Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2016-04-20T18:45:25Z No. of bitstreams: 2 Dissertaçao - Leandro Rezende Franco- 2016.pdf: 12911790 bytes, checksum: 424add978f6ebc12f99143d7bb1c924f (MD5) license_rdf: 19874 bytes, checksum: 38cb62ef53e6f513db2fb7e337df6485 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-04-25T14:29:50Z (GMT) No. of bitstreams: 2 Dissertaçao - Leandro Rezende Franco- 2016.pdf: 12911790 bytes, checksum: 424add978f6ebc12f99143d7bb1c924f (MD5) license_rdf: 19874 bytes, checksum: 38cb62ef53e6f513db2fb7e337df6485 (MD5) / Made available in DSpace on 2016-04-25T14:29:50Z (GMT). No. of bitstreams: 2 Dissertaçao - Leandro Rezende Franco- 2016.pdf: 12911790 bytes, checksum: 424add978f6ebc12f99143d7bb1c924f (MD5) license_rdf: 19874 bytes, checksum: 38cb62ef53e6f513db2fb7e337df6485 (MD5) Previous issue date: 2016-02-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The combined use of the Sequential QM/MM method with the ASEC mean field approximation [1] and the Free Energy Gradient method [2] has been very successful in describing the electronic structure of molecules in solution [3]. The advantage of this combination is that it permits the usage of an atomic- level modeling of the whole system, in contrast to continuum models, and, at the same time, it is less computationally expensive than ab initio or QM/MM simulations, even allowing the employment of more sophisticated electronic structure methods. In this context, the present work deals with the study of conformational and electronic structure, in solvent medium, of two organic compounds, DMACA and Phenol Blue, which have in common the characteristic of having acceptor-donor groups. The study is conducted in the presence of nonpolar, polar protic and polar aprotic solvents. It is adopted as basic methodology the ASEC-FEG, but also it is made a study with a continuum method, namely PCM. The results show that the solvent effect causes a significant geometric distortion of the molecules of interest while causing an internal charge displacement from donor group to acceptor group. Both effects are more pronounced in protic and aprotic solvents but mainly in protic solvents, in which hydrogen bonds lead to a greater solute polarization. The absorption spectra of these molecules, calculated by TD-DFT (CAM-B3LYP), directly reflect these changes. For all solvents, the absolute values of electronic transitions and their respective solvatochromic shifts are in good agreement with the experimental results. / O uso combinado de métodos QM/MM sequencial com uma aproximação de campo médio (ASEC) [1] e o método do Gradiente de Energia Livre [2] tem tido sucesso na descrição da estrutura eletrônica de moléculas em solução [3]. Uma das vantagens dessa combinação é que ela permite o tratamento do sistema soluto-solvente em um nível atomístico, em contraste com modelos contínuos, e tem a vantagem de, ao mesmo tempo, ser uma metodologia menos cara computacionalmente do que simulações QM/MM ab initio [4]. Nesse contexto, o presente trabalho versa sobre o estudo da estrutura conformacional e eletrônica, em meio, de dois compostos orgânicos, DMACA e Phenol Blue, que tem em comum a característica de possuir grupos aceitador e doador de elétrons. O estudo é realizado na presença de solventes apolares, polares apróticos e polares próticos. Adota-se como metodologia básica o método QM/MM sequencial utilizando o ASEC, mas faz-se também um estudo com um método contínuo conhecido, o PCM. Os resultados mostram que o efeito de solvente provoca uma signifativa reestruturação geométrica das moléculas de interesse, ao mesmo tempo em que causa um deslocamento interno de carga do grupo doador para o grupo aceitador. Os dois efeitos são mais pronuciados em solventes apróticos e próticos, mas principalmente nos solventes próticos, em que as ligações de hidrogênio levam a uma maior polarização do soluto. Essas mudanças refletem diretamente no espectro de absorção, calculado por TD-DFT (CAM-B3LYP), dessas moléculas. Dos meios apolares, passando pelos polares apróticos, indo até os polares próticos, os valores absolutos das transições eletrônicas e seus respectivos deslocamentos solvatocrômicos encontram-se em bom acordo com os resultados experimentais.

