This thesis assesses the possible photochemical transformations of nitrogen fixed in organic compounds. The aim of this study was to monitor the kinetics and seasonal trends in photochemical degradation of dissolved organic matter and nitrogen in the first order stream.

The combination of chemotherapy and photodynamic therapy was investigated by synthesis and characterization of octacarboxy phthalocyanine covalent conjugates with platinum complexes. This work presents the synthesis, characterization and photophysicochemical properties of aluminium (diaquaplatinum) octacarboxyphthalocyanine and aluminium (diammine) octacarboxyphthalocyanine. The conjugates were prepared by conjugating aluminium octacarboxy phthalocyanine with potassium tetrachloro platinate to yield aluminium tetrakis and trikis (diaquaplatinum) octacarboxy phthalocyanine. The aluminium octacarboxy phthalocyanine was also conjugated with cis-diamminedichloroplatinum to yield aluminium bis and tris (diaquaplatinum) octacarboxy phthalocyanine. From the characterization of the conjugates it was discovered that the aluminium (diaquaplatinum) octacarboxy phthalocyanine had formed platinum nanoparticles with the Pc acting as a capping agent. The triplet lifetimes decreased with the increasing number of platinum complexesconjugated to the Pc. The heavy atom effect improved the overall photophysicochemical properties.

Novel lanthanide phthalocyanines containing dysprosium, erbium and lutetium as central metals were synthesized using phthalonitrile:metal salt ratio of 4:1 or lower phthalonitrile content as well as using unmetallated phthalocyanine. They were characterized using various spectroscopic and elemental analyses. Dysprosium bis-phthalocyanine was obtained while monomers were obtained for erbium and lutetium phthalocyanines. Theopen-shelldysprosiumbis-phthalocyanine and the monomeric complex of the open-shell erbium were neither fluorescent nor showed the ability to generate singlet oxygen. The triplet states of all the lutetium phthalocyanines were found to be populated with high triplet quantum yields and corresponding high singlet oxygen quantum yields. The fluorescence quantum yields of the lutetium phthalocyanines were however found to be very low. The lutetium phthalocyanines together with unsubstituted zinc phthalocyanine and its derivatives were successfully incorporated into electrospun polymer fibers either by covalent linkage or sorption forces. Spectral characteristics of the functionalized electrospun polymer fibers indicated that the phthalocyanines were bound and their integrity maintained within the fiber matrices. Most importantly the fluorescence and photoactivity of the phthalocyanines were equally maintained within the electrospun fibers. The functionalized electrospun polymer fibers especially those containing the zinc phthalocyanines could qualitatively detect nitrogen dioxide, a known environmental air pollutant. Also all the functionalized electrospun polystyrene and polysulfone fibers containing lutetium and zinc phthalocyanines could be applied for the photoconversion of 4-chlorophenol, 4-nitrophenol and methyl orange. Those of polystyrene could be re-used. Polyacrylic acid and polyurethane functionalized electrospun fibers were found not to be suitable for photocatalytic applications in aqueous medium. 4-Chlorophenol was found to be more susceptible to photodegradation while methyl orange very difficult to degrade.

he synthesis, extensive spectroscopic characterization and photophysical studies of low symmetry zinc phthalocyanine have been conducted. Comparisons have been made taking into consideration the influence of the solvent properties as well as substituent type and position. Photosensitizing properties of the zinc phthalocyanine derivatives in the presence of thiol capped CdTe quantum dots (QDs) were compared. The QDs were used as energy transfer donors and to facilitate with energy transfer through Förster resonance energy transfer (FRET) from the QDs to the MPcs. The linkage of unsymmetrically substituted 4-monoaminophenoxy zinc phthalocyanine (ZnAPPc) to CdTe quantum dots capped with mercaptopropionic acid (MPA), L-cysteine (L-cys) or thioglycolic acid (TGA) has been achieved using the coupling agents ethyl-N3 dimethylaminopropyl)carbodiimide (EDC) and N-hydroxy succinimide (NHS), which facilitate formation of an amide bond to form the QD-ZnAPPc-linked complex. The formation of the amide bond was confirmed using UV-Vis, Raman and IR spectroscopies, as well as AFM (atomic force microscopy). Förster resonance energy transfer (FRET) resulted in stimulated emission of ZnAPPc in both the linked (QDZnAPPc-linked) and mixed (QD:ZnAPPc-mixed) conjugates for MPA only. The linked L-cys and TGA complexes (QD-ZnAPPc-linked) gave the largest FRET efficiencies hence showing the advantages of covalent linking. Fluorescence quantum yields of QDs were decreased in QD:ZnAPPc-mixed and QD:ZnAPPc-linked. High triplet state quantum yields were obtained for the linked QD-phthalocyanine derivatives (ZnAPPc)and monoaminozinc phthalocyanine (ZnAPc) compared to when ZnAPPc and ZnAPc were mixed with MPA QDs without a chemical bond.

