3,5-Bis(4-methoxybenzylidene)-1-methyl-4-piperidone and 3,5-bis(4-methoxybenzylidene)-1-methyl-4-oxopiperidinium chloride: potential biophotonic materials.

In the title compound 3,5-bis(4-methoxybenzylidene)-1-methyl-4-piperidone, C(22)H(23)NO(3), (I), the central heterocyclic ring adopts a flattened boat conformation, while in the related salt 3,5-bis(4-methoxybenzylidene)-1-methyl-4-oxopiperidinium chloride, C(22)H(24)NO(3)(+).Cl(-), (II), the ring exhibits a 'sofa' conformation in which the N atom deviates from the planar fragment. The pendant benzene rings are twisted from the heterocyclic ring planes in both molecules in the same direction, the range of dihedral angles between the ring planes being 24.5 (2)-32.7 (2) degrees . The dominant packing motif in (I) involves centrosymmetric dimers bound by weak intermolecular C-H...O hydrogen bonds. In (II), cations and anions are linked by strong N-H...Cl hydrogen bonds, while weak C-H...O and C-H...Cl hydrogen bonds link the cations and anions into a three-dimensional framework.