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Ferrimagnetic Ordering and Anomalous Stoichiometry Observed for the Cubic, Extended 3D Prussian Blue Analogues (NEt 3 Me) 2 Mn II 5 (CN) 12 and (NEt 2 Me 2 ) 2 Mn II 5 (CN) 12 : A Cation‐Adaptive Structure
Author(s) -
Graham Adora G.,
Lapidus Saul H.,
Hawkins Casey G.,
Stephens Peter W.,
Miller Joel S.
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202000586
Subject(s) - ferrimagnetism , crystallography , octahedron , magnetization , rietveld refinement , stoichiometry , chemistry , manganese , crystal structure , neutron diffraction , materials science , physics , magnetic field , organic chemistry , quantum mechanics
The reactions of Mn II (O 2 CCH 3 ) 2 with NEt 3 Me + CN − and NEt 2 Me 2 + CN − form (NEt 3 Me) 2 Mn II 5 (CN) 12 ( 1 ) and (NEt 2 Me 2 ) 2 Mn II 5 (CN) 12 ( 2 ), respectively. Structure model‐building and Rietveld refinement of high‐resolution synchrotron powder diffraction data revealed a cubic [ a= 24.0093 Å ( 1 ), 23.8804 Å ( 2 )] 3D extended structural motif with adjacent tetrahedral and octahedral Mn II sites in a 3:2 ratio. Each tetrahedral Mn II site is surrounded by four low‐spin octahedral Mn II sites, and each octahedral Mn II site is surrounded by six high‐spin tetrahedral Mn II sites; adjacent sites are antiferromagnetically coupled in 3D. Compensation does not occur, and magnetic ordering as a ferrimagnet is observed at T c =13 K for 2 based on the temperature at which remnant magnetization, M r ( T )→0. The hysteresis has an unusual constricted shape with inflection points around 50 and 1.2 kOe with a 5 K coercivity of 16 Oe and remnant magnetization, M r , of 2050 emuOe mol −1 . The unusual structure and stoichiometry are attributed to the very ionic nature of the high‐spin N‐bonded Mn II ion, which enables the maximization of the attractive van der Waals interactions through minimization of void space via a reduced ∠ MnNC. This results in an additional example of the A x Mn II y (CN) x +2 y ( x= 0, y= 1; x= 1, y= 3; x= 2, y= 1; x= 2, y= 2; x= 2, y= 3; x= 3, y= 5; and x= 4, y= 1) family of compounds possessing an unprecedented stoichiometry and lattice motif that are cation adaptive structured materials.