The present thesis entitled, "Molecular expression through fluorescence: Studies in probe design and aggregation" describes very simple bi-functional donor-acceptor poly-aromatic fluorophores that have been shown to possess distinctive properties depending on the context in which they are studied. In a sense, this work is an effort in exemplifying the inherent diversity and power of "molecular expression", with the central theme here being the phenomenon of fluorescence. The work has been divided into four chapters, each having a self-contained introduction. Chapter 1: First instance of metal ion (Zn2+) sensing exclusively at amphiphilic interfaces. (1 -pyrenyl)rnethyl-bis- [(2-pyridyl)methyl]amine (Pybpa), a simple, bi-functional fluorophore was synthesized. Pybpa has the modular design of a photoinduced electron transfer (PET) based analyte sensor. In Pybpa, a photoinduced electron transfer (PET) operates from the pyrenyl nitrogen (PyCH2-iV) to the excited pyrenyl (Py*) chromophore leading to fluorescence quenching. Zn2+ ion binding to the bis-picolyl (bpa) unit of Pybpa stops the PET process and leads to fluorescence enhancement. Thus Pybpa was able to sense Zn2+" in organic solvents. In water, however, Pybpa showed pronounced aggregation and the probe did not sense any metal ion. Surfactant micelles provide hydrophobic regions in water and the dynamic rnicellar assemblies could disrupt Pybpa aggregates. Pybpa monomers solubilized in micelles were responsive to Zn2+ in the low micro molar concentration range. The metal ion sensing on micelles was reflective of the charge of the interface. The sensing is negligible on cationic surface (CTAB), moderate on negatively charged surface (SDS micelles) and is the most efficient on neutral interface provided by TWEEN-20 micelles. With the Pybpa 'sensor*, no sensing is possible in water and hence the sensing is exclusive to the interface. Pybpa doped in membranous aggregates like phosphatidylcholine (PC) lipid bilayers, exists in monomeric form, and was able to sense Zn . The sensing on phosphatidylcholine (PC) bilayer vesicles was found to depend on the fluidity of the membrane. Zn2^ sensing with interfacially bound probe "was extended to a globular protein bovine serum albumin (BSA). BSA, a carrier protein, can bind hydrophobic molecules as well as metal ions like Zn2f. BSA was shown to disrupt Pybpa aggregation and bind Pybpa in a facile manner. BSA bound Pybpa was able to sense externally added Zn2+. Biological sensing of trace amounts of Zn2+ has been considered important since Zn2+ is crucial for eukaryotic systems. This is the first example of such 'exclusive' interfacial sensing of a metal ion. Chapter 2: Towards understanding and modulating self-assembly of pyrenyl bis-picolyl a mine: Organic nanoparticles that show tunable emission. Pybpa was found to aggregate in water in the size range of 80-250 nm. Evidence of aggregation was seen at concentrations as low as 1 |iM. The nanoscopic particles formed were characterized through transmission electron microscopy (TEM) and dynamic light scattering (DLS). Pybpa in water showed dual emission bands, with one band resernhling the emission from 'monomeric' Pybpa (as seen in solutions in organic solvents) and a broad red-shifted emission band (A,max ~ 480 ran) designated as "aggregate/nanoparticle" emission. Distinct excitation spectra for the two emission bands indicate that the bands (the '390 nm' band and the '480 nm' band) originate through distinct excitation/emission channels. The time resolved emission decay for the 'monomer' emission (397 nm) showed a substantial contribution from a long-lived pyrene-like excited state (x = 103.9 ns, 40% relative amplitude). On the other hand, the decay at 475 nm (for the nanoparticle/aggregate emission band) was considerably faster, with no evidence of any pyrene-like long-lived state. The short lifetimes indicated an exciplex nature of the red-shifted emission band, X-,nax~480 nm. The effect of temperature and urea on these aggregates was examined. The nanoparticles formed even in a concentrated urea solution (7.8 M). The aggregates formed in urea were found to be more emissive, indicating a 'looser' aggregate with reduced fluorescence quenching. Similar results were obtained on heating the aggregate. Increasing the concentration of Pybpa in water causes a change in the nature of the colloids formed as exemplified by increase in aggregate size and a decrease