4-(2-Carb-oxy-vin-yl)pyridinium iodide.

In the crystal structure of the title salt, C(8)H(8)NO(2) (+)·I(-), the cations and anions are linked by bifurcated N-H⋯(O,I) hydrogen bonds. A near-linear O-H⋯I hydrogen bond also exists between the cation and anion, resulting in a two-dimensional network. In the cation, the carboxyl group is twisted with respect to the pyridine ring at a dihedral angle of 15.34 (17)°.

5-p-Tolyl-1H-tetra-zole.

The title compound, C(8)H(8)N(4), possesses crystallographic mirror symmetry, with four C atoms lying on the reflecting plane, which bis-ects the phenyl and tetra-zole rings. It is composed of a planar r.m.s. deviation (0.0012 Å) tetra-zole ring which is nearly coplanar with the benzene ring, the dihedral angle being 2.67 (9)°. In the crystal, symmetry-related mol-ecules are linked by inter-molecular N-H⋯N hydrogen bonds. The mol-ecules stack along [100] with a π⋯π inter-action involving the phenyl and tetra-zole rings of adjacent mol-ecules [centroid-centroid distance = 3.5639 (15) Å]. The H atom of the N-H group is disordered over two sites of equal occupancy. The methyl H atoms were modelled as disordered over two sets of sites of equal occupancy rotated by 60° with respect to each other.

1-(3-Amino-1H-inden-2-yl)ethanone.

The title compound, C(11)H(11)NO, was synthesized by the reaction of 2-(bromo-meth-yl)benzonitrile and acetyl-acetone in the presence of KOH. In the crystal packing, mol-ecules are linked by inter-molecular N-H⋯O hydrogen bonds into chains running parallel to the b axis. Centrosymmetrically-related chains inter-act further through weak C-H⋯π inter-actions.