Structure of co-crystal of N-methylpiperidine betaine–l(+)-tartaric acid

N-Methylpiperidine betaine (MPB) and l(+)-tartaric acid form a six-molecular non-centrosymmetric crystalline complex through two OH⋯OC and four COO⋯HOOC hydrogen bonds. The structure of this co-crystal has been determined by X-ray diffraction. The molecular structure of the title compound has been studied by FTIR, Raman and NMR spectroscopies and calculations by the B3LYP/3-31G(d,p) level of theory. This co-crystal belongs to the monoclinic system, space group P21 with a = 10.2691(4), b = 9.4528(3), c = 24.0637(7) Å, β = 98.227(3)°, Z = 2, R = 0.026. Two molecules of TA and four molecules of MPB form a six-membered, asymmetric, hydrogen-bonded cluster, [(MBP)2TA]2. The core of the cluster is formed by two TA molecules linked by OH⋯OC hydrogen bonds of the lengths 2.786(1) and 2.761(1) Å, into a cyclic asymmetric dimer. Four MPB molecules are bonded to the TA core by four COO⋯HOOC hydrogen bonds of the lengths 2.493(1), 2.496(1), 2.511(1) and 2.512(1) Å. The piperidine ring has a chair conformation, however, the CH2COO− substituent at the nitrogen atom occupies the opposite positions (axial and equatorial) in MPB moieties bonded to each TA. The clusters are bonded into infinite chains, parallel to the y-axis, by the OH⋯OC hydrogen bonds of 3.051(1) Å. In the optimized structure of the title complex the fragments of (MPB)2TA in the cluster are twisted, which causes a shortening of the intermolecular hydrogen bonds between the TA molecules. The FTIR spectrum is consistent with the X-ray structure.