Comparação e validação de técnicas clássicas e modificadas para estudos de potencial genotóxico de peptídeos utilizados na produção de radiofármacos

Dissertação (Mestrado em Tecnologia Nuclear)

Nuevas aplicaciones sintéticas de pequeños heterocíclos. 2H-Azirinas fosforadas.

238 p.

Avaliação de heterociclo do tipo mesoiônico solubilizado em sistema microemulsionado para aplicação em dutos

The efficiency of inhibition to corrosion of steel AISI 1018 of surfactant coconut oil saponified (SCO) and heterocyclic type mesoionics (1,3,4-triazólio-2-tiolato) in systems microemulsionados (SCO-ME and SCO-ME-MI) Of type O/A (rich in water emulsion) region with the work of Winsor IV. The systems microemulsionados (SCO-ME and SCO-ME-MI) were evaluated with a corrosion inhibitor for use in saline 10,000 ppm of chloride enriched with carbon dioxide (CO2). The assessment of corrosion inhibitors were evaluated by the techniques of linear polarization resistance (LPR) and loss of weight (MW) in a cell instrumented given the gravity and electrochemical devices. The systems were shooting speed of less than 60 minutes and efficiency of inhibition [SCO-ME (91.25%) and SCO-ME-MI (98.54%)]

Síntese, estudos fotofísicos e imageamento celular de peptóides-cumarínicos fluorescentes baseados em Reações de Ugi

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Química, 2016.

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

In this review, we consider the main processes for the asymmetric transfer hydrogenation of ketones from 2008 up today. The most effective organometallic compounds (derived from Ru, Rh, Ir, Fe, Os, Ni, Co, and Re) and chiral ligands (derived from amino alcohols, diamines, sulfur- and phosphorus-containing compounds, as well as heterocyclic systems) will be shown paying special attention to functionalized substrates, tandem reactions, processes under non-conventional conditions, supported catalysts, dynamic kinetic resolutions, the use of water as a green solvent, theoretical and experimental studies on reaction mechanisms, enzymatic processes, and finally applications to the total synthesis of biologically active organic molecules.

Selective Sonogashira Couplings in 1,2,4,5-tetrazine derivatives

1,2,4,5-Tetrazines are six-membered heterocyclic compounds in which the four nitrogen atoms are displayed in a symmetric fashion. Their reactivity is quite different from other heterocyclic aromatic systems due to its unique electron-withdrawing character, comparable to tetra-nitrobenzene. 1 In particular, 1,2,4,5- tetrazines are known to take part in [4+2] inverse-Diels–Alder cycloaddition processes which efficiently lead to the construction of substituted pyridazine systems that are important in drug development and biomarker applications. 2 However, the electronic character of 1,2,4,5-tetrazines hampered the development of 3- ethynyl- and 3,6-diethynyl-1,2,4,5-tetrazine derivatives for molecular electronic applications, proved by the scarcity of examples found in the literature. 3 Herein, we describe the synthesis and characterization of two novel ethynyl-based 1,2,4,5-tetrazine derivatives. Synthesis of 3,6-(4-bromophenyl)-1,2,4,5-tetrazine precursor (1) was achieved in good yield by Pinner’s method, starting from 4-bromobenzonitrile. Despite its low solubility in common organic solvents, this precursor was found to react smoothly under typical Sonogashira coupling conditions to selectively afford the 3-ethynyl (2) and 3,6-diethynyl (3) protected derivatives (Figure 1). Reaction conditions were evaluated in order to provide the best yields and to promote selectivity of the mono- or disubstituted ethynyl derivatives. Finally, deprotection was achieved affording, in the case of compound 3, an unprecedented 3,6- diethynyl-1,2,4,5-tetrazine compound. Time-Dependent Density Functional Theory (TDDFT) calculations for both deprotected ethynyl derivatives were used to simulate electronic spectra. A deep knowledge of the relevant electronic transitions involved and quantitatively satisfactory results of the calculated electronic excitations in comparison with experimental data were obtained.

Homoleptic and Heteroleptic Metal Carbonyl Clusters and Nanoclusters

This Thesis aims at presenting the general results achieved during my PhD, that was focused on the study and characterisation of new homoleptic and heteroleptic metal carbonyl clusters. From a dimensional point of view, the nuclearity of such species ranges from 2 to 44 metal atoms. Lower nuclearity compounds may be viewed as polymetallic complexes, whereas higher nuclearity species can reach the nanocluster size, by resembling to ultrasmall nanoparticles (USNPs). Initially, my research was focused on the investigation of small MCCs stabilised by N-Heterocyclic carbene (NHCs) ligands. At this regard, a general strategy for the synthesis of mono-anionic [Fe(CO)4(MNHC)]− and neutral Fe(CO)4(MNHC)2, Co(CO)4(MNHC) (M = Cu, Ag, Au; NHC = IMes, IPr) species has been developed. Furthermore, during this investigation, neutral trimetallic Fe(CO)4(MNHC)(M’NHC) (M, M’ = Cu, Ag, Au; M ≠ M'; NHC = IPr) and neutral heteroleptic Fe(CO)4(MNHC)(MNHC’) (M = Au; NHC = IMes, IPr) compounds have been isolated. Thermal treatment turned out to be an efficient method for the growth of the dimension of MCCs. Indeed, species of the type [M3Fe3(CO)12]3– and [M4Fe4(CO)16]4– (M = Ag, Au) as well as larger clusters were formed during the thermal treatment of the new Fe-M (M = Ag, Cu, Au) carbonyl compounds. These species inspired the investigation of promising reaction paths for the synthesis of Fe-M (M = Ag, Cu, Au) carbonyl compounds devoid of ancillary ligands and alloy MCCs, such as the heterometallic [MxM’5-xFe4(CO)16]3− (M, M' = Cu, Ag, Au; M ≠ M'; x = 0-5) carbonyl clusters. The second part of this Thesis regards high nuclearity MCCs. In particular, new strategies for the growth of platinum carbonyl clusters involving, for instance, the employment of bidentate phosphines are described, as well as the syntheses and the thermal decomposition of new Ni-M (Pd, Pt) carbonyl clusters.

