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Anisotropic compressibility of the coordination polymer emim[Mn(btc)]
Author(s) -
Madsen Solveig R.,
Moggach Stephen A.,
Overgaard Jacob,
Brummerstedt Iversen Bo
Publication year - 2016
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520616005515
Subject(s) - compressibility , anisotropy , materials science , coordination polymer , polymer , chemical engineering , crystallography , thermodynamics , chemistry , composite material , physics , engineering , optics
The effect of pressure on the crystal structure of a coordination polymer, emim[Mn II (btc)] (emim = 1‐ethyl,3‐methyl imidazolium cation, btc = 1,3,5‐benzene‐tricarboxylate), was investigated with single‐crystal X‐ray diffraction. At 4.3 GPa the unit‐cell volume had decreased by 14% compared with ambient conditions. The unit‐cell contraction is highly anisotropic, with the a ‐ and b ‐axes decreasing by 5.5 and 9.5%, respectively, and the c ‐axis compressing a mere 0.25% up to 1.7 GPa followed by a 0.2% expansion between 1.7 and 4.3 GPa. The 0.2% increase in length of the c ‐axis in this interval happens above the quasi‐hydrostatic limit of the pressure‐transmitting medium and therefore it might be a consequence of strain gradients. Under ambient conditions, two MnO 6 units are connected by two carboxylate ligands to form dimeric units. On increasing pressure, a non‐bonded O atom from a bridging carboxylate group approaches the Mn atom, with the Mn—O distance decreasing from 2.866 (1) Å at 0.3 GPa to 2.482 (6) Å at 4.3 GPa, increasing the coordination environment of the Mn ion from six‐ to seven‐coordinated.