Two non-equivalent complexes of 1-piperidineacetic acid with 2,4-dinitrophenol studied by X-ray diffraction, PM3 and SAM1 methods and FTIR

Crystal structure of the complex of 1-piperidineacetic acid (PAA) with 2,4-dinitrophenol (24DNP) has been solved by X-ray diffraction. The crystals are triclinic, space group Pı¯ with a ¼ 7:178ð1Þ A ° , b ¼ 11:746ð2Þ A ° , c ¼ 18:118ð4Þ A ° , a ¼ 84:42ð3Þ8; b ¼ 83; 34ð3Þ8; g ¼ 86:36ð3Þ8; Z ¼ 4; R ¼ 0:0563: PAA forms with 24DNP two non-equivalent complexes through O· · ·H–O hydrogen bonds of the different lengths (2.500(3) and 2.431(3) A° ). Each of these complexes forms a centrosymmetric dimer, denoted as A and B, in which two PAA moieties are joined by two N–H· · ·O hydrogen bonds (2.875(3) and 2.797(3) A ° ) around two different symmetry centers. The C–H· · ·O contacts consolidate the structure in the unit cell. The structures optimized by the PM3 and SAM1 methods also reproduce two dimers A and B whose energies, dipole moments and their geometries are slightly different. The FTIR spectrum confirms the presence of the N–H· · ·O and O–H· · ·O hydrogen bonds. q 2004 Elsevier B.V. All rights reserved.