New cobalt (13, 16 19 and 22), manganese (14, 17, 20 and 23) and iron (15, 18, 21 and 24)phthalocyanine complexes were synthesized and characterized. The UV-Vis spectral properties of the complexes were typical of the nature of central metal and position of substituent on the Pc ligand. Their electrochemical behaviors were signatures of the central metals, with varying influences of the nature and position of substituents. Nanocomposite of complex 18 and single walled carbon nanotubes (SWCNTs) (SWCNT-18)was fabricated. Formation of this nano-composite was confirmed by infrared (IR)spectroscopy, X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Self-assembled monolayers (SAMs) of SWCNT-18, complexes 13-15, and 20 were electropolymerized on glassy carbon electrodes (GCE). Complex 14 was also electrodeposited on GCE. Surface properties of the SAMs were consistent with the molecular feature of the substituent and the nature of central metal in the adsorbed species, while those of the MnPc modified GCEs were dependent on point of substitution and number of substituent. The SAM-modified gold electrodes were used for the electrocatalytic oxidation of the carbamate insecticide, carbofuran. Amplification of the current signal of the insecticide, at more energetically feasible oxidation potentials, on the SAM-modified gold electrodes, relative to bare gold electrode,justified electrocatalysis. There was enhanced sensitivity (attributed to the presence of SWCNT) of the SWCNT-18-SAM-modified gold electrode towards carbofuran, relative to the signals observed on the other SAMs. Current response of the insecticide,bendiocarb, was also intensified, at more favorable oxidation potentials, on the MnPc (14 and 17) modified GCEs, relative to the response on bare GCE, substantiating electrocatalysis. Also, catalysis of the oxidation of the herbicide, bentazon, was observed on polymeric film of complex 20. The current response of the herbicide on this film was better than that observed on bare GCE. Electrocatalysis of the analytes, on the respective modified electrodes, occurred via closely related mechanisms.

The synthesis of symmetrically and unsymmetrically substituted zinc phthalocyanines (ZnPc) derivatives is done according to reported procedures. The unsymmetrical ZnPc derivatives are synthesized by ring expansion of sub-phthalocyanine complexes. Ring substitution is effected with tert-butyl phenol, naphthol, and hydroxybenzoic acid. Comparison of the redox potentials for the complexes substituted with varying numbers of tert-butyl phenol: 1, 2, 3, 6 and 8 show that the complex with the highest number of substituents are more difficult to oxidize and easier to reduce. Water soluble sulphonated ZnPc (ZnPcSn) was prepared. The possibility of using axial ligation to increase the solubility and the photochemical activity of sulphotnated ZnPc in aqueous solutions was investigated. Pyridine, aminopyridyl and bipyridyl were used as axial ligands. When bipyridyl was used as the axial ligand, solubility of the ZnPcSn increased, shown by the increase in the Q-band of the monomer species in solution and the singlet oxygen quantum yields was relatively higher than that of the unligated ZnPcSn. The singlet oxygen quantum yields by the various complexes in DMF using diphenylisobenzofuran as a chemical quencher for organic solvent were determined. Singlet oxygen quantum yields for the unsymmetrically ring substituted complexes range from 0.22 to 0.68. Photobleaching quantum yields are in the order of 10-5, which means that the complexes are relatively photostable.

