This thesis presents the synthesis of neutral and cationic metallophthalocyanines and their gold nanoparticles conjugates. The spectroscopic characterization of these compounds is presented herein. The studies presented in this work shows that the conjugation of gold nanoparticles influenced both photophysical and photochemical properties. Gold nanoparticles were found to enhance the singlet oxygen quantum yield while lowering the fluorescence quantum yields. This work also looks at the effect of anisotropic gold nanoparticles such as nanorods and bipyramids on the photophysical behaviour of the metallophthalocyanines. The effect of the size of the gold nanorods was investigated herein. The results show that photophysical and photochemical properties can be influenced by both size and shape of the nanoparticles. Physical characterization about the loading of nanoparticles was also looked into. Parameters such as the surface area, the number of surface atoms, the number of atoms as well as the number of nanoparticles loaded on the surface of the phthalocyanines were studied. The self-assembled monolayers formed by phthalocyanines on gold surfaces were studied using the X-ray photoelectron spectroscopy (XPS). The gold nanoparticles synthesized herein include both organic and water soluble, different capping agents (citrate, tetraammonium bromide (TAOBr) and cetrimethylammonium bromide (CTAB). The concentration of the gold nanoparticles was measured on the inductively coupled plasma (ICP) and their size and shape were obtained from the transmission electron microscopy (TEM) images. A cationic aluminium phthalocyanine and its conjugates were used for photoinactivation of bacteria and fungi. The results show significant reduction and higher activity in the presence of gold nanoparticles, especially nanorods. A small chapter in this work presents an attempted work on the binding of metallothionein protein with protophorphyrin (IX). The pH and concentration dependent binding studies were investigated

The photoaquation mechanisms for a series of Cr(III) am(m)ine complexes have been investigated using laser flash photolysis with conductivity detection. The observation of transient increases in solution conductivity at pH > 4 and a conductivity decay lifetime longer than the doublet emission decay lifetime at pH < 3, have confirmed an intermediate in the photoaquation of cis-Cr(cyclam)(NH₃)₂³⁺. Transient increases in solution conductivity characteristic of an intermediate species were also observed for Cr(en)₃³⁺, Cr(tn)₃³⁺ and Cr(sen)³⁺ at pH > 4. The conductivity changes occurring in solution have been modelled for possible photoaquation mechanisms for the am(m)ine complexes, based on numerical integration of the rate expressions for all relevant mechanistic species. The comparison of these results with experimental data indicates that the intermediates observed for Cr(en)₃³⁺, Cr(tn)₃³⁺ and Cr(sen)³⁺ are the initially formed photoproducts, Cr(NN)₂(N-N)(OH₂)³⁺, where NN = a bidentate ligand or a sen arm. These species can undergo two processes, protonation of the dangling amine arm, or deprotonation of the aquo group. At low pH the first process dominates and conductivity decays due to proton uptake are observed. As the pH of the solution increases, the second process becomes competitive, and transient increases in solution conductivity are observed when this becomes the faster process. The modelled results for cis-Cr(cyclam)(NH₃)₂³⁺ indicate that the photoaquation occurs via two modes; (i) direct loss of ammonia, and (ii) loss and recoordination of a cyclam to displace ammonia, with both modes generating the observed photoproduct, cis-Cr(cyclam)(NH₃)(OH₂)³⁺. The modelling indicates that 0.67 of the overall photochemistry occurs via the cyclam loss mode. The intermediate has been identified as the initial product of the cyclam loss mode. Cr(cyc-N)(NH₃)₂(OH₂)³⁺. The rate of reaction observed via this mode is limited by the recoordination of the cyclam amine. As this is slower than the rate of doublet decay, the conductivity lifetimes observed at pH < 3 are longer than the doublet lifetime. The slow rate of recoordination also delays the release and subsequent protonation of ammonia, allowing for competitive deprotonation of the aquo group at pH > 4, and generating the observed transient increases in solution conductivity. The relevance of these results to Cr(III) chemistry in general, including possible ²E state reaction mechanisms is discussed. The photoaquation of Cr(CN)₆³⁻ was investigated using laser flash photolysis with conductivity detection. Theory predicts that the signal magnitudes observed for this complex should be constant throughout the pH range 2.7 - 5.3. Experimental results showed that the observed signals dropped from a maximum of 120 mV at pH 2.75 to 45 mV at pH 5.25. Possible explanations for this pH dependence are presented. The stereochemistry of the thermal and photoaquation products of rac- & Λ-Cr(sen)³⁺ has been investigated using capillary electrophoresis. Two products were found in the photoaquation reactions, trans-Cr(sen-NH)(OH₂)⁴⁺ and a product resulting from loss of a secondary amine. The thermal reaction produced trans-Cr(sen-NH)(OH₂)⁴⁺ as the major product with virtually no cis-Cr(sen-NH)(OH₂)⁴⁺ enantiomers being observed. Efficient racemization of Λ-Cr(sen)³⁺ to Δ-Cr(sen)³⁺was also observed in the thermal reaction, consistent with racemization occurring via bond rupture and recoordination. The photoaquation results are discussed in terms of VC theory and a reinterpretation of conflicting literature results for the thermal and photochemical aquation of Cr(sen)³⁺ is presented. / Graduate

