Please use this identifier to cite or link to this item: https://hdl.handle.net/10593/22314
Title: Supramolecular structure of the 1:2 complex of 1,4-dimethylpiperazine mono-betaine with squaric acid
Authors: Dega-Szafran, Zofia
Katrusiak, Andrzej
Komasa, Anna
Szafran, Mirosław
Keywords: X-ray diffraction
electrostatic interactions
DFT calculations
FTIR and NMR spectroscopy
hydrogen bonds
squaric acid
Issue Date: 1-Jul-2013
Citation: SUPRAMOLECULAR CHEMISTRY 25 (7) 432-440
Abstract: The 1: 2 complex of 1,4-dimethylpiperazine mono-betaine (MBPZ) with squaric acid (H(2)SQ) has been characterised by single-crystal X-ray analysis, FTIR and NMR spectroscopies, and by DFT calculations. The crystals are monoclinic, space group P2(1)/c. Two MBPZ cations and four hydrogen squarate anions (HSQ(-)) are linked by strong O(1)=H center dot center dot center dot O(13) (2.525(4) angstrom), O(14)-H center dot center dot center dot O(21) (2.511(4) angstrom) and N(4)-H center dot center dot center dot O(23) (2.607(3)angstrom) hydrogen bonds into a cyclamer R-6(6)(38). In turn, the cyclamers are linked into a helix C-4(4)(20) through two O(24)-H center dot center dot center dot O(11) hydrogen bonds of 2.516(4)angstrom. The piperazinium ring has a chair conformation with N(4)-CH3 and N(1)-CH2COOH substituents in the equatorial positions, and N(1)-CH3 in the axial position. The FTIR spectrum is consistent with the crystal data. Two models of the 1: 2 complex of MBPZ with H(2)SQ have been optimised at the B3LYP/6-311++G(d,p) level of theory and have been used to calculate harmonic IR frequencies. One of the models (2) is dominated by electrostatic attraction between NH(4)(+) and HSQ(-), whereas in the other (3) squaric acid interacts with a zwitterionic MBPZ through the O-H center dot center dot center dot O and O-H center dot center dot center dot N hydrogen bonds.
URI: http://hdl.handle.net/10593/22314
ISSN: 1061-0278
Appears in Collections:Artykuły naukowe (WCh)

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