The crystal structures of Ni(NCS)₂(4-ViPy)₂.nG where nG = 2CH₂Cl₂ (I), 2CCl₄ (II), 1.8CH₂I₂ (III) and CHI₃ (IV), as well as the crystal structure of [Ni(NCS)₂(4-ViPy)₄]. [Ni(NCS)₂(4-ViPy)₃(thf)].2CHI₃ (V) have been elucidated. The diiodomethane guest molecules in STRUCTURE III were severely disordered at room temperature and so this structure was solved at -40°C. The dichloromethane clathrate is isomorphous with the chloroform clathrate of the same host, and both these clathrates have a similar packing to the carbon tetrachloride clathrate. There is significant secondary bonding between the sulphur (donor) of the isothiocyanate ligand of the host and the iodines (acceptor) of the halogenated guest molecules in compounds III, IV and V. The iodoform clathrates, compounds IV and V, also show strong similarities in their packings. Particular attention has been paid to the shape and size of the cavities in which the guest molecules find themselves, in order to gain a better understanding of the nature of these clathrates. This has also shed some light on the probable cause of the disordered diiodomethane molecules in STRUCTURE III. Packing densities and volume comparisons of the [Ni(NCS)₂(4-ViPy)₂] clathrates have been carried out. Solid - state U.V/visible spectroscopy was used to obtain information on the host conformation, and thermal analysis (thermogravimatry and differential thermal analysis) was used to obtain insight into the host - guest interactions of these clathrates.

The aim of this thesis is to develop a set of intermolecular potentials that enable the study of nucleation or decomposition of methane hydrates. The potentials are developed for water, methane, and the water-methane pair by fitting to SAPT(DFT) reference energies. The first set of potentials developed differ from recent polarisable models in that they have rank 4 ISA multipoles, rank 3 anisotropic polarisabilities, rank 3 isotropic dispersion, and anisotropic exchange-repulsion terms. These potentials are validated based on the structures and energies of small clusters and second virial coefficients. The potentials are then significantly simplified for use in MD simulations with DL_POLY4. Simplifying the methane potential makes it difficult to fit simultaneously the global minimum dimer and a set of randomly generated dimers used as reference energies. Several methods are tested to account for polarisation in water within the limitations of DL_POLY and it is found that for MD simulations good results can be attained by increasing the charge values to match the multipole moments of a water molecule in a dielectric. Simulations are carried out for liquid water, ice Ih, and methane gas to validate the new models. The models developed are compared in MD simulations with TIP4P/Ice and the United Atom Methane (UAM) model in simulations of sI methane clathrate; both under stable conditions and while undergoing decomposition at different temperatures. It is found that the melting behaviour differs according the methane- and water-methane interactions; the behaviour of methane under clathrate decomposition using either methane model is discussed.

Thesis (Ph. D.)--Dept. of Physical and Inorganic Chemistry, University of Adelaide, 1986. / Includes bibliographical references (leaf 179).

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 157-169). Also available on the World Wide Web.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2009 / The host compound 9-(4-methoxyphenyl)-9H-xanthen-9-01 (AI) forms inclusion compounds with the solid guests l -naphthylamine (NAPH), 8-hydroxyquinoline (HQ). acridine (ACRI), 1,4 - diazabicyclo[2.2.2]octane (DABCO) and a liquid guest benzaldehyde (BENZAL). All four structures AI·YzNAPH, AI· Y,HQ AI·ACRI and AI ·Y,DABCO were successfully solved in the triclinic space group P I . The structure of AI·Y,BENZAL was successfully solved in the monocl inic space group P2dn . Similar packin g motifs arise for the NAPH and HQ inclusion compounds where the main interaction is of the fonm (Host)-OH····O-(Host). Both the DABCO and the ACRI guests hydrogen bond to the host molecule. The host: guest ratios for A I·ACRI. AI· Y,NAPH. A I· Y,DABCO and A I· YzHQ were found using nuclear magnetic resonance (NMR) spectroscopy. The host:guest ratio for AI·YzBENZAL was found using thenmogravimetric analysis. Enthalpy changes of the inclusion compounds were monitored using differential scanning calorimetry (DSC). Kinetics of desolvation for AI·Y,BENZAL were conducted using a non - isothenmal method where we have obtained an activation energy range of 74 k J morl - 86 k J mor' . The solid - solid reaction kinetics for A I·Y,NAPH, A I· Y,HQ, AI·ACRI and AI ·Y,DABCO were determined at room temperature using powder X-ray diffraction (PXRD).

