Synthesis and applications of porphyrinoids: a journey into the multifaceted chemistry of pyrrolic macrocycles

Nella vasta famiglia dei macrocicli polipirrolici, le porfirine ed i corroli rivestono un ruolo di primo piano, grazie al fatto che, nel corso degli ultimi decenni, sono state messe a punto molte strategie sintetiche volte ad ampliare la gamma delle possibili molecole target. Un altro elemento degno di nota è la loro versatilità, che ne ha permesso un ampio utilizzo in differenti campi di applicazione. Lo studio della reattività di questi composti, ed il loro possibile impiego in diversi campi di applicazione, sono stati gli obiettivi di questo lavoro di tesi. Il capitolo 1 è centrato sull’impiego delle porfirine come materiale sensibile per i sensori chimici. In particolare si è studiata la morfologia di film monomolecolari depositati su oro, ottenuti mediante legame covalente tra la superficie del metallo ed una porfirina opportunamente funzionalizzata (SAM - Self Assembled Monolayer). L’esatta morfologia del film organico è stata studiata mediante l’impiego di numerose tecniche spettroscopiche. Un'altra linea di ricerca ha riguardato la formazione, la caratterizzazione e l’utilizzo di aggregati supramolecolare di porfirine. E’ stato notato che, in determinate condizione, porfirine funzionalizzate con gruppi carichi tendono a formare aggregati aventi struttura ben definita. L’interazione dell’aggregato con ioni in soluzione o con VOCs (Volatile Organic Compounds) in fase gassosa, porta ad un’alterazione della sua geometria e quindi ad una variazione delle caratteristiche spettrali, molto più intensa rispetto a quanto sia possibile osservare con le singole unità costituenti l’aggregato stesso. Alla luce delle proprietà illustrate, questo materiale è stato impiegato come strato sensibile per l’analisi di VOCs mediante l’impiego della tecnica CSPT. Il capitolo 2 è centrato sullo studio della reattività dei corroli. I corroli sono tetrapirroli, che condividono con le porfirine la facilità di sintesi, a differenza di molti altri porfirinoidi che sono invece ottenibili soltanto attraverso lunghe e difficoltose procedure sintetiche. Si è così pensato di usare il corrolo come materiale di partenza per ottenere un altro macrociclo tetrapirrolico, l’isocorrolo, attraverso l’ottimizzazione di una strategia sintetica one-step. Finora non è stata mai messa a punto una procedura generalizzata per la demetallazione dei metallo corroli; infatti i complessi dei corroli sono spesso degli intermedi inevitabili per il raggiungimento di composti differentemente funzionalizzati. La ricerca di una procedura di demetallazione non troppo aggressiva nei confronti dei substrati, può infatti aprire la strada ad una più ampia gamma di funzionalizzazione di questo inusuale macrociclo. Nel capitolo 3, sono state gettate le basi per l’ottenimento di una metodologia di sintesi dei triaril-tetrabenzocorroli. I tetrabenzocorroli sono considerati corroli espansi. L’espansione dell’aromaticità di questi composti, così come si osserva nel caso delle tetrabenzoporfirine, causa uno spostamento verso il rosso delle bande di assorbimento e di emissione; questa proprietà è interessante poiché è una caratteristica chiave per lo sviluppo di fotosensibilizzatori per l’impiego nella PDT (Photo Dynamic Therapy), una tecnica non invasiva e non tossica per il trattamento di tumori e di altre malattie.Among the large plethora of polypyrrolic macrocycles, porphyrins and corroles hold a noteworthy role; indeed, in the last three decades, several synthetic strategies have been pursued, expanding in this way the library of available compounds, and consequently, the studies concerning their chemistry. Moreover, it is impossible to neglect the versatility of these macrocycles, which encouraged their exploitation in several field of research. The aim of this thesis concerns the reactivity of porphyrins and corrole derivatives, and the exploitation of such molecules in different field of application. Chapter 1 deals with the exploitation of porphyrin derivatives as sensitive material for chemical sensors. In detail, we studied the morphology of self assembled porphyrin monolayer (SAM), by covalently linking of suitable functionalised macrocycles onto the gold surface. This was accomplished by means of several spectroscopic techniques. The formation, the characterization and the exploitation of porphyrins-based supramolecular aggregates, has been also taken into consideration. It is known that, under particular conditions, charged porphyrin derivatives strongly self-interact, forming supramolecular structures with a well defined tubular like shape. These porphyrin nanotubes are able to interact either with cations in solution, or with VOCs (Volatile Organic Compounds) in gas phase. As a consequence of these interactions, the geometry of the assembly changes, resulting in a change of the nanotube spectral and optical features. These changes are larger in magnitude, compared to those featured by the separated components. The use of this system as organic sensitive material, has been carried out by CSPT system (Computer Screen Photoassisted Technique). Chapter 2 is focused on corroles reactivity. Differently from porphyrins and corroles, others porphyrinoids are achievable only by difficult and tedious synthetic procedures. We surmised that the use common triarylcorroles as starting material, could be a successful strategy to obtain different tetrapyrrolic macrocycles, namely isocorrole, in a single step-synthesis. In this chapter the refinement procedure for demetalation of corroles complexes is also described. The achievement of the free-base corrole, by demetalation procedure, has been so far a very hard task; indeed metallo-corroles are too often unavoidable intermediates of choice for the achievement of differently functionalised derivatives. The quest of a “substrate friendly” demetalation procedure, may open the way to a wide range of functionalizations of this unusual macrocycle. In Chapter 3, the basis for an efficient methodology of triaryl-tetrabenzocorroles synthesis, have been described. Tetrabenzocorroles are regarded as expanded corroles. The expansion of the aromaticity of these molecules, such as occurs for by analogy with the tetrabenzoporphryin case, leads to a red shift of their absorption and emission bands; this should be a very interesting property, as it is the key feature for the development of photosensitizers amenable of use in PDT (Photo Dynamic Therapy), a non invasive and low-toxicity technique for the treatment of tumours and others diseases