This thesis presents the study of the effects of CdTe-TGA quantum dots (QDs) on optical limiting ability of different phthalocyanine (Pc) complexes (5-12) containing Zn, Ga, In central metals and substituted with benzyloxyphenoxy, phenoxy, tertbutylphenoxy and amino groups in solution and in poly (methyl methacrylate) (PMMA) films. The optical limiting parameters of Pcs were higher for tertbutylphenoxy when compared to benzyloxyphenoxy and phenoxy substituents, in DMSO. Non-peripheral substitution decreased the optical limiting parameters. Third-order susceptibility (Im[χ⁽³⁾]/α) values of Pcs in the absence and presence of CdTe QDs were in the 10⁻¹² to 10⁻¹° esu cm range. Hyperpolarizabilities (γ) ranged from 10⁻³¹ to 10⁻²⁹ esu L for Pc alone or in mixture with QDs. The effect on the optical limiting abilities of twelve embedded phthalocyanines containing In, Ga, Zn and Al as central metals in polymer thin films was also examined. The effect of forming a covalent link zinc tetraamino phthalocyanine (12) with poly (methyl acrylic acid) (PMAA) and Zn (13) and OHAl (14) octacarboxy phthalocyanines to polyethylenimine (PEI) was also studied. The hyperpolarizability of the twelve phthalocyanines in polymer was found to be in the range of 10⁻²⁶ to 10⁻²⁴ esu.L. This is significantly higher than the hyperpolarizabilities of these phthalocyanines in solution. Non-linear optical (NLO) parameters were determined for phthalocyanine complexes containing In, Ga and Zn as central metals when embedded in PMMA polymer in the presence of quantum dots (QDs). The QDs mainly employed were CdTe-TGA (TGA = thioglylcolic acid). Triplet lifetimes increased as k (excited state (σex) to ground state (σg) absorption cross section ratio) values decreased with the addition of the CdTe-TGA to the phthalocyanines. The saturation energy density (Fsat) values were smaller in the films when compared to the solutions. Complex 7 tetrasubstituted with tert-butylphenoxy groups at non-peripheral positions was also studied in the presence of CdS-TGA, CdSe-TGA, fullerenes and single walled carbon nanotubes. There is a general improvement in optical limiting ability of Pc complexes in the presence of nanomaterials (NMs). Degradation studies seem to indicate that placing a phthalocyanine within a polymer thin film may protect it slightly from photo- and thermal degradation. 3(4), 15(16)-Bis-(4 -tert-butyl-phenoxy)-10, 22-diaminohemiporphyrazinato chloroindium hemiporphyrazine was synthesized from 1, 3, 5-triaminobenzene and 4-tert-butyl-phenoxyisoindoline. The structure of the complex was confirmed using mass, nuclear magnetic resonance and infrared spectroscopies. The nonlinear parameters of the compound was also analyzed in dimethylformamide and found to be significantly greater than previously analyzed phthalocyanines.