by Qi Li. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 192-199). / Acknowledgment --- p.i / Abstract --- p.ii / Table of Contents --- p.iii / Index of Componds --- p.iv / List of Tables --- p.v / List of Figures --- p.vi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- General Survey of Inclusion Chemistry --- p.1 / Chapter 1.2. --- The Importance of Hydrogen Bonds --- p.5 / Chapter 1.3. --- "Classical Inclusion Compounds of Urea, Thiourea and Selenourea" --- p.8 / Chapter 1.4. --- Research Strategy --- p.12 / Chapter 2. --- Description of Crystal Structures --- p.16 / Chapter 2.1. --- Urea-Anion Inclusion Compounds --- p.16 / Chapter 2.1.1. --- Halide complexes --- p.18 / Chapter 2.1.2. --- Bicarbonate complexes --- p.30 / Chapter 2.1.3. --- Allophanate complexes --- p.36 / Chapter 2.1.4. --- Borate and pentaborate complexes --- p.44 / Chapter 2.1.5. --- Complex featuring both host-host and host-guest hydrogen bonding --- p.60 / Chapter 2.1.6. --- Tetraethylammonium and phosphonium chloride complexes --- p.65 / Chapter 2.2. --- Thiourea-Anion Inclusion Compounds --- p.71 / Chapter 2.2.1. --- Halide Complexes --- p.73 / Chapter 2.2.2. --- Bicarbonate Complexes --- p.76 / Chapter 2.2.3. --- Nitrate Complexes --- p.87 / Chapter 2.2.4. --- Formate Complexes --- p.101 / Chapter 2.2.5. --- Acetate Complexes --- p.113 / Chapter 2.2.6. --- Oxalate and Fumarate Complexes --- p.127 / Chapter 2.2.7. --- Unsymmetrical quaternary ammonium ions as guests --- p.138 / Chapter 2.3. --- Selenourea-Anion Inclusion Compounds --- p.152 / Chapter 3. --- Summary and Discussion --- p.161 / Chapter 3.1. --- Structural Features and Relationships --- p.161 / Chapter 3.2. --- Hydrogen Bonding in Urea/Thiourea/Selenourea-Anion Inclusion Compounds --- p.164 / Chapter 3.3. --- Linkage Modes of Urea and Thiourea Molecules --- p.168 / Chapter 3.4. --- Comolecular Aggregates of Urea and Other Host Components --- p.173 / Chapter 3.5. --- Comolecular Aggregates of Thiourea and Other Host Components --- p.175 / Chapter 4. --- Experimental --- p.177 / Chapter 4.1. --- Preparation --- p.177 / Chapter 4.2. --- Crystallography --- p.182 / Chapter 5. --- References --- p.192 / Appendix A: Tables of Atomic coordinates and thermal parameters --- p.200 / Appendix B: Publication Based on Results Reported in This Thesis --- p.243

