Weak intermolecular interactions in organic systems: a concerted study involving x-ray and neutron diffraction and database analysis

Abstract

This thesis can be divided broadly into two halves. The first half (Chapters 3 - 5) deals with crystallographic studies of compounds which contain weak intermolecular interactions or networks of these interactions. Whilst the later part (Chapters 7 - 9) describes the results of database surveys of three novel weak intermolecular interactions. In Chapters 3 and 4 the neutron derived structures of 3,5-dinitrocinnamic acid, 2-ethynyladamantan-2-ol, 2- and 3-ammophenol are presented. All of the compounds contain complex networks of weak hydrogen bonds. The neuron diffraction data are used to determine accurate hydrogen atom poistions and thus characterise these hydrogen bonded networks. Some theoretical work is also described. In Chapter 5, X-ray diffraction studies of a series of iodobenzene derivatives are described. These compounds were synthesised in an attempt to engineer structures mediated by novel X...O(_2)N interactions. The structures of three iodo nitrobenzenes are presented wherein symmetrical bifurcated I...O(_2)N interactions mediate the primary ribbon motif. The structure of TCNQ derivative, in which I...N=C play a structure determining role, is also described. Chapters 7, 8 and 9 describe database smdies of X...O(_2)N, C(ring)-H...O/N and C-F...H interactions. The frequencies and geometries of the interactions were determined and analysed. The data for X...O(_2)N interactions were used in conjunction with sophisticated IMPT calculations to determine prefered interaction geometries and interaction energies. Similar theoretical techniques were used to analyse the C(ring)-H...O/N and C-F..H interactions described in Chapters 8 and 9.Background information and overviews of the general experimental procedures followed when performing the crystallographic and database studies are given in Chapters 2 and 6.