Dipartimento di Chimica e Tecnologie Chimiche - Tesi di Dottorato

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Questa collezione raccoglie le Tesi di Dottorato afferenti al Dipartimento di Chimica e Tecnologie Chimiche dell'Università della Calabria.

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End date: 2022Subject: search.filters.subject.Chimica inorganica

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    Sintesi e caratterizzazione di materiali bioattivi e/o cromonici a base di complessi di metalli di transizione
    (2014-12-12) Sanz Mendiguchia, Barbara; Bartolino, Roberto; Crispini, Alessandra
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    Theoretical investigation of the enzyme promiscuity within the carbonic anhydrase's family
    (2014-11-28) Piazzetta, Paolo; Bartolino, Roberto; Marino, Paolo
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    A DFT and TDDFT study of molecules with interest on photodynamic theraphy
    (2012) Fortes Ramos, Flavio Sousa; Russo, Nino; Bartolino, Roberto
    This PhD work concerns the theoretical photochemistry study of molecules with an interest on Photodynamic Therapy (PDT). PDT is a medical technique for the treatment of different tumor diseases, such as age related macular degeneration, psoriasis or bladder cancer. This technique is increasingly being required, in particular in cases when conventional methods, chemotherapy and radio therapy fail to be successful. It consists of the administration of photosensitizer (a drug) followed by light irradiation and requires the presence of molecular oxygen on tissue to be destructed. On molecular terms the action of the drug is explained by the excitation of the drug to a singlet state after light irradiation, followed by its conversion of to a triplet state. This triplet state, in more common cases, directly transfers its energy to molecular oxygen producing singlet oxygen. In other cases the photophysical parameters of the triplet state are such that it is allowed to participate in electron transfer reactions, where it becomes reduced and after its anion reduces oxygen forming radical oxygen species, that like singlet oxygen, is toxic to the cell, resulting in cellular death by apoptosis or necrosis. As chemists, our main interest is on the proposal of drugs with ideal photophysical and solution properties. In regards to the first aspect, a drug should have an intense absorption on the red part of the visible spectra, known as therapeutic window, where the body tissue has a better penetration. Furthermore, the drug should have ideal photochemistry parameters to participate in the reaction. For the activation of oxygen it should have a triplet energy higher than the 0.98 eV of oxygen triplet and for others photochemical mechanism of action it should have the ideal parameters namely, ionization potentials and electron affinities. The drug should be soluble in water to react on the cells, that is usually provided by an hydrophilic chemical group incorporated on the drug. In order to have fewer side effects and a decreased drug dose, the drug should preferentially be localized on the tumor site. In reality, the question to find an ideal drug goes beyond chemistry crossing the fields of physics and clinical medicine. It involves physical problems like the interaction of light and body tissue with better dispositive or lasers for light irradiation to be developed. On the clinical part, it is evaluated on the in vitro or in vivo toxicity of the drug as well as the drug’s side effects. The organic and inorganic chemists are interested on the synthesis and characterization of the new drugs. The developments of new quantum mechanics methods with a good balance between accuracy and computational cost, namely Density Functional Theory (DFT) allowed the theoretical chemists to contribute to diverse fields like bio-medicine and other fields where the size of the systems can have dimensions large enough to be studied by older quantum mechanics methods. On the particular question of PDT, the simulation of electronic spectrum and calculation of photochemical parameters can be a support to the work of experimentalist on his synthesis strategy and on the interpretation of obtained data. The chemist experimental work on PDT, usually starts with a tetrapyrrolic macrocycle, natural like porphyrin or synthetic like phthalocyanine. Its structure is modified by the incorporation of substituent groups (e.g phenyl groups) that extends the electron conjugation that can shift the maximum absorption wavelength, λmax, to red part. The possibility of predicting the effect of a substituent group can address the synthesis to a molecule than another. Also, the calculation of the photochemical parameters of the drug allows the evaluation of the feasibility of a mechanism. For example, the electronic energy of the first triplet state furnishes a first estimation on the capability of a drug to generate singlet oxygen. The theoretical methodology in this work is Density Functional Theory (DFT) for the optimization of the structures and its time dependent formalism (TDDFT) for the calculation of electronic excitations. The behavior in solutions is simulated by the solvent implicit methods(C-PCM). On the first part of the study, we focus on two compounds designed to be used on PDT, belonging to the class pentaporphyrins that are porphyrin like molecules containing five pyrrole rings. These compounds were subject to clinical studies were they have shown a PDT action. We predict the electronic spectra and further investigate the mechanism of action of these compounds. On a second part of the study, we focus on corroles - molecules analogues to porphyrin - and its metal complexes, which synthesis were recently reported. We investigate the electronic spectra and evaluate the ability to produce singlet oxygen. The third part of the study consists on a non porphyrin based compounds – the squarines. These molecules are much known to their use in photo cells devices. Their sharp transitions make them as promising drugs to be used on PDT.