in the polydispersity index. Also seen was a substantial red shift in the 'aggregate emission'. At higher concentrations, the presence of three independent excitation/emission channels was observed. It is likely that a new type of aggregated Pybpa species formed at higher concentration, which emits at longer wavelength (A,rnax~540 nm), In such a scenario, it is possible to tune the emission wavelength by the choice of appropriate wavelength of excitation. Further, there is an opportunity to tailor the emission properties by controlling the aggregation behavior. The modulation of emission is one of the primary goals of research on fluorescent organic nanoparticles. Chapter 3: Photophysical properties of aryl-terpyridines in solution, solid and aggregated state: Unique CT emission from nanoparticles in water. Two aryl terpyridines, 4T-(l-pyrenyl)-2,2l:6'52fl-terpyridine (Pytpy) and 4'-(9-anthryl)-2,2':6',2n-terpyridine (Antpy), where the fluorophoric pyrene or anthracene unit is directly coupled to the terpyridine unit, were synthesized. The aryl terpyridines conjugates can be viewed as donor-acceptor molecules that are conformationally labile, with the possibility of rotation around three single bonds. It was of interest to see as to how conformational effects express themselves in different environments, especially in relation to the possibility of charge separation. Crystal structure data and Serni-empirical AMI calculations revealed a twisted molecular conformation for each of the molecules. Absorption and emission (steady state as well as tirne-resolved) behavior of Pytpy and Antpy in various organic solvents have been presented. The molecules showed only limited conjugation between the two units in the absorption behavior with the degree of conjugation being greater for Pytpy. In the emission behavior, only a single emission band (with a single lifetime) was observed in all organic solvent. Steady state and time resolved fluorescence data suggest the existence of a mixed or coupled, largely 7t—7i* state, with only marginal charge separation. The various photophysical parameters have been determined for the two systems. It appears that in the excited state, the inesomeric interactions show an increase for each of the two aryl-terpyridines, indicating at least a partially planar geometry in the excited state. Some specific solvent effects were observed for the molecules in alcoholic solvents and there was evidence of excited state H-bonding occurs for the aryl terpyridines in polar protic organic solvents, especially methanol. Pytpy and Antpy self-assembled in water over a large concentration range (1-100 |xM) to form spherical nanoparticles in the size range of 150-200 nm, as characterized by TEM and DLS. The absorption spectra for both conjugates showed red shift of the absorption bands in water (-10 nrn) along with significant tailing of the long-wavelength bands. The change in emission behavior in going from solution to the aggregates in water was very dramatic. Multiple, broadened, highly red-shifted emission bands for both Antpy and Pytpy were observed. Quite significantly, a long lifetime component in the emission decay was shown by the conjugates in water as compared to the lifetimes observed in solution. The data points towards a unique CT emission for Antpy and Pytpy aggregates in water. The excitation spectra for the multiple emission bands seen for Pytpy (or Antpy) were observed to be identical. Thus a single ground state population is responsible for emission over the entire range (approximately 420 nin - 600 nm). The existence of multiple emission bands and the large bathochromic shifts are exclusively due to excited state effects in the aggregated state in water. It appears that excited state H-bonding of the tpy N with water helps facilitate the excited state CT. The solid-state behavior of Pytpy and Antpy lias been examined and the emission from the two crystalline solids is very distinct. Antpy emission showed a X,,nax at -430 nm while Pytpy emission peaked at ~ 560 nm. The difference in the solid-state emission behavior exhibited by Pytpy and Antpy is explained through a consideration of the crystal packing for the two molecules. The degree of n-facial stacking was observed to be much greater for Pytpy. The observation of the distinct packing and emission shown by solid Pytpy and Antpy is highly significant if one considers the identical emission shown by the aqueous