The crystal structure of γ-bis(ethylammonium) tetrachloromanganate(II) at 126 K and its phase transition

Abstract

y-Bis(ethylammonium) tetrachloromanganate(II), stable below 225 K, is orthorhombic, space group Pbca, with a = 7.325 (8), b = 7.151 (11), c = 22.035 (19) A, Z = 4. Refinement for 1329 reflexions with I > 1.96a(I) measured at 126 K converged to R -0.040 and R w = 0.047. The perovskite-like layer of cornersharing MnC16 octahedra shows an a-a-c tilt system; the ethylammonium group takes one of the two orientations of the 13 form. The hydrogen bonding involves two axial C1(2) atoms and one equatorial CI(1) atom as acceptors. The phase transition is accomplished by a change of the tilt system (a-a-c --, a-a-c °) and by orientation switching of the ethylammonium group.

Spin Dynamics in the Paramagnetic Regime: NMR and EPR in Two-Dimensional Magnets

“…Their mean positions are known from X-ray diffraction [23]. The observed NMR signal then represents the superposition of 64 single proton contributions which -due to their different strengths of dipolar coupling -may differ both in relaxation times and resonance fields.…”

Raman spectroscopic study of structural phase transitions in the layer crystals (EtNH3)2MCl4with M=Cd and Mn

“…The structural phase transitions of EAMnC and EACdC have been studied by NMR (Blinc eta1 1977), crystallographic (Chapuis 1977, Depmeier 1977, Depmeier and Heger 1978, optical (Brunskill andDepmeier 1982, Karajamaki eta1 1981): dielectric , calorimetric (Tello et a1 1977) and infrared (Oxton 1979, Peyrard andPerret 1979) measurements. They are summarised in table 1.…”

Neutron diffraction study of twinned crystals of ethylenediammonium copper tetrachloride and ethylenediammonium manganese tetrachloride

“…In compounds of the first category the layers are held together essentially by van der Waals contacts between the aliphatic chains, which are hydrogen bonded to metal-C14 layers, while in the compounds of the second category hydrogen bonds between NH 3 groups at both ends of the aliphatic chains and CI atoms of the perovskite-type layer form a more rigid link between adjacent layers. Thermal motion of alkylammonium groups, deformation of metal-Cl4 framework and changes in the hydrogen-bonding scheme were shown to be responsible for phase transitions (Heger, Mullen & Knorr, 1976;Depmeier, 1977;Chapuis, Arend & Kind, 1975).…”