Bis(N-methylpiperidine betaine) hydrobromide: crystal structure and hydrogen bonding

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].…”

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

“…[22] Similar symmetric hydrogen-bonded dimers exist in type A acid salts of monocarboxylic acids, for example, (RCOO) 2 HK. [23] Homoconjugated cations with symmetric OÁÁÁHÁÁÁO hydrogen bonds were found in several structures of betaines, for example, bis(betaine) hydrochloride monohydrate, [24] bis(betaine)nitrate, [25] bis(homarine)hydrogen perchlorate, [26] bis(N-methylpiperidine betaine) hydrobromide, [27] bis(N-methylpiperidine betaine) hydroiodide, [28] and bis(N-methylpiperidine betaine) hydrochloride. [29] Very short OÁÁÁHÁÁÁO hydrogen bonds were also found in hydrogen squarate derivatives.…”

“…[30,31] However, the OÁÁÁHÁÁÁO hydrogen bond in the investigated compound is by 0.009-0.011 Å shorter than in bis(N-methylpiperidine betaine) hydrohalides, (MPB) 2 HX. [27][28][29] The B iso displacement parameter of the H atom in the OÁÁÁHÁÁÁO bridge [8.4(10) Å 2 ] is higher than the component of the B aniso tensor of the terminal O atoms along the OÁÁÁO line [1.58(4) Å 2 ], indicating that although this hydrogen bond is crystallographically centrosymmetric, the proton may be distributed either dynamically or statically on both sides of the inversion center. However, with an OÁÁÁO distance of 2.436(2) Å , its expected deviation from the midpoint of the OÁÁÁO vector is small, about 0.09 Å .…”

“…Symmetry operation for the generation of the second half of the (MPBu) 2 H þ dimer: À1Àx, 2Ày, 1Àz -CH 2 CH 2 CH 2 COO À substituent is in the axial position and is linked by the OÁÁÁHÁÁÁO hydrogen bond with its centrosymmetric copy within the dimeric (MPBu) 2 H þ cation. It is of note that in (MPB) 2 HX complexes [27][28][29] the -CH 2 COO À group is in the equatorial position, while in the 1:1 complexes the -(CH 2 ) n COO À substituent has been also found in the axial position, for example, in 4-(N-methylpiperidinium)-butyric acid bromide, [33] N-methylpiperidine betaine hydrochloride, [34] and hydrobromide. [35] Both positions of the -CH 2 COO À substituent are observed in complexes of MPB with hexafluorosilicic acid [36,37] and tartaric acid.…”

Unusual aggregation of bis(2-quinuclidinium-butyrate) hydrobromides

“…The center of gravity of this absorption, m H , calculated for the 1500-400 cm À1 region, from the ratio of P Am/ P m, is around 900 cm À1 . A similar broad absorption is present in the IR spectra of 2:1 complexes of other betaines with acids [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] and of type A acid salts of carboxylic acid [3,57]. Notable is the absence of any distinct absorption in the region above 1800 cm À1 , except for the stretching CH 3 , CH 2 and C-H vibrations, which are also observed in the spectrum of QNBuÁH 2 OÁHBr [39].…”