A library of variously-substituted dipyrrins and their first-row transition metal (Mn, Fe, Cu, Zn) complexes have been synthesized, and the effects of peripheral substituents on the spectroscopic, electrochemical, and structural properties of both the free-base dipyrrins and their metal complexes has been explored. The optical and electrochemical properties of the free dipyrrins follow systematic trends; with the introduction of electron-withdrawing substituents in the 2-, 3-, 5-, 7-, and 8-positions of the dipyrrin, bathochromic shifts in the absorption spectra are observed, oxidation becomes more difficult, and reduction becomes more facile. Similar effects are seen for iron(II) dipyrrinato complexes, where peripheral substitution of the dipyrrinato ligand induces red-shifts in the absorption spectra and increases the oxidation potential of the bound iron. Steric interactions between the peripheral halogens and the 5-substituent of the dipyrrinato ligand can induce distortion of the ligand from planarity, resulting in widely varying 57Fe Mössbauer quadrupole splitting (|ΔEQ|) parameters. / Chemistry and Chemical Biology

Orientador: André Luiz Barboza Formiga / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-24T11:05:13Z (GMT). No. of bitstreams: 1 Santos_SabrinaGraciados_M.pdf: 7184130 bytes, checksum: a334f9344fec73d7b0af53f37a86c3f1 (MD5) Previous issue date: 2014 / Resumo: Foram sintetizados dois ligantes 5 fenildipirrometeno (2) e 5-(4-piridil)dipirrometeno (4) através da oxidação de seus respectivos intermediários (1) e (3). Um terceiro intermediário, bisdipirrometeno (5) foi sintetizado e oxidado resultando no ligante bisdipirrometeno (6) parcialmente oxidado. Essas moléculas foram caracterizadas através das técnicas de 1HRMN e MS. Realizou-se a síntese com complexo [CulL24]que foi caracterizado por FT-IR, espectroscopia no UV-Vis e MS. Comparando-se os dados de UV-Vis com os resultados de TD-DFT, um modelo de quatro orbitais moleculares de simetria "Pi" foi proposto para a interpretação dos espectros eletrônicos dos ligantes (2), (4), e (6) e do complexo, similar ao já existente para porfirinas. Também foram estudadas via modelagem molecular três supermoléculas distintas derivadas dos ligantes sintetizados, duas lineares e uma em forma de grade. As estruturas e distâncias entre os centros metálicos (entre 12,6 A e 20,2 A) foram então comparadas / Abstract: Abstract: In this work, three ligands and its intermediaries were synthesized and caracterized (5-phenildipyrromethene (2), 5-(4-pyridil)dipyrromethene (6) and bisdipyrromethene (4)), aiming a future complexation of each one of them with transition metals to form metallic complexes. The ligands (4), (6) and its intermediaries have two coordination sites in their structures, making them interesting for coordination polymers and metal organic frameworks synthesis. The intermediaries were synthesized and caracterized by hydrogen nuclear magnetic ressonance (1H NMR) and mass spectrometry (MS). The ligands (2), (4) and (6) were obtained through the oxidation of their respectives intermediaries, with (2) and (6) being known in the literature, while there are no reports of the ligand (4). The final products were caracterized also by 1H NMR and MS. With the ligand \pyreno \ caracterized, we performed the complexation of this ligand with copper, originating the complex [Cu(4-pyrdpm)2], caracterized by infrared spectroscopy (IR), UV-Vis spectroscopy and MS. All the analyses confirmed the complex. We studied the ligands, complexes and coordination polymers with Density Functional Theory / Mestrado / Quimica Inorganica / Mestra em Química

About 85% of the world’s energy is derived from non-renewable sources—coal, petroleum, and natural gas. Solar photocatalysis is one way to potentially generate renewable fuels. Zinc dipyrrin complexes have the potential to be efficient sensitizers for reductive photochemistry, but their ability to form long-lived triplet excited states needs further investigation. The overall aim of this research is to compare the photophysical properties zinc and boron dipyrrin complexes and investigate the role of the charge separated state in triplet state formation. This presentation will describe the synthesis and purification of zinc and boron dipyrrin complexes and their photophysical characterization, including fluorescence quantum yields in a series of solvents and their emission at low temperatures.

