An X-ray and neutron diffraction investigation into engineering hydrogen bonding interactions in molecular complexes

The main focus of this research was to examine the molecular complexes formed by the proton sponge material DMAN [1,8-bis(dimethylamino)naphthalene]. It is well known that DMAN will readily protonate – forming the DMANH+ – leaving the second molecule in a DMAN complex negatively charged. In addition to the preparation of materials by crystallisation techniques, full characterisation was carried out using X-ray diffraction of the single crystal samples obtained. Neutron diffraction was also carried out on some of the samples for which the hydrogen atom information was most important to obtain, though this was restricted by the amount of beamtime available on the central facilities used. Several families of DMAN complexes were studied, including DMAN : benzoic acid (chapter 4), DMAN with a wide series of halo-substituted benzoic acids (Chapter 4), DMAN with hydroxyl-, nitro- and methyl- substituted benzoic acids (Chapter 5), and its complexes with a selection of other organic acids (Chapter 6). Several general patterns are found in this work, including the following: • The DMAN is usually protonated (DMANH+), with the hydrogen atom held in a short N−H···N intramolecular hydrogen bond, as observed previously; • The carboxylic acids tend to form dimers, but with a carboxyl and a deprotonated carboxylate group involved, these DIMER− units are formed through a single, very short, strong, charge-assisted O−H···O hydrogen bond; • a wide range of C−H···O and C−H···π weaker hydrogen bonds are present, together with consistent stacking of the DMAN rings, including π···π interactions, but with additional stacking at a range of interplanar distances; • the overall packing in several complexes includes chains or sheets of DIMER− units with DMANH+ included in pockets in the structure. There are some exceptions to these patterns, for example: • varying stoichiometry, resulting in the first example of the occurrence of both protonated (DMANH+) and unprotonated DMAN in a single complex • the inclusion of solvent water in some hydrated complex, which interrupts some of the patterns of intermolecular interactions In addition to the studies of DMAN, a ternary hydrogen bonded complex was studied using X-ray and neutron diffraction and the new molecular porous material 4-phenoxyphenol, containing a range of solvents, was fully characterised using these diffraction techniques as well as the thermal methods TGA and DSC.EThOS - Electronic Theses Online ServiceGBUnited Kingdo