3,5-Bis{3-[4-(dimethylamino)phenyl]prop-2-enylidene}-1-methyl-4-piperidone and 3,5-bis[3-(4-methoxyphenyl)prop-2-enylidene]-1-methyl-4-piperidone: potential biophotonic materials.

The structures of the title compounds, C(28)H(33)N(3)O, (I), and C(26)H(27)NO(3), (II), together with their two-photon absorption properties and fluorescence activities are reported. Molecules of (II) reside on crystallographic mirror planes containing the piperidone C=O group and N-methyl H atoms. Because of the conjugation between the donor and acceptor parts, the central heterocycle in both (I) and (II) exhibits a flattened boat conformation, with deviations of the N atom and the opposite C atom from the planar fragment. The dihedral angles between the coplanar heterocyclic atoms and terminal C(6) rings are less than 20 degrees in both (I) and (II). In (I), the N-methyl group of the ring occupies an equatorial position, but in (II) it is positioned in an axial site. In the crystal structure of (I), weak intermolecular C-H...pi(arene) and C-H...O steric contacts link the molecules along the a axis. In the crystal structure of (II), molecules form stacks along the b axis.