The Complex of N-methylmorpholine Betaine with 3,4-dinitrophenol Studied by FTIR, UV, NMR Spectroscopies, X-ray Diffraction and DFT Calculations

Zofia Dega-Szafran 1Andrzej Katrusiak Mirosław Szafran 

1. Adam Mickiewicz University, Faculty of Chemistry, Grunwaldzka 6, Poznań 60-780, Poland

N-methylmorpholine betaine forms a crystalline 1:1 complex with 3,4-dinitrophenol. Its structure was solved by X-ray diffraction; the crystal is monoclinic in space group P21/c. The morpholinium ring has a chair conformation with the CH2COO- substituent in the axial and the methyl group in the equatorial positions. The hydroxyl group of phenol and the carboxylate group of betaine are engaged in the O-H···O hydrogen bond of 2.471 Å.

The FTIR spectrum shows an intense broad absorption in the 1500-800 cm-1 region, characteristic for the short hydrogen bond.
The UV absorptions depend on the polarity of solvents used (DMSO, CH3CN). Two bands at ca. 310 and 425 nm suggest an equilibrium between the molecular complex and the hydrogen-bonded ion-pair in solution.
The optimized geometry of the complex investigated by the B3LYP/6-31G(d,p) approach is in a good agreement with the crystal structure. Linear correlations have been found between the experimental 1H and 13C chemical shifts and the magnetic isotropic shielding tensors computed by the GIAO/B3LYP/6-31G(d,p) method, which confirm the correct assignments of the proton and carbon chemical sfifts.

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Presentation: oral at 18th Conference on Physical Organic Chemistry, Symposium 2, by Zofia Dega-Szafran
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-05-05 11:12
Revised:   2009-06-07 00:44
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