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    Bio-medicinal applications of coordination compounds: a photophysical point of view
    (2012-11-26) Ricciardi, Loredana; Russo, Nino; La Deda, Massimo; Bartolino, Roberto
    Il presente lavoro di ricerca, svolto presso il Laboratorio di Chimica Inorganica e di Coordinazione (LaCIC) dell'Università della Calabria, sotto la supervisione del Dott. Massimo La Deda, e in parte nel Laboratoire de Physico-Chimie des Matériaux Luminescents (Université Claude Bernard, Lyon, France), si colloca all'interfaccia tra la Biomedicina, la Chimica di Coordinazione e la Fotochimica, alla ricerca di un comune denominatore. L'obiettivo del nostro lavoro è stato quello di sviluppare una metodologia ed un set-up sperimentale per collegare l'esperienza del LaCIC nella sintesi organometallica, con le applicazioni di composti di coordinazione in campo biomedico. Abbiamo scelto tre aree di ricerca in grado di mettere in evidenza la relazione tra "composti di coordinazione", "luce" e "biomedicina": l'applicazione di complessi metallici incapsulati in polimeri o in nanoparticelle di oro e silice per la generazione di ossigeno di singoletto nella Terapia Fotodinamica (Capitoli 3 e 4), l'utilizzo dei processi a trasferimento di energia che coinvolgono i composti di coordinazione per lo studio delle interazioni farmaco-proteina (applicazioni di “sensing”, capitolo 2), l'utilizzo della luminescenza di nanoparticelle contenenti complessi di metalli di transizione nell’imaging cellulare. Le proprietà uniche dei composti metallici, soprattutto la rilevante fotochimica e fotofisica dei composti di metalli di transizione, li rendono idonei per applicazioni in fotomedicina. Capitolo 2 - Applicazione di “sensing” dei composti di coordinazione: interazione farmaco-proteina. Un nuovo complesso di zinco, recentemente sintetizzato presso il LaCIC, ha evidenziato un’interessante attività antiproliferativa in vitro nei confronti di alcune linee cellulari tumorali. Tuttavia, i test in vitro rappresentano solo il primo step per l’applicazione di questo complesso come farmaco antineoplastico; una fase successiva richiede uno studio della sua biodistribuzione, dunque la sua interazione con biomolecole quali l’ Albumina sierica umana, la proteina più abbondante presente nel torrente circolatorio, la quale aumenta la solubilità di farmaci idrofobici nel plasma e ne modula il rilascio a livello cellulare. Grazie alla fluorescenza della proteina, è stato possibile studiarne il fenomeno di quenching della luminescenza, correlandolo all’interazione di legame con il complesso metallico. Inoltre, la "struttura speciale" del composto di coordinazione, la sua luminescenza intrinseca, ha reso possibile lo studio dell’interazione di legame da un’altra prospettiva, giungendo ad una interessante conclusione, che evidenzia l'aspetto multifattoriale del complesso: terapeutico e sensoristico. Capitolo 3 - Processi attivati dalla luce in composti di coordinazione: fotogenerazione di ossigeno di singoletto. La Terapia Fotodinamica (PDT) fa riferimento all’applicazione di luce al fine di ottenere un effetto terapeutico, in particolare fa riferimento alla capacità di fotogenerare 1O2, una specie altamente reattiva (il “vero” agente terapeutico) da una molecola cosiddetta “fotosensibilizzante”. Tra gli effetti terapeutici dell’ 1O2 si pongono in evidenza la terapia antimicrobica e, soprattutto, la terapia antitumorale: in entrambe è preferibilmente richiesto l’utilizzo di fotosensibilizzanti solubili in acqua. I Complessi di Metalli di Transizione (TMC), grazie alle loro “speciali” proprietà fotofisiche, sono fotosensibilizzanti eccellenti, ma per la maggior parte scarsamente idrofilici. Per rendere TMC solubili in acqua si può procedere per esempio inserendoli in un polimero biocompatibile, senza che gli stessi perdino la loro capacità di generare ossigeno di singoletto. Seguendo questo criterio, è stato sintetizzato e caratterizzato il primo esempio di un polimero solubile in acqua legante un complesso di Pt(II) in grado di generare ossigeno di singoletto. Capitolo 4 - Il paradigma “theranostic”: complessi di metalli di transizione e nanoparticelle. Un’altra alternativa per ottenere un fotosensibilizzante solubile in acqua con le “speciali” proprietà dei TMC è di incapsularlo all’interno di nanoparticelle (NPs), le quali stanno sempre più acquisendo una crescente importanza in ambito medico, grazie alla capacità di agire da sistema di rilascio e alla loro bassa tossicità. Su questa base, sono state sintetizzate e caratterizzate un certo numero di NPs aventi un “core” d’oro e