I) Improving low photocurrent of pseudorotaxane based solar cell II) Synthesis and characterization of new Fe(0) cyclopentadienone complexes

Next to conventional solar panels that harvest direct sunlight, p-type dye-sensitized solar cells (DSSCs) have been developed, which are able to harvest diffuse sunlight. Due to unwanted charge recombination events p-type DSSCs exhibit low power conversion efficiencies (PCEs). Previous research has shown that dye-redox mediator (RM) interactions can prevent these recombination events, resulting in higher PCEs. It is unknown how the nature of dye-RM interactions affects the PCEs of pseudorotaxane-based solar cells. In this research this correlation is investigated by comparing one macrocycle, the 3-NDI, in combination with the three dyes that contains a recognition sites. 2D-DOSY-NMR experiments have been conducted to evaluate the diffusion constants (LogD) of the three couple. The research project has been stopped due to the coronavirus pandemic. The continuation of this thesis would have been to synthesize a dye on the basis of the data obtained from the diffusion tests and attempt the construction of a solar cell to then evaluate its effectiveness. During my training period I synthetized new Fe(0) cyclopentadienone compounds bearing a N-Heterocyclic Carbene ligand. The aim of the thesis was to achieve water solubility by modifications of the cyclopentadienone ligand. These new complexes have been modified using a sulfonation reaction, replacing an hydroxyl with a sulfate group, on the alkyl backbone of the cyclopentadienone ligand. All the complexes were characterized with IR, ESI-MS and NMR spectroscopy, and a new Fe(0) cyclopentadienone complex, involved as an intermediate, was obtained as a single crystal and was characterized also with X-Ray spectroscopy.

Synthesis of manganese organometallic complexes

Il presente lavoro di tesi si inserisce in un progetto di ricerca volto alla sintesi di nuovi complessi di metalli di transizione per lo sviluppo di catalizzatori da impiegare in reazioni di catalisi omogenea. In particolare il mio progetto si è concentrato sulla sintesi di complessi organometallici di manganese con leganti carbenici N-eterociclici (NHC). La scelta dei leganti è stata effettuata in modo tale da poter avere leganti chelanti NHC di tipo MIC (mesoionic carbene) sintetizzati tramite cicloaddizione tra un alchino ed un azide catalizzata da rame (CuAAC) e N-alchilazione. Lo studio di questi complessi a base di manganese è ancora tutt’oggi agli albori, leganti NHC vengono molto utilizzati grazie alla possibilità di variarne le proprietà steriche ed elettroniche e alla possibilità di formare legami forti con quasi tutti i metalli. Il manganese è stato scelto poiché un elemento abbondante, poco tossico e poco costoso. The present thesis work is part of a research project aimed at the synthesis of new transition metal complexes to be used in homogeneous catalysis reactions. In particular my project focused on the synthesis of manganese organometallic complexes with N-heterocyclic carbene ligands (NHC). The choice of ligands was carried out to have NHC chelating ligands of the class of MIC (mesoionic carbene). These ligands are synthesized by cycloaddition between alkyl and azide with a copper-catalyzed reaction (CuAAC) and N-alkylation in order to obtain MIC after deprotonation. The study of these manganese-based complexes is still in its infancy today, NHC ligands are widely used thanks to the possibility of varying their steric and electronic properties and the possibility of forming strong bonds with almost all metals. The choice of manganese was made because is an abundant, low-toxic and inexpensive element.

Theoretical and experimental investigations on homologation of ethanol to butanol using a ruthenium-based catalyst

The mechanism of homologation of bioethanol to butanol and higher alcohols via the Guerbet reaction was computationally and experimentally investigated. The catalytic pathway involves a ruthenium-based complex and a base co-catalyst which work simultaneously. Due to selectivity issues, secondary products were formed and high competition between main pathway and side reactions was recorded. Herein, the overall catalytic mechanism for all the processes involved in was investigated, also considering the principal side reactions, using density functional theory (DFT) methods and experiments to confirm theoretical outcomes. Due to the complexity of the reaction network, kinetic simulations were established from DFT results, confirming experimental products distribution and giving insights into the factors governing the reaction mechanism.

Diazene photoswitches in artificial molecular machines and light-effected materials

The research developed in this thesis focused on the spectroscopic and photochemical characterization of molecular diazene photoswitches, both as individual species and as functional components of mechanically interlocked molecules, molecular-based materials and artificial molecular machines and motors. Among the plethora of photochromes reported so far, azobenzene is the most versatile photoswitch due to its reproducible and well-established photochemical properties. Part I of this thesis work focuses on the characterization of light-responsive supramolecular systems based on azobenzene: a photochemically-driven rotary motor, a light-responsive supramolecular polymeric material and a supramolecular system capable of photoinduced entantiodiscrimination. Despite the wide success of azobenzene photoswitches, the tunability of their photochemical properties as a function of the diversified substitution pattern on its aryl ring presents intrinsic limitations. To overcome this issue, in the last decade heteroaryl azoswitches (i.e., azobenzene having heterocyclic rings in place of one or both phenyl groups) have attracted a great deal of attention. Hence, Part II of this thesis work treats the photochemical characterization of two different families of azoheteroarenes embedding imidazolium and thienyl functionalities in their structures. Their potential implementation in water-soluble artificial molecular machines and light-effected semiconductor materials is also assessed.