The cross section for the photodisintegration of a three body nucleus, helium-3, has been accurately measured for the first time. The He³( ɣ,p)D reaction cross section has been measured at gamma ray energies of 6.14, 6.97 and 7.08 Mev and found to be 0.104 ± .007, 0.298 ± .050 and 0.308±.024 milli-barns respectively. The photodisintegration cross section agrees with that calculated from the D(p,ɣ)He³ reaction using the principle of detailed balance to within the experimental errors. This is an accurate verification of this principle as applied to a direct nuclear-photon interaction. The photodisintegration reaction was observed in a cylindrical gridded ionization chamber using a helium-3, methane, and argon gas mixture. The F¹⁹(p, αɣ)016 reactions at proton bombarding energies of 873.5 kev and 935 kev were used as the source of gamma rays of well defined energy. The energy resolution of the chamber was adequately good to give a reasonable separation of the 642 kev photodisintegration reaction product peak from the electron background and the 765 kev peak from the He³(n,p)T reaction. It was necessary to reduce the tritium contamination in the helium-3 gas in order to reduce the background arising from the beta decay of the tritium; purification to less than 1 part tritium in 10¹⁰ parts helium was achieved. Proposed measurements of the photodisintegration cross section at higher gamma ray energies using ionization chambers and other types of detectors are discussed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In order to elucidate the mechanism of hydrogen sulphide oxidation, the photo-oxidation and thermal oxidation of hydrogen sulphide were studied, using gas chromatography for the analysis of final products. Photo-oxidation was studied at 130° and 150°C. Products found were sulphur dioxide, hydrogen, water and sulphur. Production of sulphur dioxide was found to be inhibited by an increase in surface area. Whether in photo- or thermal oxidation, the yield of sulphur dioxide increased drastically with slight increases in (O₂)/H₂S) ratio. This was also observed in the yield of hydrogen in photo-oxidation. Thermal oxidation was studied at 160°, 170°, 190°, 210°, 225°, 240°, and 260°C. Products were sulphur dioxide, water, and sulphur. No hydrogen was found. An expression for the production of sulphur dioxide was obtained: [formula omitted] = k (H₂S)⁻¹→⁺¹ (O₂)³ The overall activation energy was found to be 21.2±2k.cal./mole. Comparison with previously reported works was made and a mechanism proposed. / Science, Faculty of / Chemistry, Department of / Graduate

Energy transfer between Reineckate ion (donor) and hexacyanochromate(III) ion (acceptor) has been studied through quenching of donor phosphorescence (lifetime and intensity) and sensitization of acceptor phosphorescence. Results from all measurements fit the expected Stern-Volmer relationship with a quenching constant kQH = 7.2 x 10⁵ M⁻¹ sec⁻¹ at -65°C. The pre-exponential factor and activation energy of kQH are 6.6 x 10¹º M⁻¹ sec⁻¹ and 4.8 Kcal/mol respectively. The constant, kQH’ is attributed entirely to an energy transfer rather than a quenching process. The electronic states directly involved are the ²Eg (and/or² T₁g) states of both donor and acceptor. Energy transfer is a diffusion-controlled (collisional) process. Hexacyanochromate(III) ion is itself quenched in the presence of Reineckate ion. The quenching constant, k'QH, which may be attributed to back energy transfer from acceptor to donor, has a pre-exponential factor of 2 x 10¹² M⁻¹ sec⁻¹ and an activation energy of 7.6 Kcal/mol. In the same system, quenching of photoaquation has also been studied at -65°C. The photoaquation quantum yield of Reineckate ion is 1.02 x 10⁻². It is reduced in the presence of hexacyanochromate(III) ion, but not as much as the phosphorescence of Reineckate ion is reduced. The limiting unquenchable part, ϕ∞chem, occurs via the ⁴T₂g state, while the quenchable part must occur through the ²Eg state as an intermediate. The actual path for the quenchable part proposed is back intersystem crossing from the ²Eg to the ⁴T₂g state, which then undergoes aquation. The primary processes of ²Eg state molecules have been investigated through the temperature dependence of phosphorescence lifetimes of