peak.
                      The tunneling results are consistent with the 1H NMR
                      spin–lattice relaxation time investigations in a wide
                      temperature range, which also point to the CH3 group
                      tunneling effect in the case of TMP CLA.},
      cin          = {JCNS (München) ; Jülich Centre for Neutron Science JCNS
                      (München) ; JCNS-FRM-II / Neutronenstreuung ; JCNS-1 /
                      ICS-1},
      ddc          = {530},
      cid          = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-1-20110106 / I:(DE-Juel1)ICS-1-20110106},
      pnm          = {54G - JCNS (POF2-54G24)},
      pid          = {G:(DE-HGF)POF2-54G24},
      experiment   = {EXP:(DE-MLZ)SPHERES-20140101},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000341121000048},
      pubmed       = {pmid:25099129},
      doi          = {10.1021/jp5058429},
      url          = {https://juser.fz-juelich.de/record/188412},
}