Experimental Realization of Polarization Qutrits from Non-Maximally Entangled States

Based on a recent proposal [Phys. Rev. A 71, 062337 (2005)], we have experimentally realized two photon polarization qutrits by using non-maximally entangled states and linear optical transformations. By this technique high fidelity mutually unbiased qutrits are generated at a high brilliance level.Comment: RevTex, 8 pages, 6 figure

Cloning Entangled Qubits to Scales One Can See

By amplifying photonic qubits it is possible to produce states that contain enough photons to be seen with a human eye, potentially bringing quantum effects to macroscopic scales [1]. In this paper we theoretically study quantum states obtained by amplifying one side of an entangled photon pair with different types of optical cloning machines for photonic qubits. We propose a detection scheme that involves lossy threshold detectors (such as human eye) on the amplified side and conventional photon detectors on the other side. We show that correlations obtained with such coarse-grained measurements prove the entanglement of the initial photon pair and do not prove the entanglement of the amplified state. We emphasize the importance of the detection loophole in Bell violation experiments by giving a simple preparation technique for separable states that violate a Bell inequality without closing this loophole. Finally we analyze the genuine entanglement of the amplified states and its robustness to losses before, during and after amplification.Comment: 15 pages, 9 figure

Quantum Cloning for Absolute Radiometry

In the quantum regime information can be copied with only a finite fidelity. This fidelity gradually increases to 1 as the system becomes classical. In this article we show how this fact can be used to directly measure the amount of radiated power. We demonstrate how these principles could be used to build a practical primary standard

Realization and characterization of a 2-photon 4-qubit linear cluster state

We report on the experimental realization of a 4-qubit linear cluster state via two photons entangled both in polarization and linear momentum. This state was investigated by performing tomographic measurements and by evaluating an entanglement witness. By use of this state we carried out a novel nonlocality proof, the so-called ``stronger two observer all versus nothing'' test of quantum nonlocality.Comment: 4 pages, 4 figure

Oral health profile of education and health professionals attending handicapped children

O objetivo deste estudo foi avaliar conhecimentos e atitudes em saúde bucal dos profissionais de educação e saúde, que atuam em um programa de atenção à criança de 0 a 6 anos de idade, portadora de necessidades especiais, em uma instituição municipal pública do Rio de Janeiro. Por meio de um formulário, foram entrevistados 67 profissionais (professoras, atendentes e profissionais de saúde). Os resultados foram comparados aos hábitos de higiene bucal das crianças, através da observação direta da rotina da creche. Embora 97,0% tenham afirmado que a saúde bucal pode interferir na saúde geral, somente 37,3% dos profissionais responderam corretamente a respeito dessa interferência. Quanto aos métodos de prevenção da cárie, 92,5% afirmaram conhecê-los, contudo somente 17,9% foram ao dentista para prevenção. A maioria (81,3%) indicou a higiene bucal como o modo de prevenir a cárie, porém a observação mostrou que nem sempre esta prática é realizada na creche. Quanto à época do início da escovação dos dentes das crianças, 75,0% das professoras e 94,4% dos profissionais de saúde afirmaram conhecer a necessidade de iniciar a escovação antes de um ano de vida, sendo essa resposta observada em somente 52,5% das atendentes (qui-quadrado, p = 0,006). Diante desses resultados, pôde-se concluir que as atitudes em saúde bucal nem sempre foram coerentes com os conhecimentos expressados por esses profissionais.The purpose of this study was to evaluate the knowledge and attitudes toward oral health of education and health professionals working in a children care program for handicapped children from 0 to 6 years of age, run by a public municipal institution in Rio de Janeiro. Using a printed questionnaire, 67 professionals (teachers, attendants and health professionals) were interviewed. The results were compared to the children's oral hygiene habits, by directly observing their daily nursery routine. Although 97.0% said that oral health could play a part in general health, only 37.3% of the professionals answered correctly on this matter. As for methods for preventing caries, although 92.5% said that they were aware of them, only 17.9% went to the dentist for preventive treatment. Although the majority (81.3%) indicated oral hygiene as a way of preventing caries, observation showed that this practice is not always put into effect in the program's day nursery. Regarding when to start toothbrushing in children, 75.0% of the teachers and 94.4% of the health professionals said that they were aware of the need to begin brushing before one year of age, although this reply was given by only 52.5% of the attendants (chi-square, p = 0.006). In view of these results, it was concluded that attitudes toward oral health were not always coherent with the knowledge that these professionals express

One-way quantum computation via manipulation of polarization and momentum qubits in two-photon cluster states

Four-qubit cluster states of two photons entangled in polarization and linear momentum have been used to realize a complete set of single qubit rotations and the C-NOT gate for equatorial qubits with high values of fidelity. By the computational equivalence of the two degrees of freedom our result demonstrate the suitability of two photon cluster states for rapid and efficient one-way quantum computing.Comment: RevTex4, 4 pages, 3 figure

Digital speckle pattern interferometry applied to a surface roughness study

Surface roughness determination is of great interest for many applications. Several methods can be found in the literature, but most of them rely on indirect evaluation of the information, such a s photographic techniques. We propose a method to measure surface roughness that takes advantage of digital speckle pattern interferometry for obtaining the data, and of digital image processing for evaluating it. After defining the problem, a theoretical description is presented, and finally it is compared with experimental results, showing good agreement