Investigation on a series of hydrogen-bonded networks constructed with N-heteroaryl acids is described in Section 3.4. In this section, we focused on the connection modes within the heteroaryl dimer. The study of co-crystals and inclusion compounds based on 2-thiobarbituric acid (TBA) or trithiocyanuric acid (TCA) indicated that the dimer of TBA is present in all three crystals in the forms of ribbon, tetramer or separated dimer. In the case of 5-nitrobarbiturate, its dimer occurs in two ammonium salts and in three of its four thiourea complexes, but is absent in all three urea complexes. / Self-assembly of two-dimensional hydrogen-bonded honeycomb grids exhibiting the rosette motif has been conducted with the guanidinium cation and various anions as the building blocks, tetraalkylammonium ions of suitable bulk being employed as interlayer templates. It is noteworthy that the rosette layer constructed from three different trigonal-planar molecular components has been achieved. In addition, deviating from conventional topological design, the generation of new rosette layers, albeit highly distorted, has also been accomplished with 1,2-dithiosquarate and the dianionic form of 1,1'-biphenyl-2,2',6,6'-tetracarboxylate that do not conform to C3-symmetry. Although threefold molecular symmetry is regarded as a sacrosanct requirement for molecular building blocks in the construction of hydrogen-bonded rosette motif, this study shows that rosette motifs can be generated even if one of the building blocks does not have inherent threefold symmetry. / Study of compounds containing the deprotonated forms of Kemp's triacid (H3KTA) has revealed the chair or twist-boat conformation in six crystal structures. X-ray structural analysis showed that [C(NH2) 3+] · [C6H6(CH3) 3(COOH)2(COO-)] (2.2.2) exhibits a corrugated layer structure which mimics the rosette motif constructed from the guanidinium ion and the hydrogen carbonate dimer. The tricarboxylate form of Kemp's triacid KTA3- in 3[C(NH2) 3+] · [C6H6(CH3) 3(COO-)3] (2.2.4) registers a record number of eighteen acceptor hydrogen bonds involving the convergent N--H donor sites from nine guanidinium ions. The crystal structure of 3[(C2H5)4N+] · 20[C(NH 2)3+] · 11[C6H6(CH 3)3(COOH) (COO-)2] · [C6H6(CH3)3(COOH)2(COO -)]·17H2O (2.2.3) features a hydrogen-bonded aggregate with a centrosymmetric pseudo-octahedral arrangement of H2KTA- anions surrounding an inner core composed of eight guanidinium ions. The unusual twist-boat conformation of KTA3- is found in [(CH3)4N +] · 2[C(NH2)3+] · [C6H6(CH3)3(COO- )3] · 2H2O (2.2.6), which is stabilized by the co-existence of guanidinium and tetramethylammonium cations. / Systematic investigation on hydrogen-bonded supramolecular assembly using aromatic carboxylic acids bearing linear or bent skeletons with urea/guanidinium resulted in the formation of mainly R228 and R126 synthon motifs. In addition, isostructures were also constructed by varying the length of the linker between two carboxylate groups, as in naphthalene-2,6-dicarboxylate (2.3.2) and biphenyl dicarboxylate (2.3.3). / This thesis reports a systematic investigation on the generation of new inclusion compounds by the combined use of urea/thiourea, guanidinium ion and various organic anions as building blocks of hydrogen-bonded host lattices and selected quaternary ammonium ion as the enclosed guests. / Various acids bearing specific functional groups have been explored as structure building components, including boric acid, Kemp's triacid, heterocyclic (thio)urea derivatives, aryl and N-heteroaryl carboxylic acids and (dithio)squaric acid. All the co-crystals and inclusion compounds built of molecular components in the afore-mentioned categories have been characterized by single-crystal X-ray analysis. As a result, the complexes exhibit a rich variety of inclusion topologies, such as networks containing isolated cages, open channels, intersecting tunnels, double-layer systems, and sandwich-like as well as wave-like layer structures. / Han, Jie. / Adviser: Thomas C. W. Mak. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0337. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 204-218). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.

The increase in waste heat after consuming energy or burning fossil fuels is an issue environmentally and economically. Thermoelectric (TE) materials are developed to use in various applications because of their ability in converting waste heat into electricity. However, the applications are limited due to a low efficiency of materials, and research on thermoelectric materials is an on-going project for future use. Type-I clathrates are one of the TE materials which are studied in depth since the proposal of Slack’s PGEC (Phonon-Glass-Electron-Crystal) concept in 1995 due to their excellent thermoelectric properties. In this study, development and optimization of quaternary type-I clathrates will be the focus because double substitution often leads to better figure-of-merit, ZT, but it hasn’t really been studied. Higher ZT value is necessary because the energy conversion efficiency of TE materials is depending on the ZT value along with a larger temperature difference. Addition of lanthanoid elements as 2nd guest atoms to the main type-I clathrate structure, realized in Ba8Ga16Ge30, will be attempted to form quaternary compounds. The formation of the quaternary clathrates will be analyzed through powder X-ray diffraction, single crystal analysis and energy dispersive X-ray analysis. Also, as the performance of TE materials is examined through the figure of merit, ZT = TS²σ/κ, various techniques will be used to determine the Seebeck coefficient, the electrical conductivity and the thermal conductivity. The quaternary clathrates, Ba8-xLnxGa16Ge30 and Ba8-xLnxGa16+xGe30-x, where Ln = La, Ce and Eu were synthesized from the pure elements in stoichiometric ratios at 1000°C with slow cooling to room temperature. The products were then annealed at 600°C to acquire homogeneous samples for analyses. The various compositions of lanthanoid were intercalated into the structure of clathrates, which resulted in the quaternary clathrates with homogeneity. The crystal structure of quaternary clathrates with the space group of Pm-3n exhibited the same structure type as the ternary clathrates. The successfully formed products were refined with Rietveld refinements to understand their structures. The Eu containing clathrates crystallized with a lattice parameter a = 10.78251(6) Å, V = 1253.60(2) ų, for x = 0.3. The Ce containing clathrates also adopted the same space group with a lattice parameter a = 10.77331(6) Å, V = 1250.40(2) ų, for x = 0.3. The La containing clathrates formed with a lattice parameter a = 10.78494(6) Å, V = 1254.45(2) ų, for x = 0.3. Between 0.2 and 1.0 lanthanoid elements per formula unit were substituted with decreasing amount of barium where the actual amount of Ln in clathrates was lower than nominal amount. All these quaternary clathrates were found to be n-type semiconductors as determined through the Seebeck coefficient and electrical conductivity measurements.