abstract: Development of efficient and renewable electrocatalytic systems is foundational to creation of effective means to produce solar fuels. Many redox enzymes are functional electrocatalysts when immobilized on an electrode, but long-term stability of isolated proteins limits use in applications. Thus there is interest in developing bio-inspired functional catalysts or electrocatalytic systems based on living organisms. This dissertation describes efforts to create both synthetic and biological electrochemical systems for electrocatalytic hydrogen production. The first part of this dissertation describes the preparation of three different types of proton reduction catalysts. First, four bioinspired diiron complexes of the form (μ-SRS)Fe(CO)3[Fe(CO)(N-N)] for SRS = 1,2-benzenedithiolate (bdt) and 1,3-propanedithiolate (pdt) and N-N = 2,2’-bipyridine (bpy) and 2,2’-bypyrimidine (bpym), are described. Electrocatatlytic experiments show that although the byprimidinal complexes are not catalysts, the bipyridyl complexes produce hydrogen from acetic acid under reducing conditions. Second, three new mononuclear FeII carbonyl complexes of the form [Fe(CO)(bdt)(PPh2)2] in which P2 = bis-phosphine: 4,5-Bis(diphenylphosphino)- 9,9-dimethylxanthene (Xantphos), 1,2-Bis(diphenylphosphino)benzene (dppb), or cis- 1,2-Bis(diphenylphosphino)ethylene (dppv) are described. All are functional bio-inspired models of the distal Fe site of [FeFe]-hydrogenases. Of these, the Xanthphos complex is the most stable to redox reactions and active as an electrocatalyst. Third, a molybdenum catalyst based on the redox non-innocent PDI ligand framework is also shown to produce hydrogen in the presence of acid. The second part of this dissertation describes creating functional interfaces between chemical and biological models at electrode surfaces to create electroactive systems. First, covalent tethering of the redox probe ferrocene to thiol-functionalized reduced graphene oxide is demonstrated. I demonstrate that this attachment is via the thiol functional groups. Second, I demonstrate the ability to use electricity in combination with light to drive production of hydrogen by the anaerobic, phototrophic microorganism Heliobacterium modesticaldum. / Dissertation/Thesis / Doctoral Dissertation Biochemistry 2017

abstract: Banded iron formations (BIFs) are among the earliest possible indicators for oxidation of the Archean biosphere. However, the origin of BIFs remains debated. Proposed formation mechanisms include oxidation of Fe(II) by O2 (Cloud, 1973), photoferrotrophy (Konhauser et al., 2002), and abiotic UV photooxidation (Braterman et al., 1983; Konhauser et al., 2007). Resolving this debate could help determine whether BIFs are really indicators of O2, biological activity, or neither. To examine the viability of abiotic UV photooxidation of Fe, laboratory experiments were conducted in which Fe-bearing solutions were irradiated with different regions of the ultraviolet (UV) spectrum and Fe oxidation and precipitation were measured. The goal was to revisit previous experiments that obtained conflicting results, and extend these experiments by using a realistic bicarbonate buffered solution and a xenon (Xe) lamp to better match the solar spectrum and light intensity. In experiments reexamining previous work, Fe photooxidation and precipitation was observed. Using a series of wavelength cut-off filters, the reaction was determined not to be caused by light > 345 nm. Experiments using a bicarbonate buffered solution, simulating natural waters, and using unbuffered solutions, as in prior work showed the same wavelength sensitivity. In an experiment with a Xe lamp and realistic concentrations of Archean [Fe(II)], Fe precipitation was observed in hours, demonstrating the ability for photooxidation to occur significantly in a simulated natural setting. These results lead to modeled Fe photooxidation rates of 25 mg Fe cm-2 yr-1—near the low end of published BIF deposition rates, which range from 9 mg Fe cm-2 yr-1 to as high as 254 mg Fe cm-2 yr-1 (Konhauser et al., 2002; Trendall and Blockley, 1970). Because the rates are on the edge and the model has unquantified, favorable assumptions, these results suggest that photooxidation could contribute to, but might not be completely responsible for, large rapidly deposited BIFs such those in the Hamersley Basin. Further work is needed to improve the model and test photooxidation with other solution components. Though possibly unable to fully explain BIFs, UV light has significant oxidizing power, so the importance of photooxidation in the Archean as an environmental process and its impact on paleoredox proxies need to be determined. / Dissertation/Thesis / Masters Thesis Biochemistry 2017

