Phase transition and cationic motion in the perovskite formate framework [(CH3)2NH2][Mg(HCOO)3]

Tetsuo Asaji, Sho Yoshitake, Yoshiharu Ito, Hiroki Fujimori

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29 Citations (Scopus)


The dielectric phase transition of a metal-organic perovskite with a dimethylammonium cation, [(CH3)2NH2][Mg(HCOO)3], at Tc = 270 K was investigated using 1H nuclear magnetic resonance spectroscopy. The temperature dependence of the spin-lattice relaxation time T1, was measured to elucidate the methyl group reorientation and cation reorientation. The results was very similar to that of the zinc analog, [(CH3)2NH2][Zn(HCOO)3], previously reported. The cationic motion was expected to be the 120° reorientation of the dimethylammonium ion around the axis through the two carbon atoms of the cation. The activation energy for cationic motion was determined to be 22.7 kJ mol-1. The two methyl groups of the cation in the low-temperature phase become nonequivalent and have activation energies of 9.1 and 7.0 kJ mol-1 for reorientation about the methyl group C3-axis. The T1 measurements indicated that the Tc = 270 K phase transition is of first-order and another first-order phase transition was revealed at around 80 K. The transition entropy was estimated to be ΔS = 10 ± 1 J K-1 mol-1 for the Tc = 270 K phase transition in agreement with the simple three fold order-disorder model of dimethylammonium ion.

Original languageEnglish
Pages (from-to)719-723
Number of pages5
JournalJournal of Molecular Structure
Publication statusPublished - 5 Nov 2014


  • Metal-organic framework
  • NMR
  • Phase transition
  • Spin-lattice relaxation


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