Substituted zinc and magnesium phthalocyanine and porphyrazine derivatives were synthesized according to the reported procedures. The magnesium and zinc phthalocyanine and porphyrazine derivatives were synthesized by ring enlargement of subphthalocyanine and statistical condensation of the two phthalonitrile derivatives. Characterization of the complexes involved the use of infrared spectroscopy, nuclear magnetic resonance spectroscopy, ultraviolet and visible spectroscopy, and Maldi-TOF spectroscopy (for selected compounds) and elemental analysis. Photochemical and photophysical properties of the complexes in non-aqueous solution was then investigated. Photobleaching quantum yields are in order of 10⁻⁵ indicating their relative photostability. Complexes containing more electron-donating substituents were more easily oxidized. For complexes 66 and 69 (as these complexes have the same number of substituents but differ in the metal center) photobleaching quantum yield for the ZincPc complex 69 was slightly less than that of the MgPc complex 66. Singlet oxygen quantum yields of the various complexes in DMSO using diphenylisobenzofuran (DPBF) as a quencher in organic solvents were determined. Singlet oxygen quantum yields of the complexes range from 0.23 to 0.67. High values of Φ[subscript]Δ ZnPc complexes was observed compared to the corresponding MgPc, complexes. This was evidenced by complexes 66 and 69 with Φ[subscript]Δ values of Φ[subscript]Δ = 0.26 and 0.40, respectively. Varying number of phenoxy substituents, complex 71 gave significantly large value of Φ[subscript]Δ compared to 70 (that is, the presence of more electron-donating substituted group, gave higher singlet oxygen quantum yields (0 .67 and 0.25 for 71 and 70 repectively). The triplet quantum yields and triplet lifetimes were determined by laser flash photolysis for selected compounds. The triplet quantum yields increase as the number of substituents increases e.g 68 > 67 > 66. Comparing porphyrazine complexes (63, 64 and 65), 63 with benzene attached to the ring, has higher triplet state lifetime (420 μs) compared to 64 and 65 containing long alkyl chain and tertbutyl substituents, 350 and 360 μs,respectively). The observed Φ[subscript]f values for 68 and 63 were quiet suprising, since low values are observed compared to the rest of the complexes (e.g 0.03 and 0.02 respectively). Although these values seem so low, they are sufficient for fluorescence imaging applications. The Φ[subscript]f values for the complexes under study are within the range reported for complexes currently used for PDT. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in

A detailed photophysicochemical study of some non-transition metal (AI, Zn, Si, Ge, and Sn) metallophthalocyanine (MPc) derivatives is presented. The effects of substituents, central metal ions and solvents on the photophysical and photochemical properties are investigated and rationalized accordingly. The presence of peripheral substituents on the macrocycle enhances the yield of the triplet state. Near infra-red absorptions of the solvents reveal that solvents which absorb around 1100 nm and around 1270 nm, quench the triplet state of the MPc derivative and singlet oxygen, respectively. Although water has a high singlet oxygen quenching effect, the singlet oxygen quantum yield (Φ∆) value for sulphonated zinc phthalocyanine in water is still reasonably high at 0.48, which may provide an explanation for the efficient photosensitization by this molecule in photodynamic studies. The lowering of Φ∆ following protonation of the MPc macrocycle is attributed to the lowering of triplet energy to the level where energy transfer to ground state oxygen is no longer favourable. MPc inclusion complexes with cyclodextrins showed larger Φ∆ values when compared to the complexes before inclusion. Job's plots show that 2:1 and 4:1 (CD:MPc) complexes may be formed. Fluorescence quenching by electron donors and acceptors were analysed by StemVolmer relationship and the results used in determining fluorescence lifetimes of the complexes. Qualitative and quantitative interpretations of the interaction of sulphonated MPcs with bovine serum albumin (BSA) are provided in this thesis. 1:1 adducts were formed with BSA, but the binding feasibilities varied markedly. Spectral, photophysical and photochemical properties of the complexes are altered in the presence of BSA.

