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Proton sharing in bis(4-carbamoyl-pyridinium) squarate

Lookup NU author(s): Dr Ahmet Koroglu, Gary Nichol, Dr Ross Harrington, Emeritus Professor Bill CleggORCiD



Reaction in aqueous solution of nickel(II) squarate with isonicotinamide yielded well formed yellow crystals of the title compound, 2C6H 6N2O+·C4O42-, as a side product. The squarate dianion is bisected by a crystallographic twofold rotation axis, which passes through the centres of two opposite bonds of the ring. Crystal structure analysis reveals that, far from forming discrete ionic species, it is likely that there is a large degree of proton sharing between the anion and cation, with the H atom lying almost symmetrically between the donor and acceptor sites, as evidenced by the long N-H and short H⋯O distances [1.15 (3) and 1.39 (3) Å, respectively]. Other hydrogen bonding is more conventional, and there are weaker C-HO⋯ interactions contributing additional stability to the structure. © 2005 International Union of Crystallography.

Publication metadata

Author(s): Koroglu A, Bulut A, Ucar I, Nichol GS, Harrington RW, Clegg W

Publication type: Article

Publication status: Published

Journal: Acta Crystallographica Section C: Crystal Structure Communications

Year: 2005

Volume: 61

Issue: 12

Pages: o678-o680

ISSN (print): 0108-2701

ISSN (electronic): 1600-5759

Publisher: Wiley-Blackwell Publishing, Inc.


DOI: 10.1107/S0108270105032622


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