title: High resolution NMR study of T1 magnetic relaxation dispersion. III. Influence of spin 1/2 hetero-nuclei on spin relaxation and polarization transfer among strongly coupled protons.
abstract: Effects of spin-spin interactions on the nuclear magnetic relaxation dispersion (NMRD) of protons were studied in a situation where spin ½ hetero-nuclei are present in the molecule. As in earlier works [K. L. Ivanov, A. V. Yurkovskaya, and H.-M. Vieth, J. Chem. Phys. 129, 234513 (2008); S. E. Korchak, K. L. Ivanov, A. V. Yurkovskaya, and H.-M. Vieth, ibid. 133, 194502 (2010)], spin-spin interactions have a pronounced effect on the relaxivity tending to equalize the longitudinal relaxation times once the spins become strongly coupled at a sufficiently low magnetic field. In addition, we have found influence of (19)F nuclei on the proton NMRD, although in the whole field range, studied protons and fluorine spins were only weakly coupled. In particular, pronounced features in the proton NMRD were found; but each feature was predominantly observed only for particular spin states of the hetero-nuclei. The features are explained theoretically; it is shown that hetero-nuclei can affect the proton NMRD even in the limit of weak coupling when (i) protons are coupled strongly and (ii) have spin-spin interactions of different strengths with the hetero-nuclei. We also show that by choosing the proper magnetic field strength, one can selectively transfer proton spin magnetization between spectral components of choice.
authors.affiliation: Institut für Experimentalphysik, Freie Universität Berlin Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Sergey E
authors.initials: SE
authors.lastname: Korchak
authors.forename: Konstantin L
authors.initials: KL
authors.lastname: Ivanov
authors.forename: Andrey N
authors.initials: AN
authors.lastname: Pravdivtsev
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Yurkovskaya
authors.forename: Robert
authors.initials: R
authors.lastname: Kaptein
authors.forename: Hans-Martin
authors.initials: HM
authors.lastname: Vieth
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011522:Protons
chemical_list: D000814:Aniline Compounds; D011522:Protons; C043454:2,4-difluoroaniline