some Cr(III) complexes. All the available evidence supports the idea of the thermally activated back intersystem crossing. According to this mechanism, the origins of the ⁴T₂g states of Cr (III)complexes reached by crossing are far lower in energy than has been expected. Assuming the occurrence of back intersystem crossing, the application of energy transfer to the determination of intersystem crossing quantum yield, ϕisc’ has been demonstrated. The values of ϕisc for Reineckate and hexacyanochromate (III) ions are estimated to be 0.52 and 0.35, respectively. The variation of ϕisc with temperature for these Cr(III) complexes has also been measured, which suggests that in general, internal conversion has a strong temperature dependence. From the rise of phosphorescence with time after pulse excitation, a new parameter, Tx, has been obtained which represents population of the phosphorescing state and is believed to be the lifetime of the ⁴T₂g (or less likely ²T₁g) state. Efforts have been made to confirm and identify this parameter. Studies of ϒx have been carried out as a function of temperature. Mechanisms based on different tentative assignments of ϒx are proposed and their implications examined. All primary processes, except the intrinsic radiative transitions, seem to consist of at least two components, which take different pathways and are different functions of temperature. / Science, Faculty of / Chemistry, Department of / Graduate

The pyrolysis of azoethane has been studied in a static system in the temperature range 245 to 308°C., and at initial pressures between 15 and 110 mm. using gas chromatographic analysis. In the initial stages of the reaction, products identified are methane, ethane, ethylene, propane, propylene, n-butane, nitrogen and di- and tri- ethyl amines. At large extents of the reaction radical-olefin reactions occur extensively and produce a complex distribution of products. Compounds containing carbon, hydrogen and nitrogen are also formed at higher percentage decompositions. The orders of formation of major products with respect to azoethane, as well as activation energies, have been determined. The activation energy for the initiation reaction C₂H₅N₂C₂H₅ → 2 Ċ₂H₅ + N₂ has been found to be 47.2 ± 1.0 kcal per mole. The effects of additives such as cis-butene-2, butene-1 and carbon dioxide on the initial rates of formation of various products have been investigated. All the additives have a common effect of lowering the initial rate of formation of ethane. Increase in surface: volume ratio has the effect of lowering the time rate of pressure change by 10 to 20% and this has been attributed to the increased surface recombination of radicals. The rate of formation of ethane is also decreased in the packed reaction vessel. This study has pointed out that there is a short chain in the thermal decomposition of azoethane due to the formation and subsequent decomposition of CH₃ĊH-N=N-CH₂CH₃ radical. A mechanism has been proposed for the pyrolysis of azoethane which accounts qualitatively for the nature and distribution of products. The flash photolysis of azoethane has also been investigated at room temperature in pyrex and quartz reaction vessels. Thermally equilibrated radicals are produced in the pyrex cell with outer pyrex jacket. Addition of large amounts of carbon dioxide in the flash photolysis of azoethane decreases the product yields indicating the collisional deactivation of excited azoethane molecules. The ratio of ethyl radicals disproportionation to combination has been found to be 0.12 ± 0.02. Reactions have been postulated to account for the products of flash photolysis of azoethane. / Science, Faculty of / Chemistry, Department of / Graduate

In the first part of this work the thermal reaction [Formula omitted] was studied thermodynamically and kinetically in the gas phase and at the temperature range 150 to 210°C. The equilibrium composition was found to be very unfavourable to 3-butenal which constitutes 0.35% of the mixture at 150°C and 1.04% at 210°C. The enthalpy of the reaction was estimated to be 7.20 ± 0.09 kcal/ mole. In the kinetic study both the forward and reverse reactions were found to be heterogeneous and of the first order with respect to surface area and pressure of reactant. The rate constants obeyed the relations [Equation omitted] k₁ was determined in a vessel with surface to volume ratio equal to 1.2 and k₋₁ in a vessel with ratio equal to 4.1. The significance of the experimental Arrhenius parameters was discussed in terms of the theory of absolute rates as applied to surface reactions and of a mechanism based on a fast adsorption-desorption of the Langmuir type. In the second part of the work the photochemical isomerization of crotonaldehyde to 3-butenal was studied in the gas phase and at the temperature range 25 to 140°C. Exciting radiation of the wavelengths 3130, 3340 and 3660 Å was used. It was found that the quantum yield of the isomerization obeys the Stern-Volmer