The synthesis, photophysicochemcial properties, in vitro dark toxicity and photodynamic therapy (PDT) activities of different derivatives of zinc phthalocyanine (ZnPc) conjugates with biomolecules (folic acid, bovine serum albumin (BSA), ascorbic acid, uridine or spermine) and single-walled carbon nanotubes (SWCNTs) are presented in this work. The fluorescence quantum yields (ΦF) (Subscript F) of the ZnPc derivatives or ZnPc-biomolecule conjugates remained relatively the same as compared to the precursor Pcs. Slight increases were observed in the ΦF (Subscript F) values of conjugates containing substituents such as pyrene, folic acid or BSA with intrinsic fluorescence properties. The triplet quantum yield (ΦT ) (Subscript T) values for some ZnPc conjugates increases compared to the precursor ZnPcs due to extended π conjugation (for the conjugate with pyrene) and the presence of phenyl ring that support spin-orbit charge transfer intersystem crossing to triplet state. While some conjugates showed decreases in the ΦT (Subscript T) values compared to precursor ZnPcs due to the presence of substituents that could quench photo-excited state properties. The singlet oxygen quantum yield (ΦΔ ) values follow the trends of the triplet quantum yield values. The conjugates containing BSA also show increases in the ΦΔ values without corresponding increases in ΦT (Subscript T) values due to the ability of BSA to generate free radicals including singlet oxygen. The presence of SWCNTs decreases the photophysicochemcial properties of some ZnPc-SWCNT conjugates compared to the precursor ZnPcs due to photo-induced electron transfer from an excited Pc complex (electron donor) to SWCNTs (electron acceptor). However, increases were observed in some ZnPc-SWCNT conjugates as a result of fast charge recombination process due to highly short-lived radical ion pair produced. These phenomena affected the ΦF (Suscript F) values, ΦT (Suscript T) values, and the ΦΔ values. Increases or decreases in ΦT (Suscript T) values resulted in corresponding increases or decreases in ΦΔ values

Syntheses, spectral, photophysical and photochemical studies of some neutral, anionic and cationic metallophthalocyanine derivatives are presented. The effects of central metal ions, solvents, aggregation, surfactant, nanoparticles and bovine serum albumin on the photophysical and photochemical behaviour are investigated. Mercaptocarboxylic acid stabilized CdTe quantum dots (QDs) were used as energy donors to anionic water-soluble MPcs through Förster resonance energy transfer (FRET). Energy transfer (ET) from the QDs to the MPcs occurred upon photoexcitation of the QDs. An enhancement in efficiency of ET with the nature of the cappings on the QDs was observed with few occurrences of a non-Förster type ET. QDs were found to improve the photophysicochemical behaviour of the MPcs, with the possibility of indirect production of singlet oxygen (Φ[subscript Δ]) via FRET mechanism. Interaction of the QDs with cationic water-souble MPcs produced ion-pair complexes resulting in aggregates due to strong electronic coupling. The stoichiometry of the reaction and association constants are evaluated by the continuous variation method. Improved photophysicochemical behaviour with no spectral alterations was observed in MPcs in the presence of magnetic fluid. Complexes showed high triplet quantum yields with corresponding long lifetimes and high photostability. Elucidation of the results of the interaction of bovine serum albumin (BSA) with MPcs or QDs is presented. Increased efficiency of Φ[subscript Δ] generation of MPcs in the presence of BSA coupled with large binding constants, suggesting strong interaction of the MPcs with BSA was observed. Enhanced emission intensity of QDs when linked to or in a mixture with BSA due to radiationless recombination at the surface vacancies was also observed. The study revealed positive deviation from Stern-Volmer relationship suggesting the occurrence of static and dynamic mechanisms of quenching together. Fluorescence quenching of the MPcs by benzoquinone, analysed by Stern-Volmer relationship is also presented; the results were employed in determining fluorescence lifetimes of the complexes. Photoelectrochemical characteristics of MPc-sensitized electrodeposited ZnO thin films were studied; ZnOCPc / ZnO films have been improved to an incident photon-to-currentconversion (IPCE) value of 31.1 % with an absorbed photon-to-current conversion (APCE) of 59.6 %. The best obtained so far with phthalocyanine-type sensitizers on nanocrystalline ZnO films. Fluorescent-magnetic nanocomposite with excellent photophysical properties which can be exploited for combined photodynamic and hyperthermia therapies is also presented.

