In the crystal structure of the title compound, C(16)H(12)O(2), no classical hydrogen bonds or aromatic π-π stacking inter-actions were observed. The mol-ecules are linked into a three-dimensional framework by a combination of C-H⋯O and C-H⋯π(arene) hydrogen bonds.

Amide-attached pyrrole-based π-conjugated anion receptors showed solvent-dependent assembled modes such as H-aggregates that were soluble in octane and highly organized structures that provided supramolecular gels in CH(2)Cl(2) and 1,4-dioxane in the absence of π-π stacking.

The title compound, C(11)H(10)ClNO, is close to being planar (r.m.s deviation for the non-H atoms = 0.026 Å). In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, generating C(2) chains, and weak C-H⋯π inter-actions and aromatic π-π stacking inter-actions [centroid-centroid distance = 3.713 (3) Å] help to consolidate the structure.

Apart from the methyl group of the meth-oxy fragment, the title compound, C(15)H(12)N(2)O, is almost planar (r.m.s. deviation = 0.045 Å); the C atom deviates from the mean plane by 1.216 (1) Å. In the crystal, π-π stacking [shortest centroid-centroid separation = 3.4652 (10) Å] and C-H⋯π inter-actions occur.

The title compound, C(17)H(14)ClN(7), crystallizes with two independent mol-ecules in the asymmetric unit. Inter-molecular N-H⋯N and C-H⋯N hydrogen bonds contribute to the stability of the crystal structure. In addition, weak C-H⋯π and π-π stacking [centroid-centroid distances of 3.699 (8) and 3.699 (6) Å] interactions are observed.

The asymmetric unit of the title compound, C(16)H(14)N(2), contains two independent mol-ecules in which the dihedral angles between the pyrimidine and naphthaline rings are 38.20 (5) and 39.35 (5)°. Inter-molecular C-H⋯π contacts and π-π stacking inter-actions [centroid-centroid distances = 3.766 (1) and 3.792 (1) Å] are present in the crystal structure.

In the title compound, C(16)H(12)N(2), the dihedral angle between the indole ring system and the pendant phenyl ring is 64.92 (5)°. The crystal packing features aromatic π-π stacking [centroid-centroid separation = 3.9504 (9) Å] and C-H⋯π inter-actions.

The title compound, C(23)H(20)N(4)O, is a heterocyclic phenyl-hydrazone Schiff base with a pyrazole moiety. In the crystal, a variety of inter-actions occur, including N-H⋯π and π-π stacking between the phenyl ring of the phenyl-hydrazinyl group and its symmetry-generated equivalent [centroid-centroid distance = 3.6512 (7) Å].

The title compound, C(12)H(15)ClN(2)O, is a piperazine derivative with the potential for use as a starting material for pharmaceutial and agrochemical applications. The structure is stabilized by C-H⋯O hydrogen bonds, C-H⋯π inter-actions and π-π stacking inter-actions [centroid-centroid distance = is 4.760 (2) Å].

In the title compound, C(17)H(14)N(2)O, the dihedral angle between the indole ring system and the benzene ring is 58.41 (4)°. The crystal packing features π-π stacking [shortest centroid-centroid separation = 3.8040 (9) Å] and C-H⋯π inter-actions.