Processos de transferência de H+ de fotoácidos como piranina (POH) em vidros de SiO2, foram atribuídos à presença de água residual no gel. Nestes experimentos, o efeito devido à espécie básica do tampão (HPO4=), todavia não foi investigada. O entendimento de como as reações prototrópicas são mediadas no meio sólido e como a atividade do par ácido - base de Brönsted participa na transferência é o objetivo deste presente estudo. Questões como: o H+ difunde livremente através do gel? A espécie do tampão interage diretamente com o doador de H+, ou água é necessário para intermediar a transferência? Existe um teor limiar de água? Aqui são discutidas. A transferência de H+ da POH foi estudada em monólitos derivados da hidrólise ácida do TEOS contendo diferentes concentrações de tampão fosfato (condições iniciais Si: H2O 1: 16,5). A extensão da transferência de H+ é determinada pelo monitoramento da intensidade de fluorescência devido à base excitada (% PO-*) uma vez que a emissão surge da reação de transferência de H+. Nestes experimentos, géis foram preparados na ausência e presença de tampão fosfato. Até ~ 12 dias, um aumento na transferência de H+ é observada para todas as condições. É também verificado que o aumento na concentração de tampão é paralelo à extensão da reação. Em tempos muito curtos, a atividade da transferência de H+ relativamente baixa é devido à presença de ETOH (hidrólise do TEOS), o qual assim que o sistema envelhece é lixiviado junto com a água do gel. Depois deste envelhecimento inicial, aqueles géis contendo altas concentrações de tampão (50 e 250 mM) mostram uma atividade constante e os demais géis mostram uma queda na transferência de H+. No final do estágio, ~ 50 dias, os géis perderam aproximadamente 80% de sua massa, mas no gel final ainda existe quantia de água residual Si: H2O 1: 7. Com o intuito de explorar a atividade do tampão, misturas secas de KH2PO4 e K2HPO4 na proporção de pHaparente = 6,0 foram trituradas e secas e a fotoacidez do 2 - naftol (NOH) foi investigada. Claramente a baixo teor de água nenhuma reação é observada e somente a emissão devido a NOH* aparece (yem. = 345 nm), adição passo a passo de H2O é seguida pelo aumento na emissão a 413 nm, devido à forma básica (NO-*). Nesta condição, a concentração de água limiar é Xw = 0,44. Por outro lado, para o POH o limite de água para a transferência de H+ é Xw = 0,13. POH e NOH têm pKa no estado excitado (pKa*) de 0,5 e 3,0, respectivamente. Neste estudo, a atividade dos fotoácidos em meio sólido mostra ser dependente do pKa*, da concentração da espécie básica e do teor de água limiar. / H+ transfer processes in SiO2 glasses, from photoacids as piranine (POH), were assigned to the presence of residual water in the gel. In these experiments the effects due to the buffer basic species (HPO4=) were however not investigated. The understanding on how prototropic reactions are mediated in solid media and how the activity of Brönsted acid and base pairs participates in the transfer is the subject of the present study. Questions as: Does the H+ diffuse freely through the gel? Do the buffer species interacts directly with the H+ donors, or water is needed to intermediate the transfer? Is there a threshold in the water content? are here discussed. H+ transfer from POH was studied in monoliths derived from the acid hydrolysis of TEOS having varying concentrations of phosphate buffer (initial conditions Si : H2O 1:16.5). The extent of H+ transfer is determined by monitoring the fluorescence intensity due to the excited base (%PO-*) once this emission arises from the H+ transfer reaction. In these experiments gels were prepared in the absence and presence of phosphate buffer. Up to ~ 12 days an increase in H+ transfer is observed for all conditions. It is also found the increase in buffer concentration parallels the extent of reaction. At very short time the relatively low H+ transfer activity is due to the presence of ETOH (hydrolysis of TEOS), which as the systems age are lixiviated together with water from the gel. After this initial aging, those gels having high buffer concentrations (50 and 250 mM) show a leveled activity, the other gels show a decrease in H+ transfer. At the final stages ~ 50 days the gels lost around 80% of its mass, but in the final gel residual water still amounts to Si:H2O 1:7. In order to further exploit the buffer activity, \"dry\" mixtures of KH2PO4 and K2HPO4 in proportions to pHapp = 6.0 were grinded and dried and the photoacidity of 2-naphtol (NOH) were investigated. Clearly at low water contents no reaction is observed and only the emission due to the NOH* appears (yem = 345 nm), addition step by step of H2O is followed by an increase in the emission at 413 nm, due to the basic form (NO-*). In this situation the threshold water concentration is around Xw = 0.44. By other hand for POH the threshold water for H+ transfer is Xw = 0.13. POH and NOH have excited state pKa\'s (pKa*) of 0.5 and 3.0, respectively. In this study the activity of photoacids in solid media is shown to be dependent on pKa*, on the concentration of basic species and of a threshold water content.

