Crystal structure and phase transitions in N-benzyl piperidinium dihydrogenmonophosphate, C6H5CH2CHCH2CH2NH2CH2CH2 center dot H2PO4

The salt N-benzyl piperidinium dihydrogenmonophosphate (N-BPP) is orthorhom bic P2(1)2(1)2(1) with the following unit cell dimensions: a = 6.044(1) Ang strom, b = 9.038(1)Angstrom, c = 25.126(3)Angstrom, D-m = 1.302 Mg m(-3), D -x = 1.322 Mg m(-3), mu = 0.21 mm(-1), F(000) = 584; T = 298 K; R = 0.045, and R-w = 0.138 for 1721 independent reflections, The structure consists of infinite parallel two-dimensional planes built of mutually H2PO4- anions a nd [C6H5CH2CHCH2CH2NH2CH2CH2] + cations connected by strong O-H . . .O and N-H . . .O hydrogen bonding. There are no contacts other than normal van de r 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 r evealed a second-order phase transition at 269 K, The Raman and infrared of polycrystalline samples of N-BPP have been recorded at different temperatu res between 170 and 435 K. (C) 2000 Academic Press.