A number of metallophthalocyanines (MPcs) and metal-free phthalocyanines (H₂Pcs) have been synthesized and characterized using various characterization tools such as ¹H-NMR, TOF mass spectrometry, FT-IR, UV-visible spectrophotometry and CHNS elemental analysis. Some of the MPcs were covalently linked to nanomaterials such as silica nanoparticles (SiNPs), single-walled carbon nanotubes (SWCNTs), magnetite nanoparticles (MNPs) and quantum dots (QDs), or embedded in polymer thin-films using poly(methyl methacrylate) (PMMA) and poly(acrylic acid) (PAA) as the polymer sources. The phthalocyanine-nanomaterial composites (Pc-NMCs) were characterized with FT-IR, UV-visible spectrophotometry, transmission electron microscopy (TEM), thermogravimetry analysis and X-ray diffractometry. The nonlinear optical (NLO) properties (using the open-aperture Z-scan technique) of the MPcs and the Pc-NMCs were investigated. In general, most of the investigated MPcs showed good optical limiting behaviors, except for a few, like the non-peripherally-substituted 2-pyridyloxy phthalocyanines, which showed inhibited NLO response as a result of the ring-strain effects. The absence of a metal center was found to greatly reduce the inherent high nonlinearities expected of some of the phthalocyanine complexes. The octaphenoxy derivatives (61a – 61e) were found to exhibit reverse saturable absorption (RSA) that depends on the singlet-singlet transitions, hence making them less reliable optical limiters. The optical limiting properties of the MPcs were improved in the presence of nanomaterials such as the QDs, MNPs and SWCNTs, with MPc-QDs showing the best optical limiting behavior of the three. SiNPs have no significant effect on the optical limiting behavior of the MPcs. The optical limiting properties of the MPcs were greatly enhanced in the presence of PMMA or PAA polymers. The PAA polymer showed better optical limiting behavior compared to PMMA

Various axially substituted Silicon octaphenoxyphthalocyanines were synthesised as potential photosensitisers in the photodynamic therapy of cancer. Conventional reflux reactions were used for synthesis as well as new microwave irradiation reactions, wherein the reaction times were decreased tenfold with a marginal increase in reaction yield and product purity. An interesting series of oligomeric (dimer to a nonamer) silicon octaphenoxyphthalocyanines were also successfully synthesised in a reaction similar to polymerisation reactions. These compounds were found to undergo an axial ligand transformation upon irradiation with red light (> 600 nm) in dimethylsulphoxide solution. All the ligands were transformed into the dihydroxy silicon octaphenoxyphthalocyanine with varying degrees of phototransformation quantum yields ranging in order from 10⁻³ to 10⁻⁵ depending on the axial ligand involved. During and after axial ligand transformations a photodegredation of the dihydroxy silicon octaphenoxy phthalocyanine was observed upon continued irradiation. The oligomers were found to undergo the same axial ligand transformation process with a phototransformation quantum yield of 10⁻⁵ The singlet oxygen quantum yields of the unaggregated monomeric silicon octaphenoxy phthalocyanines were all found to be approximately 0.2 with the exception of a compound with two (trihexyl)siloxy axial substituents that had a singlet oxygen quantum yield of approximately 0.4 in dimethylsulphoxide solutions. The oligomers showed a surprising trend of an increase in singlet oxygen quantum yield with an increase in phthalocyanine ring number up to the pentamer and then a dramatic decrease to the nonamer. The triplet quantum yield and triplet lifetime were determined by laser flash photolysis for selected compounds and no correlation was observed with any of these properties and the singlet oxygen quantum yields. These selected compounds all fluoresce and a very good correlation was found between the fluorescence lifetimes determined experimentally by laser photolysis and the Strickler-Berg equation for the non-aggregated compounds. Electrochemical measurements also indicate the importance of the axial ligands upon the behaviour of the phthalocyanines as cyclic voltammetric behaviour was determined by the nature of the axial ligand.

This work presents the nonlinear properties of six Sn(IV) Phthalocyanines. Three of the phthalocyanines are linked by an alkylthiol substituent and the rest are linked with a phenoxy substituent. For all six compounds non-linear optic analysis was carried out in four solvents: chloroform, toluene, dichloromethane, and tetrahydrofuran, and their differences were recorded. Calculation of the linear, singlet excited, triplet excited and two photon absorption cross-sections were also carried out and the results compared. To form a comparison the first order hyperpolarizabilities, DFT calculations were also performed and the results compared to see if the behaviour between the two properties can be predicted using DFT.

No description available.