Structural studies of organic and organometallic compounds using x-ray and neutron techniques

Abstract

This thesis is sub-divided into two parts. Part (i) is entitled 'Structure / Property Relationships in Non-linear Optical Materials' (chapters 1-8) whilst part (ii) is entitled 'Structural Studies of imido, (bis)imido and aryloxide group VA and VIA transition metal complexes' (chapters 9-10).Chapters 1, 2 and 3 provide an introduction to non-linear optics, X-ray and neutron experimental techniques used in this thesis and charge density studies respectively. Chapters 4 to 8 describe the investigations of the part (i) topic. These include bond length alternation studies on a series of tetracyanoquinodimethane derivatives and a charge density study of one of these compounds in chapter 4. Several other charge density studies are reported in chapters 5 and 6 which concentrate on methyl- nitropyridine and nitroaniline derivatives and the compound, 3-( 1,1 -dicyanoethenyl)-l-phenyl-4,5- dihydro-1 H-pyrazole (DCNP) respectively. Chapter 5 also deals with the effect of intermolecular interactions on the non-linear optical phenomenon whilst in chapter 6, a detailed analysis of the thermal motion present in DCNP is also given. Investigations on intermolecular interactions are also reported in chapters 7 and 8 which studies the compounds, N-methylurea and zinc(tris)thiourea sulphate respectively. In the former case, the neutron derived structure of N-methylurea is reported at two temperatures and it is revealed that disorder is present at the higher temperature. In the latter case, neutron results from an instrument presently in the testing stages of its development are reported and contrasted with those obtained using a well established instrument. Chapters 9 and 10 describe the investigations of the part (ii) topic. These concentrate on the structural features of two series of organometallic compounds which have potential use as polymerization catalysts. Relationships between structure and reactivity are reported.