Hydrogen bonding and dynamic behaviour in crystals and polymorphs of dicarboxylic-diamine adducts: A comparison between NMR parameters and X-ray diffraction studies

Fumaric, malonic, maleic, and hydromuconic (HOOCCH2(CH)(2)CH2COOH) acids were used to prepare a series of hydrogen-bonded adducts or salts, depending on whether acid-base proton transfer takes place, with the dibase [N-(mu CH2CH2)(3)N] in various stoichiometric ratios. The resulting compounds have been investigated by using the H-1 MAS, N-15, and C-13 cross polarisation magic-angle spinning (CPMAS) methods and discussed in relation to X-ray diffraction studies to ascertain the nature of the O-(HO)-O-..., (NH)-H-...-O, and N+-(HO)-O-...-hydrogen bonds between the various species. In addition, two polymorphic forms of the nialonic compound and a hydrate in the maleic case were examined. We also present the correlations between the chemical shifts of the hydrogen-bonded protons and those from the proton transfer reaction (acid-to-base) with the heavy atom distances. The dynamic behaviour in the solid-state of the [N-( mu CH2C2)(3)N adducts with fumaric 2:1, maleic 1:1 hydrate, and hydromuconic acids, and a malonate 2:1 polymorph adduct have been investigated by using variable-temperature H-1 spinlattice relaxation times. A substantial agreement between the activation energies obtained from fitting the T-1 data and the results of potential energy barrier calculations demonstrates that the facile reorientation of the [N-(mu CH2CH2)(3)N] molecule occurs in several of the adducts.