equation 1/ϕ = a + bP ein/mole at the temperature and wavelength range studied. The pressure, P, of crotonaldehyde was varied from 0.4 to 34 mm Hg. The value of parameter a varies from 11 to 37 ein/mole with the low values observed at 3130 Å and the high values at 3660 Å. The parameter b varies from 0.19 to 7.5 ein.mole⁻¹ (mm Hg)⁻¹ with the low values also observed at the shorter wavelength. At constant wavelength b decreases with increasing temperature. A mechanism was discussed according to which the excited singlet '(n,π* ) is the reacting species and it was shown that a "strong collision" deactivation and a classical energy distribution function predict qualitatively the dependence of b on temperature and wavelength. An attempt to predict this dependence in a quantitative manner failed. A refinement to the "strong collision" mechanism using the same energy distribution function could not be tested numerically because of computational difficulties. An alternative mechanism was discussed involving a cis-trans equilibrium of crotonaldehyde in the ground state and it was shown that the parameters a and b may be interpreted in more than one way. In the third part of the work the photolysis and photochemical oxidation of 3-butenal were studied in the gas phase and the temperature range 25 to 140°C. In the photolysis exciting radiation of 3130 and 3340 Å was used. The products were carbon monoxide, propylene and biallyl. They were found to obey the relation CO ≤ propylene + 2.biallyl The overall quantum yields taken as equal to ϕ (propylene) + 2 ϕ (biallyl) obeys the Stern-Volmer equation (1). The Value of the parameter a varies from 0.994 to 1.226 ein/mole and that of b from 1.15 x 10⁻² to 3.75 x 10⁻² ein. mole⁻¹ (mm Hg)⁻¹ . The lowest values for both parameters are observed at 3130 Å and 140°C and the highest at 3340 Å and 25°C. The significance of parameter a was discussed and it was shown that its dependence on temperature and wavelength can be predicted within the limits of the experimental error by using the classical energy distribution function. In the photochemical oxidation radiation of 3130 Å was used. The major products with the quantum yields at 25°C shown in paranetheses were: carbon monoxide (3.0-3.4), allyl alcohol (1.1-2.4), acrolein (1.2-1.9), carbon dioxide (0.4-1.0), propylene (0.4-0.5), peroxide (0.20-0.27) and ethylene (0.22-0.27). Variation of the experimental conditions at constant temperature had little effect on the quantum yields. Increase of temperature to 140°C resulted in decrease of the yield of allyl alcohol and acrolein and increase of the yield of all the other products. A mechanism was discussed which explains the results in a qualitative way. / Science, Faculty of / Chemistry, Department of / Graduate

The thermal and photolytic decomposition of cis and trans_-3,5-dimethyl-3-acetyl-Δ¹-pyrazoline have been found to give six products. They have been separated and identified as 2,3,5-trimethyl-Δ²-dihydrofuran, cis and trans-1,2-dimethyl-1- acetyleyclopropane, cis and trans-3-methyl-3-hexen-2-one and 3-methyl-4-hexen-2-one. The formation of cyclopropanes by photolysis showed some degree of stereospecifIcity. Both pyrolysis and photolysis yielded olefins with high degree of stereospecificity. 2,3,5-TrImethyl-Δ²-dihydrofuran was a major product from the decomposition of cis-3,5-dimethyl-3-acetyl-Δ¹ -pyrazoline only. Pyrolysis gave a higher ratio of olefins to cyclopropanes than photolysis. These decomposition reactions gave results analogous to those of cis and trans-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazoline. The product compositions from both the pyrolysis and photolysis of cis and trans_-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazoline have been found to show a small and regular influence of the solvent and this has been related to the dielectric constant of the solvent. Pyrolysis and photolysis gave an olefin to cyclopropane ratio of 57:43 and 21:79, respectively, in formamide, and 7:93 and 5:95, respectively, in cyclohexane. A small kinetic solvent effect has been observed for the pyrolysis of 3,5-dimethyl-3-carboraethoxy-Δ¹-pyrazoline. The rate of pyrolysis as followed by the rate of nitrogen evolution has been found to decrease for the following series of solvents: dl-n-butyl ether, tetralin, nitrobenzene and form-amide. These rates were all within a factor of three. The absence of rate enhancement in a solvent of high dielectric constant has been used as an argument against an ionic Intermediate in these reactions. Liquid phase photolysis of trans-3,5-dimethyl-3-carbo- methoxy-Δ¹-pyrazolIne at various temperatures ranging from -55ᵒ to 58ᵒ did not show appreciable change in the product compositions attributable to the influence of temperature. The solvent temperature therefore does not affect the amount of quenching of any "hot" intermediate. Photolysis and pyrolysis of cis and trans-3,5-dimethy1-3-carbomethoxy-Δ¹ -pyrazoline under identical conditions did not give the same product composition. This suggested the two reactions do not have a common Intermediate. No isomerization between the cis and trans-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazolines has been observed as shown by the partial pyrolysis and photolysis of the trans-pyrazoline. These results are discussed In view of current mechanistlc proposals for the pyrolysis and photolysis of Δ¹-pyrazolines. / Science, Faculty of / Chemistry, Department of / Graduate

