Evolution of crystal structure of dual layered molecular conductor (ET)ZnBr(CHCl) with temperature

Electrical resistivity measurements of a dual layered organic conductor (ET) 4 ZnBr 4 (1,2-C 6 H 4 Cl 2 ) above room temperature show abrupt changes in resistivity at 320 K. Single-crystal X-ray diffraction studies in the 100-350 K range show polymorphic transformation at T p ∼320 K, indicating that...

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Published in:CrystEngComm 2021-09, Vol.23 (37), p.662-6625
Main Authors: Shilov, Gennady V, Zhilyaeva, Elena I, Aldoshin, Sergey M, Flakina, Alexandra M, Lyubovskii, Rustem B, Pesotskii, Sergei I, Lyubovskaya, Rimma N
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Summary:Electrical resistivity measurements of a dual layered organic conductor (ET) 4 ZnBr 4 (1,2-C 6 H 4 Cl 2 ) above room temperature show abrupt changes in resistivity at 320 K. Single-crystal X-ray diffraction studies in the 100-350 K range show polymorphic transformation at T p ∼320 K, indicating that the crystals belong to the tetragonal system (high-temperature phase, HT-phase) above T p and to the triclinic system (low-temperature phase, LT-phase) below T p with abrupt phase transition from the HT-phase to the LT-phase. During the sequential heating of the crystal, anharmonic effects are detected in the 260-315 K range: i) an increase in growth of rate of parameter a and rate of the mean-square atomic displacements of the [ZnBr 4 ] 2− anions; ii) an increase in the amplitudes of thermal vibrations of ET and solvent molecules. The structure near the phase transition at 315 K reveals splitting of the positions of ethylene groups of ET, demonstrating for the first time that for the (ET) 4 MBr 4 (1,2-C 6 H 4 Cl 2 ) family disordering of the ET occurs in the LT-phase when approaching T p . The final rearrangement of the structure from the triclinic LT-phase to the tetragonal HT-phase occurs above 315 K. Disordering of ET in dual-layered organic metal with incoherent interlayer electron transport (ET) 4 ZnBr 4 (C 6 H 4 Cl 2 ) begins already in the LT-phase when approaching T p .
ISSN:1466-8033
DOI:10.1039/d1ce00902h