Molecular motion study of [N(CH3)4]2Zn1–xCux Cl4 (x = 0, 0.01, 0.1, 1) mixed crystals by 1H NMR relaxation

Abstract

AbstractThe temperature dependences of the 1H relaxation times in mixed crystals of formula [N(CH3)4]2Zn1–x Cux Cl4 (x = 0, 0.01, 0.1, and 1) were investigated. The phase transition temperatures and lattice constants of the mixed crystals were insensitive to the Cu impurity concentration. However, for relaxation above 290 K, deviations in the spin–lattice relaxation time, T1, and the spin–spin relaxation time, T2, on increasing x with respect to T1 and T2 observed for x = 0 were obtained. The experimentally observed 1/T1 above 290 K equals 1/T1r from reorientation motion plus 1/T1p due to paramagnetic Cu. From this result, the paramagnetic contribution to the proton relaxation rate is proportional to the abundance of paramagnetic impurities. From the results obtained it is concluded that the molecular motion is dependent on the concentration of the Cu impurity at high temperatures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)