nanoparticles of the two molecules and brings to fore the 'nanoparticle effect' in water as compared to a simple concentration effect. It was also demonstrated that it was possible to modulate the aggregation of the terpyridines through additives, like metal ions Chapter 4: Pyrenyl terpyridine as a ratiometric fluorescence probe for sensing order and polarity of membranous aggregates. Pytpy was examined for its utility in probing surfactant aggregates, particularly membranous assemblies. la lipid bilayer vesicles made of phosphatidylcholine (PC) lipids (like dimyristoyl phosphatidylcholine, DMPC or egg-yolk PC) Pytpy showed an emission profile with marked similarity to that shown by the probe in water. Specifically, a broad red-shifted emission with A,maxin. the 500 nm region was observed. In addition, a peak in the -420 nm region was also seen. Fluorescence anisotropy was used to confirm the presence of vesicle-bound probe. Excitation spectra confirmed the presence of two distinct probe populations, om responsible for the '420 nm9 emission and another population responsible for the multiple, red-shifted emission bands. The emission behavior was indicative of aggregation of Pytpy on the vesicle surface and CT effects operating in conjunction with H-bonding. Fluorescence lifetime measurements, carried out at different Is suggest the CT nature of the red-shifted emission. The aggregation of the probe on the bilayer interface was confirmed by concentration and temperature dependence of the emission profile. The role of water in stabilizing this CT emission on bilayer surfaces was shown with use of a surface dehydrating agent polyethylene glycol (PEG). All these results helped build a model for the behavior of Pytpy in water. Pytpy aggregates on bilayer surface and shows a red-shifted CT emission with stabilization by interfacial water. Thus, the Pytpy 'aggregate' has a shallow, water accessible location in the bilayer. In addition to this, there is another Pytpy population responsible for the emission in the 420 nm region, and this second population might have a comparatively deeper location. The wavelength of the CT emission was sensitive to the polarity of the interface as evidenced "by the results obtained with bilayers made of a number of PC lipids. In general, the X™ax of the CTband showed a red shift with increasing polarity. The increase in polarity also caused an increase in the average lifetime of the probe. Pytpy could distinguish between vesicles made of lipids of different head groups. Aggregates made of phosphatidylethanolamine (PE) head group are in general less hydrated than PC lipid assemblies and Pytpy emission reflected this when examined in vesicles made of related lipids (dioleoyl lipids, DOPC and DOPE; dirnyristoyl lipids, DMPC and DMPE). Pytpy emission from PE vesicles was quenched and showed a pronounced blue shift in the emission Xmax vis-a-vis PC bilayers. Thus, dehydration of the interface consistently led to the destabilization of the CT state. Further, Pytpy emission was also responsive to hydration in more complex mixed PC-PE assemblies. Pytpy emission "behavior was also used to probe fluidity in complex "mixed" lipid assemblies- The effect of cholesterol on DMPC bilayers in terms of its known ability to dehydrate the bilayer was reported through a blue-shift Xmax of CT emission band. Further, cholesterol also causes drastic change in the bilayer at concentrations greater than ~ 30 mol%. This change in the bilayer was sensed through a sudden reduction in fluorescence intensity. Also from a careful analysis of Pytpy in various PC and PE vesicles, it emerged that the more fluid aggregates showed larger quantum yields. Thus, Pytpy could simultaneously report on both the polarity and fluidity of lipidic aggregates. Pytpy could also provide information about the order of an assembly. While the probe aggregated in bilayers and other membranous assemblies and showed water assisted CT emission, in more dynamic assemblies like micelles, Pytpy aggregates were not sustained, Pytpy in micelles showed emission spectra very similar to that seen in solutions in aprotic organic solvents. Thus, Pytpy proved to be a very useful ratiometric sensor for vesicle-to-rnicelle transition. Also, it has been possible to study some surfactant-lipid mixed assemblies that show phase separation. Pytpy reported the formation of a 'rigid', bilayer-like phases in mixed assemblies that are called bicelles.