Photocatalytic carbon dioxide reduction transforms CO2 to useful chemicals and fuels, reducing CO2 emissions and making fossil fuels more renewable. Due to a lack of earthabundant sensitizers, we want to design new earth-abundant sensitizers to go with the many known carbon dioxide reduction catalysts. Zn(II) dipyrrin complexes strongly absorb visible light, but their excited state properties have not been widely studied. To investigate their photophysical properties, two Zn dipyrrin complexes, with and without heavy atoms, were synthesized and characterized by NMR and mass spectrometry. The photophysical properties of the two complexes were measured in polar and non-polar solvents, particularly fluorescence quantum yield and extinction coefficient. Also, through transient absorption spectroscopy, the triplet state quantum yield of both complexes was measures to determine the effect of solvent polarity and heavy atoms on the triplet state formation.

Metal complexes of dipyrromethene (dipyrrins) used as sensitizers in photocatalysis offer a way to harness solar energy in chemical bonds to create new fuels. This offers the dual role of reducing fossil fuel dependence and atmospheric CO2 levels. Traditionally, metal dipyrrin complexes are synthesized using substituted pyrroles, aldehydes, and transition metals. Indoles have a more expanded pi-electron system and their dipyrrin-type complex may exhibit visible light absorption, suggesting that they can act as photosensitizers for CO2 reduction processes. A novel indoledipyrromethene was synthesized using unsubstituted indole and mesitaldehyde. The complex exhibits visible light absorption at 422 nm. Its Zn coordinated complex it likely to exhibit blue-green light absorption making it suitable as a sensitizer for CO2 photoreduction and other applications.

Analogues structuraux des porphyrines et des Salens, des ligands de type dipyrrométhène bis-phénol ont été étudiés dans notre groupe, notamment sous forme de complexes pour la catalyse d'oxydation. L'activité catalytique de ces complexes étant faible, il a été proposé de remplacer les phénols par des triazoles. L'objet de cette thèse était d'étudier et de valoriser une nouvelle famille de ligands dipyrrométhène bis-triazole.Plusieurs voies de synthèse ont d'abord été étudiées et optimisées pour accéder à ces nouveaux ligands. Nous nous sommes attachés ensuite à valoriser ces nouveaux ligands selon plusieurs axes.Un de ces ligands a été testé en reconnaissance d'anions, ainsi que les dérivés monotriazolium et bis-triazolium. Les triazoliums ont également permis l'accès à des métallocomplexes carbéniques, qui ont été étudiés.Par ailleurs, les métallocomplexes des dipyrrométhène bis-triazole ont été préparés et caractérisés, y compris par électrochimie. Des essais d'utilisation en oxydation ont été entrepris. Enfin, la synthèse de BODIPYs® liposolubles et hydrosolubles a été réalisée. Les propriétés optiques ont été mesurées puis ces dérivés fluorescents ont été testés pour le marquage fluorescent de cellules HeLa / Known as structural analogues of porphyrins and Salens, dipyrromethene bis-phenol-type ligands have been studied in our group, especially as complexes for oxidation catalysis. Due to the poor catalytic activity of these complexes, it has been proposed to replace the phenol moieties with triazoles. The purpose of this thesis was to study and develop a new family of dipyrromethene bis-triazole ligands.Several synthetic routes were first investigated and optimized to reach these new ligands. We then have endeavoured to add value to these new ligands along several lines.The ligand has been tested in anion recognition, as well as monotriazolium and bis-triazolium derivatives. The triazoliums also allowed access to carbene metallocomplexes that were studied.Furthermore, dipyrromethene bis-triazole metallocomplexes were prepared and characterized, notably by electrochemistry. Oxidation catalysis tests were undertaken.Finally, the synthesis of liposoluble and hydrosoluble BODIPYs® was performed. Their optical properties were measured and these fluorescent derivatives were tested for the fluorescent labeling of HeLa cells

