Structural, spectroscopic, and theoretical studies of a very short OHO hydrogen bond in bis(4‐(N‐methylpiperidinium)‐butyrate) hydrobromide

Abstract

The molecular structure of bis(4-(N-methylpiperidinium)-butyrate) hydrobromide, (MPBu) 2 HBr, has been characterized by single crystal X-ray diffraction, infrared and NMR spectroscopies, and by DFT calculations. The crystals of the title compound at 140 K are monoclinic, space group C2/c, with a ¼ 11.7118 (4)and Z ¼ 4. Two 4-(N-methylpiperidinium)-butyrate moieties are joined by a very short and centrosymmetric O.H.O hydrogen bond of 2.436(2) Å . The piperidine ring adopts a chair conformation with the methyl group in the equatorial and the bulky -(CH 2 ) 3 COO substituent in the axial position. The broad absorption band below 1500 cm S1 in the FTIR spectrum confirms the existence of a very short O . H . O hydrogen bond. The 1 H and 13 C NMR spectra are interpreted on the basis of 2D experiments and the calculated GIAO/B3LYP/6-31G(d,p) magnetic isotropic shielding tensors. In the optimized structure of the complex, a 4-(N-methylpiperidinium)-butyrate zwitterion interacts with a 4-(N-methylpiperidinium)-butyric acid cation forming an O . . . H-O hydrogen bond of 2.580 Å .

Unusual 2:3:2 complex of DABCO mono-betaine with HCl and H2O studied by X-ray diffraction, DFT calculations and spectroscopic methods

“…The center of gravity, of this absorption, m H , is at 985 cm À1 . A similar absorption is observed in the spectra of the acid-salts of carboxylic acids [1] and basic salts of betaines [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”