New crystal structure of molecular complex 1-piperidine carboxylate-piperidinium-H2O studied by X-ray single crystal diffraction

Piperidine absorbs CO₂ and H₂O in air to form a molecular complex: piperidium-1-piperidinecarboxylate-H₂O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was determined to be triclinic, space group P with a=0.648 6(8) nm, b=0.809 2(10) nm, c=1.357 1(16) nm, α=96.967(16)°, β=102.506(15)°,, γ=104.202 (15)°, Z=2. The complex is stabilized via five hydrogen bonds between the three components, N—O electrostatic interaction and O—O interaction (electron transfer) between1-piperidinecarboxylate and H₂O. Due to electron transference of carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O—H bond is considerably shorter than that of the free molecule of water. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein. Biography: JIANG Huiming (1972–), male, Associate professor, research direction: molecular complex chemistry, supramolecular chemistry.