The title Schiff base, C14H11NO3, crystallizes as a zwitterion (i.e. proton transfer from the carb-oxy-lic acid group to the imine N atom). The dihedral angle between the aromatic rings is 19.59 (6)° and an intra-molecular N-H⋯O hydrogen bond closes an S(6) ring. In the crystal, inversion dimers linked by pairs of O-H⋯O hydrogen bonds generate R 2 (4)(24) loops. The dimers are linked by C-H⋯O i...

In the title zwitterion, C(7)H(14)N(2)O(3), the ethyl-amino and the 5-oxo groups are positionally disordered with occupancy ratios of 0.50:0.50 and 0.70:0.30, respectively. The terminal ethyl -CH(3) group undergoes considerable thermal motion. In the crystal, mol-ecules are linked via N-H⋯O hydrogen bonds, forming a two-dimensional arrangement propagating in the bc plane.

The title compound, C(7)H(13)N(5), a tetrazole analogue of betaines, exists as a zwitterion, with the H atom of the tetrazole ring being transferred to the piperidine ring N atom. The tetrazole ring symmetry is close to C(2v), which suggests strong charge delocalization in the N-C-N fragment of the ring. There are classical hydrogen bonds in the structure which are responsible for the formation...

The title compound, C(6)H(5)NO(2)·C(6)H(6)O(2), crystallizes with one pyridinium-2-carboxyl-ate zwitterion and one mol-ecule of benzene-1,2-diol in the asymmetric unit. The crystal structure is characterized by alternating mol-ecules forming zigzag chains running along the a axis: the mol-ecules are connected by O-H⋯O and N-H⋯(O,O) hydrogen bonds.

In the methanol solvate of the title 1:1 cocrystal, C(29)H(28)F(6)N(4)OS·C(5)H(9)NO(2)·CH(4)O, the l-proline mol-ecule exists as a zwitterion. In the crystal, the disubstituted thio-urea, l-proline and methanol mol-ecules are linked by N-H⋯O and N-H⋯N hydrogen bonds, forming a two-dimensional array in the ab plane.

The title compound, C(6)H(11)N(3)O(2), is a cyclized derivative of l-arginine and the mol-ecule is a zwitterion with the positive and negative charge residing in the guanidinium and carboxyl-ate groups, respectively. The conformation of 1,3-diazepane ring is close to a twisted chair. One intra-molecular and three inter-molecular N-H⋯O hydrogen bonds stabilize the mol-ecular conformation and the...

In the crystal of the title compound, C23H17Cl2NO2, the H atom of the -OH group is transferred to the N atom of the imine, forming a zwitterion. This results in a six-membered intra-molecular O⋯H-N hydrogen-bonded ring, rather than that formed with an O-H⋯N hydrogen bond. The dihedral angle between the rings of the biphenyl unit is 13.88 (10)°. In the crystal, mol-ecules are linked by N-H⋯O and...

In the title compound, C(4)H(4)N(2)O(2), both imidazole N atoms are protonated and carboxyl-ate group is deprotonated, resulting in a zwitterion. The mol-ecule is essentially planar, with an r.m.s. deviation of 0.012 (1) Å. In the crystal, N-H⋯O hydrogen bonds and π-π stacking inter-actions [centroid-centroid distance = 3.674 (2) Å] between the imidazole rings link the mol-ecules into a three-d...

The title compound, C(6)H(8)NO(3)P, is isostructural with p-arsanilic acid. It exists as the zwitterion H(3)N(+)C(6)H(4)PO(3)H(-). In the crystal, mol-ecules are linked by O-H⋯O and N-H⋯O hydrogen-bond bridges, giving a three-dimensional network structure. The strongest hydrogen bonds are formed between adjacent PO(3)H groups with O⋯O distances of 2.577 (2) Å.