The thesis entitled “New Supramolecular Ion Sensing Probes and their Application in the Detection of Environmentally Relevant Ions” deals with the design and synthesis of several small molecular probes which can specifically sense environmentally relevant ions of (anion or cation) particularly in aqueous or biological medium. The probes have been designed using four different molecular entities which include anthraquinone, oxidized bis-indolyl system, pyrene and rhodamine. The probes afford naked eye detection of a particular ion in the aqueous medium. This work has been divided into six chapters. Chapter 1. Introduction The first chapter gives a brief idea of ion sensor. It provides the description of various approaches used for designing molecular sensors. The chapter further presents an overview of the four different dyes (anthraquinone, oxidized-bis-indole, pyrene and rhodamine) used for designing probes in this work. The properties of these probes, their advantages and disadvantages to use as a signaling subunit have been discussed. This chapter also describes the use of micellar medium for solubilizing different organic dyes in water. Chapter 2. Colorimetric Probes based on Anthraimidazolediones for Selective Sensing of Fluoride and Cyanide ion via Intramolecular Charge Transfer. The second chapter describes the design and synthesis of four different probes based on anthra [1, 2-d] imidazole-6, 11-dione. The anthraquinone part of each molecule has an acceptor moiety whereas substituted nitrogen linked aromatic unit forms the donor site. Each probe acted as strong colorimetric sensor for fluoride and cyanide ion detection and exhibited intramolecular charge transfer (ICT) band which showed significant red-shifts after addition of either the F¯ or CN¯ ion. One of the probes 2 showed selective colorimetric sensing for both cyanide and fluoride ions. In organic medium 2 showed selective color change with fluoride and cyanide, whereas in aqueous organic medium it showed a selective ratiometric response towards cyanide ion. The effect of anionic charge (on the donor moiety) on ICT has been discussed. Among the various donor moieties, the donor site having negative charges on them was found to disperse greater electron density on them. Figure 1. Molecular structures of the sensors Chapter 3 deals with chemodosimetric detection of cyanide ion in water using various oxidized bis-indole based compounds. Chapter 3A. A Chemodosimetric Probe based on a Conjugated and oxidized Bis¬ indolyl System for Selective Naked Eye Sensing of Cyanide ion in Water. The chapter 3A describes the design and synthesis of a new water-soluble bis-indolyl based probe, 5 which possesses two –COOH groups. This probe specifically reacted with the CN¯ ion in pure water at ambient temperature and produced a remarkable change in color from red to colorless. The mechanism of this process was investigated by NMR (1H, 13C and DEPT-135) spectroscopy, mass spectrometry and kinetic studies. The mechanism investigation showed that the cyanide ion reacts with the probe and removes the conjugation of the bis-indolyl moiety of the probe with that of the 4-substituted aromatic ring which renders the probe colorless. Taken together a plausible mechanism of the reaction was presented which showed to operate via a Michael type adduct formation under ambient conditions of pH and temperature in water. The probe gave a detection limit of 0.38 ppm for detection of cyanide ion in water. Figure 2. Molecular structure of the probe 5. Chapter 3B. Micelle Assisted ppb level Detection of Cyanide ion in Water by Chemodosimetry and Visual detection of the Endogenous Cyanide. The chapter 3B deals with the synthesis of a bis-indole based colorimetric probe 6. The probe showed selective detection of the cyanide ion in water at ppb level and a visible detection of endogenous cyanide from cassava (a major staple food in the developing world) by chemodosimetry. The cyanide ion binds with the probe 6 in a chemodosimetric fashion and follows pseudo first-order kinetics in water under appropriate conditions. It showed a highly sensitive detection of the cyanide ion in water with a detection limit of 0.33 ppm. The use of the micellar medium improved the detection limit drastically and a ppb level detection limit was achieved. The probe also showed the detection of the endogenously bound cyanide in cassava both visually and by spectrophotometer. Figure 3. Molecular structure of the probe 6. Chapter 3C. Ratiometric Cyanide ion probe in Water and for the detection of the Endogenously bound cyanide. Chapter 3C presents the synthesis of two new bis-indolyl (7 and 8) based probes for colorimetric detection of cyanide ion in pure water. Compound 8 showed a ratiometric response with cyanide in water and a visual detection of the endogenously bound cyanide ion in cassava. Using compound 8 the selective detection of the cyanide ion in water was achieved with a detection limit of ~ 17 ppb which is almost 13 times lower than the permitted limit as specified by EPA, United States. 