Interpretation of the crystal growth, phase transition, and molecular dynamics of [N(CH3)4]2ZnBr4 crystals by replacing partially the Zn2+ ions with Co2+ ions

Abstract

The effects on the physical properties of [N(CH3)4]2Zn1-xCoxBr4 (x = 0, 0.5, 0.7, and 1) crystal due to the partial substitution of Zn2+ ions with paramagnetic Co2+ ions were discussed. The crystal structures and phase transition temperature (287 K) of layered perovskite-type [N(CH3)4]2Zn1-xCoxBr4 were nearly unaffected by the partial doping of Co2+ ions, as revealed by X-ray diffraction and differential scanning calorimetry experiments. The environments surrounding the 1H and 13C in [N(CH3)4]2Zn1-xCoxBr4 mixed systems were determined from the chemical shifts and the spin-lattice relaxation time T1ρ of 1H magic angle spinning nuclear magnetic resonance (MAS NMR) and 13C cross-polarization (CP)/MAS NMR. The molecular motions by the T1ρ for 13C nuclei were nearly unaffected when Zn2+ ions were substituted with Co2+ ions, whereas those for 1H nuclei were influenced by doping Co2+ ions. A comparison of the molecular dynamics of TMA-Zn1-xCoxBr4 studied in this paper with the previously reported TMA-Zn1-xCoxCl4 was made to understand the effects of Cl and Br ions.