Ferrimagnetic Ordering and Anomalous Stoichiometry Observed for the Cubic, Extended 3D Prussian Blue Analogues (NEt3Me)2MnII5(CN)12 and (NEt2Me2)2MnII5(CN)12: A Cation‐Adaptive Structure

The reactions of MnII(O2CCH3)2 with NEt3Me+CN− and NEt2Me2+CN− form (NEt3Me)2MnII5(CN)12 (1) and (NEt2Me2)2MnII5(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 exten...

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Bibliographic Details
Published in:Chemistry : a European journal 2020-12, Vol.26 (67), p.15565-15572
Main Authors: Graham, Adora G., Lapidus, Saul H., Hawkins, Casey G., Stephens, Peter W., Miller, Joel S.
Format: Article
Language:English
Subjects:
Antiferromagnetism
Cations
Chemical bonds
Chemistry
Coercivity
cyanometallates
extended 3D structures
ferrimagnet
Ferrimagnetism
Inflection points
Magnetization
manganese
Optimization
Pigments
Rietveld analysis
Smart structures
Stoichiometry
Synchrotrons
Void space
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Summary:The reactions of MnII(O2CCH3)2 with NEt3Me+CN− and NEt2Me2+CN− form (NEt3Me)2MnII5(CN)12 (1) and (NEt2Me2)2MnII5(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 MnII sites in a 3:2 ratio. Each tetrahedral MnII site is surrounded by four low‐spin octahedral MnII sites, and each octahedral MnII site is surrounded by six high‐spin tetrahedral MnII sites; adjacent sites are antiferromagnetically coupled in 3D. Compensation does not occur, and magnetic ordering as a ferrimagnet is observed at Tc=13 K for 2 based on the temperature at which remnant magnetization, Mr(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, Mr, of 2050 emuOe mol−1. The unusual structure and stoichiometry are attributed to the very ionic nature of the high‐spin N‐bonded MnII 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 AxMnIIy(CN)x+2y (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. Complex cube: The family of A2MnII5(CN)12 (A=NEt3Me, NEt2Me2) has a very complex cubic structure. Model‐building and diffraction data revealed an extended 3D cubic motif with adjacent tetrahedral and octahedral MnII sites. Antiferromagnetic coupling between the high‐spin (S=5/2) tetrahedral and low‐spin (S=1/2) octahedral sites is not compensated and leads to ordering as a ferrimagnet.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.202000586