7; R = H 8; R = -(OCH2CH2)3CH3 Figure 4. Molecular structures of the probes 1 and 2. Chapter 4 deals with the colorimetric and ratiometric detection of the Cu2+and Hg2+ions using different small synthetic molecular probes. Chapter 4A. Colorimetric Sensors for Ratiometric Detection of Copper and Mercury ions in Biological media and below ppm level in Water. The chapter 4A deals with the synthesis of two novel colorimetric probes (9, 10) using bispicolyl unit as the binding moiety and anthraimidazolediones and bis-indolyl system as a signaling sub-unit. Using the two sensors, Cu2+ion can be detected below the permitted limit (1.3 ppm) in both drinking water and at physiological pH 7.4. Sensor 9 can detect both Cu2+and Hg2+ in water with very low detection limit. It showed specific binding with Cu2+ at physiological pH 7.4 and in presence of serum albumins. Chemosensor 10 can be used for the specific detection of both Cu2+and Hg2in water as well as for the contamination in microorganisms. Figure 5. Molecular structure of the sensors 9 and 10. Chapter 4B. A New Molecular Probe for the Selective Sensing of Cu2+ and Hg2+ ions in Micellar Media and in Live ells.This chapter describes a synthesis of a novel bispicolyl based sensor 11 which can detect Cu2+ ion specifically in water medium and both Cu2+ and Hg2+ ions selectivelyin Brij-58 micellar medium. In micellar medium both the ions can be detected in the ppb level. Using fluorescence spectroscopy these two metal ions can be discriminated.The probe is also be useful for checking metal ion contamination in cellular samples. Figure 6. Molecular structure of the sensor 11. Chapter 4C. Rhodamine based Sensors for Cu2+ and Hg2+ ions in Water and in Biological media. The chapter 4C presents the synthesis and the sensing properties of the three positional isomers of the pyridine end of the rhodamine-pyridine compounds (12-14). The three isomers only differ in the position of nitrogen of the pyridine moiety. Sensor 12, which contains the pyridine nitrogen at the ortho-position showed selective sensing toward Cu2+ ion in both pure water and in buffered physiological media of pH 7.4. It gave a detection limit of ~13 ppb which is 100 times lesser than the EPA permitted limit. The other two sensors 13 and 14, which possessed the pyridine ends with the nitrogen atom at the meta- and the para- positions respectively showed the selective sensing of Hg2+ ion in water and did not show any interaction with the Cu2+ ion. Probes 2 and 3 showed ‘turn-on’ detection of Hg2+ ion both in the UV-vis and the fluorescence emission spectroscopy. Compound 2 and 3 showed a detection limit of ~ 9 and 4 ppb respectively. The NMR titration showed the change in color was due to the opening of the spirolactam ring of the rhodamine. The sensors can also be used for the detection of Cu2+ and Hg2+ ion in real life water samples and in the live cells. Figure 7. Molecular structure of the sensors 12, 13 and 14. Chapter 5. Ratiometric and ppb level Detection of Toxic Transition Metal ions using a Single Probe in Micellar media. This chapter describes the selective sensing of multiple ions using a single probe 15. The probe incorporates pyrene and pyridine as signaling and interacting moiety respectively. The sensor showed different responses towards different metal ions just by varying the medium of detection. In organic solvent (acetonitrile), the probe showed selective detection of Hg2+ ion. In water the fluorescence quenching was observed with three metal ions, Cu2+, Hg2+ and Ni2+. Further just by varying the surface charge of different micellar media, the probe showed selective interaction with Hg2+ ion in neutral micelles (Brij-58). However, in anionic micellar medium (SDS), the probe showed selective changes with both Cu2+ and Ni2+ in the UV-vis spectroscopy. The discrimination