Three new quinuclidine-based structures: second harmonic generation response for...

The crystal structures of three quinuclidine-based compounds, namely (1-azabicyclo[2.2.2]octan-3-ylidene)hydrazine monohydrate, C₇H₁₃N₃·H₂O (1), 1,2-bis(1-azabicyclo[2.2.2]octan-3-ylidene)hydrazine, C₁₄H₂₂N₄ (2), and 1,2-bis(1-azoniabicyclo[2.2.2]octan-3-ylidene)hydrazine dichloride, C₁₄H₂₄N₄²⁺·2Cl^- (3), are reported. In the crystal structure of 1, the quinuclidine-substituted hydrazine and water molecules are linked through N-H...O and O-H...N hydrogen bonds, forming a two-dimensional array. The compound crystallizes in the centrosymmetric space group P2₁/c. Compound 2 was refined in the space group Pccn and exhibits no hydrogen bonding. However, its hydrochloride form 3 crystallizes in the noncentrosymmetric space group Pc. It shows a three-dimensional network structure via intermolecular hydrogen bonding (N-H...C and N/C-H...Cl). Compound 3, with its acentric structure, shows strong second harmonic activity.