title: Hydrogen bonding and dynamic behaviour in crystals and polymorphs of dicarboxylic-diamine adducts: a comparison between NMR parameters and X-ray diffraction studies.
abstract: Fumaric, malonic, maleic, and hydromuconic (HOOCCH2(CH)2CH2COOH) 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(muCH2CH2)3N] in various stoichiometric ratios. The resulting compounds have been investigated by using the 1H MAS, 15N, and 13C cross polarisation magic-angle spinning (CPMAS) methods and discussed in relation to X-ray diffraction studies to ascertain the nature of the O-HO, NH-O, and N+-HO- hydrogen bonds between the various species. In addition, two polymorphic forms of the malonic 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(muCH2CH2)3N] 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 1H spin-lattice relaxation times. A substantial agreement between the activation energies obtained from fitting the T1 data and the results of potential energy barrier calculations demonstrates that the facile reorientation of the [N(muCH2CH2)3N] molecule occurs in several of the adducts.
authors.affiliation: Dipartimento di Chimica I.F.M. Università di Torino, Via P. Giuria 7, 10125 Torino, Italy. roberto.gobetto@unito.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Gobetto
authors.forename: Carlo
authors.initials: C
authors.lastname: Nervi
authors.forename: Michele R
authors.initials: MR
authors.lastname: Chierotti
authors.forename: Dario
authors.initials: D
authors.lastname: Braga
authors.forename: Lucia
authors.initials: L
authors.lastname: Maini
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Grepioni
authors.forename: Robin K
authors.initials: RK
authors.lastname: Harris
authors.forename: Paul
authors.initials: P
authors.lastname: Hodgkinson