between these two ions was achieved by emission spectroscopy, where it showed selective quenching only with Cu2+. Thus using a single probe all the three metal ions Cu2+, Hg2+ and Ni2+ can be detected and discriminated just by varying the surface charge of the micellar medium. Figure 8. Molecular structure of the sensors 15. Chapter 6. Highly sensitive Rhodamine Based Dual Probes for the Visual detection of F¯ and Hg2+ ions in Water. This chapter deals with the design and synthesis of two new rhodamine based probes (16-17) which act as dual probes for the ppb level selective detection of Hg2+ and F¯ ions in water and at physiological pH 7.4. The two probes were synthesized by coupling tert-butyldiphenylsilyl (TBDPS) protected forms of 4-hydroxybenzaldehyde and 2, 4- dihydroxy benzaldehyde with rhodamine hydrazone. The F¯ ion detection is based on the desilylation of the probe, whereas the spirolactam ring opening leads to the detection of Hg2+ ion. The two probes gave turn-on detection of both Hg2+ and F¯ ion selectively in aqueous medium with the detection limit well below the EPA permitted limits. The probes showed detection of both the ions by dual mode with visibly different color and fluorescence under UV-lamp. The F¯ ion interacts with the silyl bond of probe and the cleavage results into yellow color whereas; the addition of Hg2+ ion to the probe solution opened the spirolactam ring and resulted into appearance of pink color. Figure 9. Molecular structure of the probes 16 and 17. (For structural formula pl see the abstract file)

Neste trabalho, descreve-se a síntese, caracterização e propriedades dos complexos derivados da tetra(3,4-piridil)porfirazina com os grupos [Ru(bipy)2Cl]1+. A conjugação eletrônica entre o resíduo piridínico e o anel da porfirazina promovem uma eficiente comunicação entre os grupos periféricos e o central, que é refletido no espectro de emissão e seu correspondente perfil de excitação. Esse tipo de comportamento revela um efeito antena no sistema H2TPyPzTRu, contrastante com as propriedades fotofisicas das porfirinas análogas TPyPRu, onde os grupos piridínicos exibem baixa interação eletrônica ao anel porfirínico. Apesar do forte acoplamento eletrônico entre os grupos perféricos e o central, as propriedades eletrônicas dos complexos de rutênio foram preservadas, exibindo potenciais redox muito próximos dos complexos livres e comportamento espectroeletroquímico típicos de complexos metálicos N-heterocíclicos. Esses aspectos levam a novas perspectivas relacionadas à estrutura dos compostos, pois são potencialmente interessantes para o estudo referente à formação de oxigênio singlete e para PDT. Outro direcionamento desta tese, foi o de explorar a geração de novas interfaces baseadas na formação de pares iônicos constituídos pelas espécies H2TPyPzTRu/CuTSPc em comparação com o filme da espécie catiônica H2TPyPzTRu. Através de medidas de espectroscopia de impedância eletroquímica, foram constatados mecanismos distintos de condução nos filmes formados, que pode ser ou um mecanismo misto envolvendo os complexos periféricos e o anel central da porfirazina, ou um mecanismo de condução eletrônica envolvendo somente o sistema de empilhamento π do anel central da porfirazina. / In this work, we describe the synthesis, characterization and properties of derived tetra(3,4-pyridil)porphyrazine complex containing four [Ru(bipy)2Cl]1+ groups. The electronic conjugation between the pyridinium moiety and the porphyrazine ring promote an efficient communication between the peripherical groups and central ring, which is reflected in the emission spectrum and related excitation profile. The observed behavior reveals an efficient antenna effect in the H2TPyPzTRu system. ln spite of the strong electronic coupling between the central and peripherical groups, the electronic properties of ruthenium complex were preserved, exhibiting redox potencials very close to those of free complexes. These aspects provided new perspectives of exploiting the compound strutures, particularly the oxygen singlet formation and PDT application. Another aspect focused in this investigation was the generation of new interfaces based on ion-pair formation of H2TPyPzTRu/CuTSPc, in comparison with its cationic species H2TPyPzTRu alone. By means of electrochemical impedance spectrocopy, it was shown that the conduction mecanisms in these films involve either the peripherical complex and the central porphyrazine ring.

