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Issue 12, 2016
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Crystal structure and physical properties of 1-methyl-3-(carboxymethyl)benzimidazolium betaine·CuBr2 in crystal and water solution

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Abstract

A new Cu(II) carboxylate coordinating compound [1-methyl-3-carboxymethyl benzimidazolium betaine]2CuBr2 was synthesized and crystallized. The crystal has the triclinic symmetry P[1 with combining macron], with unit cell dimensions a = 7.9693, b = 8.4129, c = 9.1302 Å, α = 68.058, β = 85.402 and γ = 71.258 deg. (Z = 1), and molecules stacked along the a-axis. Cu(II)-complexes are planar and four-coordinated with chromophore CuO2Br2, where two oxygen atoms belong to the carboxylate groups of two betaines acting as unidentate ligands. The compound was characterized by two-dimensional 1H and 13C NMR spectroscopy for the determination of the correlation between protons of a ligand molecule. NMR spectra confirm the coordination of Cu(II) ions and allow identification of H(2) proton as easily detached in basic conditions. FT-IR spectra confirm the unidentate coordination of the betaine carboxylate group. UV-Vis spectra show three bands in d–d-transition region. Energies of these transitions were used in the interpretation of the EPR results. From powder and single crystal EPR measurements the g-factors were determined as gx = 2.072, gy = 2.030, gz = 2.241. A non-typical g-factor sequence is a consequence of the orbital mixing in the ground state of Cu(II) complex of D2h symmetry. The g-factors were interpreted in terms of the Molecular Orbital (MO) theory which delivered the Cu(II) unpaired electron density delocalization onto the ligand molecules. A strong delocalization on betaine molecules via in-plane ground-state orbital was found and unexpectedly also via out-of plane orbital directed towards the non-coordinating oxygen of the betaine carboxylate group.

Graphical abstract: Crystal structure and physical properties of 1-methyl-3-(carboxymethyl)benzimidazolium betaine·CuBr2 in crystal and water solution

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Publication details

The article was received on 11 Oct 2016, accepted on 09 Nov 2016 and first published on 10 Nov 2016


Article type: Paper
DOI: 10.1039/C6NJ03192G
Citation: New J. Chem., 2016,40, 10526-10535
  • Open access: Creative Commons BY license
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    Crystal structure and physical properties of 1-methyl-3-(carboxymethyl)benzimidazolium betaine·CuBr2 in crystal and water solution

    Ł. Czekański, S. K. Hoffmann, P. Barczyński, A. Gąsowska, R. Bregier-Jarzębowska, A. Zalewska, J. Goslar, M. Ratajczak-Sitarz and A. Katrusiak, New J. Chem., 2016, 40, 10526
    DOI: 10.1039/C6NJ03192G

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