This thesis examines the prospect of structure H (sH) hydrate to be exploited for methane storage. The methane content in the hydrate, hydrate kinetics and conversion rates are areas of particular importance. Experiments and theory are employed at the macroscopic and molecular levels to study the relevant phenomena. sH hydrate was successfully synthesized from ice particles with full conversion achieved within a day when thermal ramping above the ice melting point was applied. It was found that a polar guest (tert-butyl methyl ether / TBME) wets ice more extensively compared to two hydrophobic guests (neo-hexane / NH and methyl-cyclohexane / MCH). TBME also has much higher solubility in water. Consequently, the system with TBME was found to exhibit the highest initial hydrate formation rate from ice particles or in water in a well stirred vessel. However, the rate with the hydrophobic guests was the fastest when the temperature exceeded the ice point. Thus, the applied temperature ramping compensated the slow kinetics below the ice point for the hydrophobic guests and allowed faster overall conversion than the polar guest. Structure, cage occupancy, composition and methane content in the hydrate were also determined by employing different techniques and the results were found to be consistent. It was found that the methane content in structure H hydrate with TBME was the smallest (103-125 v/v) whereas that with NH was 130-139 (v/v) and that with MCH was 132-142 (v/v). The methane content in structure II hydrate by using propane (C₃H₈) and tetrahydrofuran (THF) as the large guest molecule were also estimated. Optimal methane content was found at approximately 100 (v/v) for both C₃H₈ and THF systems with the large guest concentrations at 1% for C₃H₈ (10°C) and 1% for THF (room temperature). The gas content is of course lower than that for structure I hydrate (170 v/v) but one should consider the fact that the hydrate formation conditions are much lower (less than 1 MPa). Finally, MD simulations revealed for the first time the formation of defects in the cavities for the TBME/methane/water (sH hydrate) system which may affect hydrate stability and kinetics.

The increase in waste heat after consuming energy or burning fossil fuels is an issue environmentally and economically. Thermoelectric (TE) materials are developed to use in various applications because of their ability in converting waste heat into electricity. However, the applications are limited due to a low efficiency of materials, and research on thermoelectric materials is an on-going project for future use. Type-I clathrates are one of the TE materials which are studied in depth since the proposal of Slack’s PGEC (Phonon-Glass-Electron-Crystal) concept in 1995 due to their excellent thermoelectric properties. In this study, development and optimization of quaternary type-I clathrates will be the focus because double substitution often leads to better figure-of-merit, ZT, but it hasn’t really been studied. Higher ZT value is necessary because the energy conversion efficiency of TE materials is depending on the ZT value along with a larger temperature difference. Addition of lanthanoid elements as 2nd guest atoms to the main type-I clathrate structure, realized in Ba8Ga16Ge30, will be attempted to form quaternary compounds. The formation of the quaternary clathrates will be analyzed through powder X-ray diffraction, single crystal analysis and energy dispersive X-ray analysis. Also, as the performance of TE materials is examined through the figure of merit, ZT = TS²σ/κ, various techniques will be used to determine the Seebeck coefficient, the electrical conductivity and the thermal conductivity. The quaternary clathrates, Ba8-xLnxGa16Ge30 and Ba8-xLnxGa16+xGe30-x, where Ln = La, Ce and Eu were synthesized from the pure elements in stoichiometric ratios at 1000°C with slow cooling to room temperature. The products were then annealed at 600°C to acquire homogeneous samples for analyses. The various compositions of lanthanoid were intercalated into the structure of clathrates, which resulted in the quaternary clathrates with homogeneity. The crystal structure of quaternary clathrates with the space group of Pm-3n exhibited the same structure type as the ternary clathrates. The successfully formed products were refined with Rietveld refinements to understand their structures. The Eu containing clathrates crystallized with a lattice parameter a = 10.78251(6) Å, V = 1253.60(2) ų, for x = 0.3. The Ce containing clathrates also adopted the same space group with a lattice parameter a = 10.77331(6) Å, V = 1250.40(2) ų, for x = 0.3. The La containing clathrates formed with a lattice parameter a = 10.78494(6) Å, V = 1254.45(2) ų, for x = 0.3. Between 0.2 and 1.0 lanthanoid elements per formula unit were substituted with decreasing amount of barium where the actual amount of Ln in clathrates was lower than nominal amount. All these quaternary clathrates were found to be n-type semiconductors as determined through the Seebeck coefficient and electrical conductivity measurements.