Neste trabalho, descreve-se a síntese, caracterização e propriedades dos complexos derivados da tetra(3,4-piridil)porfirazina com os grupos [Ru(bipy)2Cl]1+. A conjugação eletrônica entre o resíduo piridínico e o anel da porfirazina promovem uma eficiente comunicação entre os grupos periféricos e o central, que é refletido no espectro de emissão e seu correspondente perfil de excitação. Esse tipo de comportamento revela um efeito antena no sistema H2TPyPzTRu, contrastante com as propriedades fotofisicas das porfirinas análogas TPyPRu, onde os grupos piridínicos exibem baixa interação eletrônica ao anel porfirínico. Apesar do forte acoplamento eletrônico entre os grupos perféricos e o central, as propriedades eletrônicas dos complexos de rutênio foram preservadas, exibindo potenciais redox muito próximos dos complexos livres e comportamento espectroeletroquímico típicos de complexos metálicos N-heterocíclicos. Esses aspectos levam a novas perspectivas relacionadas à estrutura dos compostos, pois são potencialmente interessantes para o estudo referente à formação de oxigênio singlete e para PDT. Outro direcionamento desta tese, foi o de explorar a geração de novas interfaces baseadas na formação de pares iônicos constituídos pelas espécies H2TPyPzTRu/CuTSPc em comparação com o filme da espécie catiônica H2TPyPzTRu. Através de medidas de espectroscopia de impedância eletroquímica, foram constatados mecanismos distintos de condução nos filmes formados, que pode ser ou um mecanismo misto envolvendo os complexos periféricos e o anel central da porfirazina, ou um mecanismo de condução eletrônica envolvendo somente o sistema de empilhamento π do anel central da porfirazina. / In this work, we describe the synthesis, characterization and properties of derived tetra(3,4-pyridil)porphyrazine complex containing four [Ru(bipy)2Cl]1+ groups. The electronic conjugation between the pyridinium moiety and the porphyrazine ring promote an efficient communication between the peripherical groups and central ring, which is reflected in the emission spectrum and related excitation profile. The observed behavior reveals an efficient antenna effect in the H2TPyPzTRu system. ln spite of the strong electronic coupling between the central and peripherical groups, the electronic properties of ruthenium complex were preserved, exhibiting redox potencials very close to those of free complexes. These aspects provided new perspectives of exploiting the compound strutures, particularly the oxygen singlet formation and PDT application. Another aspect focused in this investigation was the generation of new interfaces based on ion-pair formation of H2TPyPzTRu/CuTSPc, in comparison with its cationic species H2TPyPzTRu alone. By means of electrochemical impedance spectrocopy, it was shown that the conduction mecanisms in these films involve either the peripherical complex and the central porphyrazine ring.