abstract: Photosynthesis, one of the most important processes in nature, has provided an energy basis for nearly all life on Earth, as well as the fossil fuels we use today to power modern society. This research aims to mimic the photosynthetic process of converting incident solar energy into chemical potential energy in the form of a fuel via systems capable of carrying out photo-induced electron transfer to drive the production of hydrogen from water. Herein is detailed progress in using photo-induced stepwise electron transfer to drive the oxidation of water and reduction of protons to hydrogen. In the design, use of more blue absorbing porphyrin dyes to generate high-potential intermediates for oxidizing water and more red absorbing phthalocyanine dyes for forming the low potential charge needed for the production of hydrogen have been utilized. For investigating water oxidation at the photoanode, high potential porphyrins such as, bis-pyridyl porphyrins and pentafluorophenyl porphyrins have been synthesized and experiments have aimed at the co-immobilization of this dye with an IrO2-nH2O catalyst on TiO2. To drive the cathodic reaction of the water splitting photoelectrochemical cell, utilization of silicon octabutoxy-phthalocyanines have been explored, as they offer good absorption in the red to near infrared, coupled with low potential photo-excited states. Axially and peripherally substituted phthalocyanines bearing carboxylic anchoring groups for the immobilization on semiconductors such as TiO2 has been investigated. Ultimately, this work should culminate in a photoelectrochemical cell capable of splitting water to oxygen and hydrogen with the only energy input from light. A series of perylene dyes bearing multiple semi-conducting metal oxide anchoring groups have been synthesized and studied. Results have shown interfacial electron transfer between these perylenes and TiO2 nanoparticles encapsulated within reverse micelles and naked nanoparticles. The binding process was followed by monitoring the hypsochromic shift of the dye absorption spectra over time. Photoinduced electron transfer from the singlet excited state of the perylenes to the TiO2 conduction band is indicated by emission quenching of the TiO2-bound form of the dyes and confirmed by transient absorption measurements of the radical cation of the dyes and free carriers (injected electrons) in the TiO2. / Dissertation/Thesis / Ph.D. Chemistry 2013

A amicarbazona constitui-se em um herbicida do grupo das triazolinonas, desenvolvida para substituir a atrazina no mercado mundial. Diversas tecnologias têm sido estudadas objetivando a remoção de pesticidas de efluentes aquosos, procurando estudar os mecanismos de degradação envolvidos e o grau de toxicidade dos fotoprodutos gerados. Neste sentido, este trabalho tem como objetivo principal o estudo de degradação do princípio ativo amicarbazona, em solução aquosa, por fotólise direta, propondo estruturas químicas de produtos de transformação em um estudo teórico-fundamental. Foram avaliados parâmetros como concentração de herbicida, pH do meio reacional, concentração de oxigênio dissolvido, concentração de nitrato e de isopropanol como supressor de radicais livres. Dentre os parâmetros avaliados no processo de fotólise, o valor do pH do meio reacional influencia consideravelmente o mecanismo de fotodegradação do herbicida amicarbazona, favorecendo ou desfavorecendo a formação de determinado intermediário. Verificou-se que a molécula de amicarbazona gera como produto de degradação primário a molécula de amicarbazole, principalmente em meio ácido, como resultado de mecanismo de deaminação. Por sua vez, a utilização de processo UV/H2O2 foi capaz de proporcionar degradação completa da amicarbazona em tempo reacional máximo de 60 minutos. Contudo, mesmo com a utilização de agente oxidante auxiliar, não houve mineralização completa da amicarbazona, havendo 58% de redução de carbono orgânico dissolvido na melhor condição experimental estudada. / Amicarbazone is a triazolinone herbicide developed to substitute atrazine in the world market. Several technologies have been studied aiming at the removal of pesticides from wastewater, seeking to study the degradation mechanisms involved and the degree of toxicity of the photoproducts formed. In this context, the main goal of this work is to study the degradation of amicarbazone in aqueous solution by direct photolysis, suggesting possible chemical structures for the transformation products according to a theoretical and fundamental approach. Parameters such as herbicide concentration, pH, dissolved oxygen concentration, nitrate concentration, and propan-2-ol as a free radical scavenger were considered. Among the parameters studied in the photolysis process, the pH showed influence on the photochemical mechanism of amicarbazone degradation, favoring or not the formation of particular intermediates. It was found that the photolysis generates amicarbazole as the primary degradation product in acidic medium as a result of the deamination mechanism. The use of UV/H2O2 process enabled the complete degradation of amicarbazone in a reaction time of 60 minutes at most. However, even with the use of the auxiliary oxidant reactant, the complete mineralization of amicarbazone was not achieved, with 58% reduction of dissolved organic carbon in the best experimental condition studied.