Relaxation in anA2coupled spin system dissolved in a perdeuterated liquid crystal: The intermolecular dipolar random field cross relaxation term

摘要

A perdeuterated nematic liquid crystalNhyphen; (phyphen;ethoxybenzylidene) hyphen;phyphen;nhyphen;butylaniline (EBBAhyphen;d23, 98percnt; deuterium) was synthesized to study relaxation of small molecules dissolved in anisotropic solvents. Proton spinndash;lattice relaxation in the coupled A2spin system of methylene chloride (CH2Cl2) was studied using both perhydro and perdeutero EBBA as the solvent. The relaxation was modeled as intramolecular dipolendash;dipole interactions plus other mechanisms that were treated collectively as fluctuating external random magnetic fields. Comparison of relaxation in EBBA and EBBAhyphen;d23allowed the first experimental measurement of the correlation coefficient between external random fields at the two protons due to dipolar interactions of the methylene protons with the protons or deuterons of the solvent (78percnt; correlated). The selective nuclear Overhauser effect was also studied.