In Part I of this work octahydro-4a, 8a-epoxy-l(2H)-naphthalenone, hexahydro-3a,6a-epoxy-l(2H)-pentalenone, and octahydro-3a,8a-epoxy-4(lH)-azulenone were photolyzed. The major course of these reactions was one of polymerization. Small amounts of monomeric products could however be obtained with difficulty and were tentatively assigned the structures which arise mechanistically via the same path as in the rearrangement of ordinary aliphatic α,β-epoxy ketones i.e, 1,3-diketone formation. In order to prove the structure of the photoproduct of the naphthalenone epoxide the synthesis of 2-cyclopentylidene-cyclopentanone oxide was attempted. In Part II of this thesis the nature of the excited state in the photolysis of cis, cis-cyclodeca-3, 8-diene-l, 6-dione was investigated by quenching and sensitization experiments. These suggested that the reactive excited state involved was a highly reactive triplet state. Furthermore, the thermal reaction of cis, trans-cyclodeca-3, 8-diene-1, 6-dione was investigated and found to give rise to three new products in low yields whose structures are still under investigation. They probably arose from an ene-reaction. Thermolysis of cis, cis-cyclodeca-3, 8-diene-1, 6-dione afforded 3a, 5, 8, 8a-tetrahydro-8a-hydroxy-4(1H)-azulenone. A low temperature photolysis of cis, trans-cyclodeca-3, 8-diene-l, 6-dione was carried out at 77°K in order to trap the potential intermediate trans, trans-cyclodeca-3, 8-diene-l, 6-dione. However, besides a minor amount of cis, cis-isomer, the low temperature photolysis afforded the same product as that obtained by photolysis at ambient temperature. Finally the centrosymmetric anti-configuration of the tricyclic photo-product from cis, cis-cyclodeca-3, 8-diene-l, 6-dione was further supported by a dipole measurement and by infrared and Raman spectroscopy. / Science, Faculty of / Chemistry, Department of / Graduate

The photochemistry of a variety of tetrahydro-1,4-naphthoquinones (structure 1) has been investigated. These were synthesized by Diels-Alder reaction of corresponding p-quinones and acyclic-1,3-dienes [diagram omitted]. Three substituent-dependent types of reactions were observed: (1) for adducts possessing hydrogen substituents at C₄a and C₈a (bridgehead position), the prevalent process was one of abstraction of a β-hydrogen atom from C₅(or equivalently, C₈) by excited carbonyl oxygen. In general, three product types were then observed, derived from carbon-carbon bond formation (proceeded in two instances by conformational rotation about the C₄a - C₈a bond) in the bisallylic radical so produced. Placing a methyl or phenyl substituent at C₂ renders the β-hydrogens non-equivalent, and abstraction occurs in accord with expectations based on the formation of the more stable biradical intermediate. In adducts possessing bridgehead substituents, rotation about the C₄a - C₈a bond in the biradical is suppressed and only a single product type (enone alcohol) is formed, which possesses the same relative conformation as the biradical and starting adduct. In the case where the bridgehead substituents are carboxymethyl, however, secondary photolysis in benzene solution occurs, giving rise to a product where the bridgehead substituents are nearly eclipsed. (2) For the adduct possessing exo-methyl substituents at positions 5 and 8 as well as methyls at the bridgehead positions and at and C₂ and C₃, hydrogen abstraction was partially suppressed in favor of a process tentatively concluded to involve Ύ~hydrogen abstraction by excited enone carbon, giving rise to a product, the formation of which again requires little conformational change in the biradical. (3) For adducts possessing endo-methyl substituents at C₅ and C₈ as well as bridgehead substituents, a novel oxetane product was observed, formally the result of a cycloaddition reaction involving the remote double bond and one of the carbonyl groups. The oxetane derived from the duroquinone adduct was found to be photolabile, giving back starting material and, eventually, a quantitative conversion to a novel cage diketone. The reactivity differences for these systems, as well as for those previously studied in our laboratory, are interpreted as being due to the effects of substituents on the energy barrier to conformational isomerization in the biradical intermediates. Finally, the potential utility of these photochemical reactions for the synthesis of unusual ring systems is noted. / Science, Faculty of / Chemistry, Department of / Graduate