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Synthesis, Structural and Sorption Characterization of a Hofmann Compound, Ni(3-Methy-4,4'-bipyridine)[Ni(CN)4]

Published

Author(s)

Winnie Wong-Ng, Jeffrey T. Culp, Daniel Siderius, Yu-Sheng Chen, S. Y. G. Wang, Andrew J. Allen, Eric J. Cockayne

Abstract

Crystal structure of the guest-free Ni(CN)4-based metal organic framework Ni(3-Methy-4,4'-bipyridine)[Ni(CN)4] (nicknamed Ni-BpyMe(A)), was determined to be orthorhombic, Pmma, a= 12.6025(4) Å, b=7.3324(3) Å, c=11.3095(4) Å, V=1045.07 (2) Å3 and Z=2. Acetone extraction of crystalline Ni-BpyMe(dimethyl sulfoxide "DMSO" guests) followed by evacuation yielded the guest-free crystalline framework. The structure of Ni-BpyMe(A) consists of a 3-D net built from extended 2-D [Ni(CN)4] groups. These layers are connected to each other via the BpyMe ligands at the six-fold coordinated Ni2 site while Ni1 has a four-fold coordination environment. While forming infinite square nets, the [Ni(CN)4] chains progress in a zig-zag fashion along the ab-direction; they can be projected along a or b directions. Another feature of this structure is that instead of locating the -CH3 group in one position of the pyridine ring as expected, it appears to be in two mirror-related positions on the same pyridine ring. The structure represents an average of two configurations which gives rise to the pseudosymmetry. The methyl group is distributed equally among each side of the pyridine ring; therefore, the occupancy of the methyl group is 50%. The compound exhibits a Type-I sorption characteristics. The absence of a hysteresis loop indicates that it is not likely a flexible MOF. A comparison of the structure of guest-free Ni-BpyMe(A) with a previously reported structure of Ni-BpyMe(D) which contained DMSO molecules revealed a significant increase in the bipyridyl dihedral angle from 34.87° to 90.00° after removal of the guest solvent molecules in the pores. The change in ring orientation of the BpyMe ligands stabilize the pore structure against collapse. The structural change is relevant to gate opening behaviors observed in other MOFs although no gating behavior was indicated in the gas adsorption behavior.
Citation
Polyhedron
Volume
200

Keywords

Metal organic framework, Ni(3-Methy-4, 4’-bipyridine)[Ni(CN)4], crystal structure, synchrotron radiation, sorption characterization, Carbon dioxide capture

Citation

Wong-Ng, W. , Culp, J. , Siderius, D. , Chen, Y. , Wang, S. , Allen, A. and Cockayne, E. (2021), Synthesis, Structural and Sorption Characterization of a Hofmann Compound, Ni(3-Methy-4,4'-bipyridine)[Ni(CN)4], Polyhedron, [online], https://doi.org/10.1016/j.poly.2021.115132, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=930709 (Accessed August 14, 2022)
Created March 6, 2021, Updated October 14, 2021