una “shell” di silice con intrappolati nella matrice complessi di Ir (III) e Ru (II), aventi la capacità di generare ossigeno di singoletto. Come prova preliminare, un campione di NPs contenenti un complesso di Ru (II), è stato caratterizzato in vitro per valutarne la citotossicità in diverse linee di cellule tumorali, con risultati promettenti. Inoltre, le "speciali" proprietà fotofisiche dei TMC consentono una disattivazione non radiativa degli stati eccitati (fenomeno necessario per la generazione di 1O2 mediante un processo a trasferimento di energia) senza perdere la luminescenza. In virtù di questo, è stato possibile localizzare le NPs fotosensibilizzanti all'interno della cellula mediante microscopia a fluorescenza, rendendo le NPs sintetizzate un nuovo materiale per “theranostic purposes”.
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    Hydrophilic Ir(III) complexes suitable for the construction of functional mesoporous materials
    (2012-11-27) Yadav, Yogesh Jivajirao; Versace, Carlo; Ghedini, Mauro; Bartolino, Roberto
    Nowadays, intensive efforts have been carried out on the design of novel advanced molecular materials, which can self-assemble in a strong, directional and reversible way to construct supramolecular materials with specific properties. The rational design and preparation of supramolecular assemblies through the coordination of metal ions with organic ligands has attracted attention for developing novel crystalline materials with interesting structural topologies and promising applications, and has evolved as an interesting research. The metals used in these complexes can serve as structural components and/or as a source of properties (e.g., magnetic, catalytic, optoelectronic, etc). Cyclometallated Ir(III) octahedral complexes possess fascinating properties used in various applications such as luminescent and electrochemiluminescent labeling reagents for biological substrates1, sensors2, or electronic devices3,4. Recently, the interest in ionic Ir(III) complexes is growing rapidly because not only high internal quantum efficiency (~100%) can be achieved in principle, but also tunable emission wavelengths over the entire visible spectrum can be successfully obtained through ingenious modification of ligands. In particular, Ir(III) complexes based on the chelating ligand 2,2’-bipyridine (bpy) have been successfully applied in light-emitting electrochemical cells (LECs) and sensors.5 The theoretically calculated phosphorescence yield (Fp) of the Ir(III) complexes are close to unity in solution.6 The solution investigations have made great contributions to the fundamental understanding of luminescence processes at molecular level. The conclusions drawn from the dilute solution data, however, cannot commonly be extended to the concentrated solutions. Indeed, many Ir(III) complexes show very different light-emitting behaviors in dilute and concentrated solutions and respectively in the solid state. The luminescence is often weakened or quenched at high concentrations, a phenomenon widely known as “concentration quenching”. A main cause for the quenching process is mechanistically associated with the “formation of aggregates”, which is probably why the concentration quenching effect has frequently been referred to as “aggregationcaused quenching” (ACQ). On the other hand “aggregation-induced phosphorescent emission” (AIPE) is an unusual phenomenon existing also in transition metal complexes, which have no emission in solution but enhanced emission in the solid state.7 There are some examples of AIPE, most of them in neutral Ir(III) complexes.8, 9, 10, 11, 12 The main strategies to avoid unpleasant quenching phenomena are based on the dispersion of the chromophore. Mainly, two strategies are employed: engineering at molecular level by introducing functionalities able to electronically disconnect the chromophores (bulky groups or functionalities capable to construct hard crystalline or soft dynamic supramolecular assemblies) or isolating the active molecules in different host matrices (host-guest systems).13 In particular, the dispersion of a chromophore into mesoporous materials not only prevents the aggregation phenomena but also provides increased thermal, chemical and mechanical stability to the final materials. Mesoporous materials are ordered porous materials with periodic distribution of pores, high surface area, controllable large pore sizes in the range of 2 – 50 nm and variable topology of the pores. The inorganic matrixes may be made up of SiO2, TIO2, ZrO2, Al2O3, Nb2O5 etc. Basically, the synthesis of ordered functional mesoporous