Structure, spectroscopy and DFT calculations of 1,2-di(3-hydroxymethylpyridinium)ethane dibromide

• X-ray structure of 1,2-di(3-hydroxymethylpyridinium)ethane dibromide.
• The dication and hydrogen-bonded anions are located on the inversion centre.
• The CH2OH groups interact with bromide anions by hydrogen bonds.
• The complex is stabilized by the N+⋯Br− electrostatic attractions.
• The IR and Raman spectra are predicted with DFT method followed by PED analysis.

The molecular structure of 1,2-di(3-hydroxymethylpyridinium)ethane dibromide (1) has been characterized by X-ray diffraction, B3LYP/6-311++G(d,p) calculations, FTIR, Raman and NMR spectra. The crystals are monoclinic, space group C2/c. 1,2-Di(3-hydroxymethylpyridinium)ethane dication and hydrogen-bonded bromide anions in crystals are located at the inversion center. The both CH2OH groups are engaged in two equal length hydrogen bonds with bromide anions. Two structures (2) and (3) were optimized at the B3LYP/6-311++G(d,p) level of theory. The optimized complex (2) resembles the crystal structure, while complex (3) is preferred energetically. The O⋯Br− hydrogen bonds distances are: 3.289(2) Å in crystals (1), but in the optimized structures (2) and (3) they are 3.303 Å and 3.461 Å, respectively. The investigated complex is additionally stabilized by the N+⋯Br− electrostatic attractions. The potential energy distributions (PED) were used for the assignments of IR and Raman frequencies in the experimental and calculated spectra of the title compound. The FTIR spectrum of (1) is consistent with the X-ray results. Interpretation of the 1H and 13C NMR spectra in DMSO-d6 has been based on 2D experiments. The calculated GIAO/B3LYP/6-311++G(d,p) magnetic shielding constants have been used to predict 1H and 13C chemical shifts for the optimized structures of (2) and (3).

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