The crystal structure of zwitterionic 2-{[(4-iminiumyl-3-methyl-1,4-dihydropyridin-1-yl)methyl]carbamoyl}benzoate hemihydrate

Abstract

The asymmetric unit of the title compound, C 15 H 15 N 3 O 3 Á0.5H 2 O, comprises two 2-{[(4-iminiumyl-3-methyl-1,4-dihydropyridin-1-yl)methyl]carbamoyl}benzoate zwitterions (A and B) and a water molecule. The dihedral angles between the pyridine and phenyl rings in the zwitterions are 53.69 (10) and 73.56 (11) in A and B, respectively. In the crystal, molecules are linked by N-HÁ Á ÁO, O-HÁ Á ÁO, C-HÁ Á ÁO and C-HÁ Á Á (ring) hydrogen bonds into a three-dimensional network. The crystal structure also features -interactions involving the centroids of the pyridine and phenyl rings [centroid-centroid distances = 3.5618 (12) Å in A and 3.8182 (14) Å in B]. Chemical contextZwitterions are high-performance materials that can be used as drug protein stabilizers without affecting the activity of the drug (Keefe & Jiang, 2012). Drug protein stabilizers not only maintain the native chemical structure, but the native secondary and higher order structures necessary for biological activity and can increase the stability of the therapeutic protein and enhancs protein-substrate hydrophobic interactions without affecting the activity of the drugs. Zwitterionic polymers grafted from polysulfone (PSF) membranes show improved protein anti-fouling properties, together with good blood compatibility and cytocompatibility in comparison with the pristine PSF membrane (Yue et al., 2013). Furthermore, zwitterionic nanocarrier drugs showed excellent biocompatibility and non-fouling properties, and were found to extend blood circulation times in vivo. The study and synthesis of new zwitterions is therefore important in the search for new biomedical applications (Jin et al., 2014). Structural commentaryThe asymmetric unit of the title compound comprises two crystallographically independent 2-{[(4-iminiumyl-3-methyl-1,4-dihydropyridin-1-yl)methyl]carbamoyl}benzoate zwitterions (molecules A and B) and a cocrystallized water molecule, as shown in Fig. 1. The zwitterions are formed through protonation of the imine substituent on the pyridine ring and deprotonation of the carboxylate substituent on the benzene ring. The bond lengths and angles (Table 1) Supramolecular featuresIn the crystal, molecules are linked by N-HÁ Á ÁO, C-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds (Table 2) The molecular structure of the title compound, with the atom labelling and 50% probability displacement ellipsoids. Figure 2A partial packing diagram, with an R 2 4 (8) ring motif generated by N-HÁ Á ÁO hydrogen bonds (dotted lines). Hydrogen-bond geometry (Å , ).Cg1 and Cg2 are the centroids of the C9B-C14B and N1B/C1B-C5B rings, respectively. dimensional network. Intermolecular N3A-H1N3Á Á ÁO3A, N3A-H2N3Á Á ÁO3B, N3B-H3N3Á Á ÁO3A and N3B-H4N3Á Á ÁO3B hydrogen bonds generate R 2 4 (8) ring motifs (Fig. 2), while N2A-H2N2Á Á ÁO2B and N2B-H1N2Á Á ÁO2A hydrogen bonds form dimers with R 2 2 (14) ring motifs (Fig. 3). Molecule A is connected to molecule B through a C2A-H2AAÁ Á ÁCg1 interaction, while molecules of B are linked by C11B-H11BÁ Á ÁCg2 interactions (Cg1 and Cg2 ar...