With increasing concerns of global warming and the impending exhaustion of fossil fuels attention is being turned to renewable sources of energy. The sun supplies 3 x 1024 J per year to the earth which is around 104 times more energy than what the human race consumes. The world’s energy needs would be satisfied if a mere 0.1% of the planet’s surface was covered with solar cells(< = 10%)1, causing the conversion of solar energy (sunlight) into electricity to represent a very practical renewable source. Past research into solar energy has produced a photovoltaic device, which when coupled with highly coloured coordination compounds, enables this conversion. This device is known as a dye-sensitised solar cell (DSSC). Further research has been conducted into the properties of the dyes, and has shown that highly coloured coordination compounds are able to convert solar energy into electrical energy with the highest efficiencies. The dominant compounds in this area to date have been Grätzel’s ruthenium complexes and porphyrins. However, there exists a class of smaller compounds called dipyrrins, described most simply as “half a porphyrin”, which possess many of the attractive qualities for DSSC dyes. Although there are no examples of ruthenium-dipyrrin complexes in the literature, the combination of advantageous properties from both components represent very attractive synthetic targets with huge potential as dyes for DSSCs. The objectives of this thesis were firstly to develop a series of dipyrrin complexes which would be suitable as dyes for DSSCs; then to fully characterise the complexes and investigate the spectroscopic properties of each complex; and finally to determine the suitability of the complexes as dyes for DSSCs. These objectives were fully met, resulting in a set of generic target compounds characterised via 1H NMR, 13C NMR, mass spectrometry (ESI-MS), elemental analysis, and x-ray crystallography. From analyses of the UV-visible, fluorescence, emission, and Raman spectra; and electrochemistry results; the complexes were concluded to be suitable as dyes for DSSC’s. An additional bonus is that the syntheses for these complexes are applicable to any dipyrrin, thus aiding future studies into the use of dipyrrins as dyes for DSSC’s. This thesis summarises the findings of the above outlined research project.

Bis(1,3,7,9-tetramethyl-5-mesityldipyrrinato)zinc(II) (ZnDPY) was synthesized in the lab by the McCusker group and a procedure was created to analyze its ability as a photosensitizer, a molecule that provides the energy for the reaction to occur by capturing light energy and turning it into a form that can be used by the photocatalyst. While more work is needed, preliminary steps have been made to create a process that can analyze the amount of carbon monoxide produced by a photocatalytic CO2 reduction reaction with ZnDPY as the photosensitizer. Progress has been made via the setup of a reaction apparatus, targeted gas chromatography (GC) peak separation, and GC calibration. More work will need to be done in order to determine the optimal reaction mix to showcase the sensitizer’s potential.

About 85% of the world’s energy is derived from non-renewable sources—coal, petroleum, and natural gas. Solar photocatalysis is one way to potentially generate cheap renewable fuels by harnessing energy from the sun using a photosensitizer and converting it into chemical energy. The efficiency of a photosensitizer depends on its capacity to form a prolonged triplet excited state. Zinc dipyrrin complexes have the potential to be efficient sensitizers for reductive photochemistry, but their ability to form long-lived triplet excited states still needs extensive research. The overall aim of this research is to probe the role charge separation plays in the formation of triplet state in metal complexes of dipyrrin photosensitizers. The specific objectives are to synthesize and characterize zinc and boron dipyrrin complexes, analyze their photophysical properties—such as steady state spectroscopy, low temperature emission spectroscopy—and quantify their triplet states using time-resolved transient absorption spectroscopy.

About 85% of the world’s energy is derived from non-renewable sources—coal, petroleum, and natural gas. Solar photocatalysis is one way to potentially generate cheap renewable fuels by harnessing energy from the sun and converting it into chemical energy. Photosensitizers serve as materials that absorb and store sunlight in the form of chemical energy. The efficiency of a photosensitizer depends on its capacity to form a prolonged triplet excited state. Zinc dipyrrin complexes have the potential to be efficient sensitizers for reductive photochemistry, but their ability to form long-lived triplet excited states still needs extensive research. The overall aim of this research is to probe the role charge separation plays in the formation of triplet state in metal complexes of dipyrrin photosensitizers. The specific objectives are to synthesize and characterize zinc and boron dipyrrin complexes, analyze their photophysical properties—such as steady-state spectroscopy, low-temperature emission spectroscopy—and quantify their triplet states using time-resolved transient absorption spectroscopy.