Crystal Structure and Phase Transitions in N-benzyl Piperidinium Dihydrogenmonophosphate, C6H5CH2CHCH2CH2NH2CH2CH2·H2PO4

The salt N-benzyl piperidinium dihydrogenmonophosphate (N-BPP) is orthorhombic P212121 with the following unit cell dimensions: a=6.044(1) ?, b=9.038(1) ?, c=25.126(3) ?, Dm=1.302 Mgm-3, Dx=1.322 Mgm-3, MU=0.21 mm-1, F(000)= 584; T=298 K; R=0.045, and Rw=0.138 for 1721 independent reflections. The structure consists of infinite parallel twodimensional planes built of mutually H2PO-4 anions and [C6H5CH2CHCH2CH2NH2CH2CH2]+ cations connected by strong O–H···O and N–H···O hydrogen bonding. There are no contacts other than normal van der Waals interactions between the layers. Differential scanning calorimetry study on N-BPP was carried out. A low-temperature phase transition at 269 K to an ordered phase was found. Measurements by the electric permittivity revealed a second-order phase transition at 269 K. The Raman and infrared of polycrystalline samples of N-BPP have been recorded at different temperatures between 170 and 435 K.