materials is based on the condensation of an inorganic scaffold on the organised structure formed in water by surfactant molecules. Two different strategies may be employed, the cooperative self-assembly mechanism (CSA) and the true liquid crystal templating’ (TLCT) mechanism.14 The functionalization of the mesoporous material may be done in both cases by inserting the chromophore into the primarily water solution. Therefore, water soluble chromophores may guarantee a better compatibility with the surfactant/water system, whereas a proper functionalization on the molecular structure of the chromophore that permit the self-assembly into supramolecular ordered water assemblies, will allow to use the chromophores directly as structure directing agents (SDAs). Since the photophysical properties of the ionic complexes are influenced profoundly by the surroundings of the molecule both in solution and in condensed states, it is fundamental to study the behavior of such complexes in these different states, in order to achieve a fine tuning of the properties as a function of their structure and order in the final material. The knowledge gained in the assembling of supramolecular materials using non-covalent bonds may be used for the construction of ordered systems in water. This strategy will permit the one-step synthesis of functional mesoporous materials, and to control the order of the final material controlling the order in water of the functional Ir(III) complexes. In particular, the molecular fragments that one can change to achieve the desired properties in the final ionic Ir(III) complexes are the cyclometallating or coordinating ligands, and respectively the counterion. My research therefore is focused on the design and synthesis of hydrophilic ionic Ir(III) complexes with flexible or rigid ancillary ligands and use of different counterions, all suitable for controlling the supramolecular assembly in the solid state, and to transfer the knowledge gained into obtaining ordered structures in water, or water-surfactant systems, necessary for the synthesis of mesoporous materials with defined properties. The ionic octahedral Ir(III) complexes synthesised during this thesis and their classification in different classes are presented in the figure S1
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    Sintesi e caratterizzazione di complessi di Zn(II): un nuovo approccio per ottenere biomateriali
    (2011-09-27) Pirillo, Sante; Russo, Nino; Pucci, Daniela
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    Studio Teorico dei Dettagli Meccanicistici di Reazioni Organiche Catalizzate da Oro
    (2014-03-31) Mazzone, Gloria; Russo, Nino; Sicilia, Emilia
    The catalytic chemistry of gold has had a relatively belated development with respect to other late transition metals, and this has been attributed to the preconception that gold is expensive and unreactive. The interest in gold has grown over the last thirty years, because both of these conceptions have been proven false, and successful applications of gold catalysis have emerged in chemical processing, pollution control, fuel cells design, and many others fields. These evidences have sparked a veritable “gold rush” in the field of catalysis, both homogeneous and heterogeneous. We investigated the role of gold in both homogeneous and heterogeneous catalytic processes. In fact, the theoretical study of mechanistic details for reactions, that involves and underline the characteristics of gold, have been the subjects of this thesis. Density functional theory (DFT) is the method of choice in this kind of studies. Regarding heterogeneous catalysis the synthesis of vinylacetate is the reaction on which we have focused our attention. In particular, a bimetallic catalyst containing low Pd coverage on Au surface (100 and 111) has been selected to outline the reaction mechanism of VAM formation. We have studied in detail both mechanisms proposed in literature, in order to selected the more active surface and the more likely mechanism. The homogeneous catalytic process that has been selected to point out the catalytic activity of gold is the hydration of 1,2-diphenylacetylene to yield benzyl phenyl ketone, catalyzed by a complex of Au(I) with triphenylposphine. This cationic complex coordinates to the alkyne in the first step of the catalytic cycle, thus rendering it more susceptible for a nucleophilic attack. That reaction is a relatively new synthetic strategy that have recently studied experimentally. Our aim is to elucidate the mechanism of the whole reaction.
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