Photoredox catalysis for environmental and chemical applications. A mechanistically-based approach

En las últimas décadas, los procesos redox fotoinducidos mediados por luz visible han recibido gran atención debido a las suaves condiciones de operación en que se llevan a cabo. Como resultado, se han logrado posicionar como una alternativa más dentro de los Procesos de Oxidación Avanzada. Además, se han convertido en una metodología excepcional en síntesis orgánica, que ha abierto la puerta a nuevas rutas químicas con aplicaciones sintéticas. Sin embargo, a pesar del crecimiento del campo, se ha prestado poca atención a los mecanismos por los que operan estos procesos. El principal objetivo de esta tesis fue avanzar en la comprensión de distintos procesos fotoredox llevados a cabo empleando fotocatalizadores orgánicos. Más específicamente, se estudió la viabilidad de distintos fotocatalizadores orgánicos, y además, se realizó un estudio mecanístico detallado basado en técnicas resueltas en el tiempo. A partir de estos resultados, se estableció una metodología para determinar los puntos clave a considerar en un sistema fotoredox. En primer lugar, en la Parte I, se eligieron dos fotocatalizadores basados en sales de pirilio y tiapirilio, que operan mediante transferencia electrónica oxidativa, con distintos objetivos. En el Capítulo 3, se evaluó su aplicabilidad en la fotodegradación de dos contaminantes de la industria del corcho y se estudió el mecanismo por el que se produce dicha fotodegradación. En el Capítulo 4, se demostró la utilidad de la detección directa de todos los intermedios de vida corta derivados del TPP+ implicados en la oxidación fotocatalizada como herramienta para evaluar el nivel de fotodegradación. En el Capítulo 5, se empleó TPTP+ para establecer las mejores características de un fotocatalizador y la influencia de la concentración de las sustancias a oxidar en la eficiencia de los estados excitados, o en general, de los intermedios clave de vida corta. En segundo lugar, en la Parte II, en el Capítulo 6, se evaluó el potencial del Rosa Bengala en la eliminación de dos fármacos. Éste es un fotocatalizador típico en la remediación de aguas residuales conocido por actuar via mecanismo Tipo II. Se incluyó además un segundo fotocatalizador, Perinaftenona, cuyo rendimiento cuántico de oxígeno singlete es incluso mayor a Rosa Bengala. En el Capítulo 7, se llevó a cabo la fotooxidación de tres contaminantes, usando NMQ+, un fotocatalizador inusual, capaz de generar oxígeno singlete desde su estado excitado singlete. En todos los casos se pudo demostrar la mayor contribución del mecanismo Tipo I sobre el mecanismo Tipo II en la fotodegradación de los diferentes contaminantes. Finalmente, en la Parte II, el Capítulo 8 se dedicó a la reducción fotocatalítica de bromuros orgánicos, empleando Riboflavina, un colorante orgánico no metálico, como fotocatalizador. De nuevo, se prestó especial atención a la detección y comportamiento de las especies intermedias, lo que resultó de acuerdo a los datos termodinámicos.En les últimes dècades, els processos redox fotoinduïts mitjan per llum visible han rebut gran atenció degut a les suaus condicions d'operació en que es donen. Com a resultat, s'han aconseguit col·locar com una alternativa mes dins dels Processos d'Oxidació Avançada. A més, han estat convertint-se en una metodologia excepcional en síntesi orgànica, que ha obert la porta a noves rutes químiques amb aplicacions sintètiques. No obstant això, a pesar del creixement del camp, s'ha prestat poca atenció als mecanismes pels que operen aquests processos. El principal objectiu d'esta tesi va ser avançar en la comprensió de diferents processos fotoredox duts a terme emprant fotocatalitzadors orgànics. Més específicament, es va estudiar la viabilitat de distints fotocatalitzadors orgànics, i a més, es va realitzar un estudi mecanístic al detall basat en tècniques resoltes en el temps. Amb aquests resultats, es va establir una metodologia per a determinar els punts clau a considerar en un sistema fotoredox. En primer lloc, en la Part I, es van elegir dos fotocatalitzadors basats en sals de pirili i tiapirili, els quals operen per mitjà de transferència electrònica oxidativa, amb distints objectius. En el Capítol 3, es va avaluar la seua aplicabilitat en la fotodegradació de dos contaminants de la indústria del suro i es va estudiar el mecanisme pel qual es produeix dita fotodegradació. En el Capítol 4, es va demostrar la utilitat de la detecció directa de tots els intermedis de curt temps de vida derivats del TPP+ implicats en l'oxidació fotocatalitzada com a ferramenta per avaluar el nivell de fotodegradació. En el Capítol 5, es va emprar TPTP+ per a establir les millors característiques d'un fotocatalitzador i l'influencia de la concentració de les substàncies a oxidar en la eficiència dels estats oxidats, o en general, del intermedis claus de vida curta. En segon lloc, en la Part II, en el Capítol 6, es va avaluar el potencial del Rosa Bengala en l'eliminació de dos fàrmacs. Aquest es un fotocatalitzador típic en la remediació d'aigües residuals conegut per actuar via mecanisme Tipus II. Es va incloure a més un segon fotocatalitzador, Perinaftenona, el del qual rendiment quàntic d'oxigen singlet és inclús major a Rosa Bengala. En el Capítol 7, es va dur a terme la fotooxidació de tres contaminants, usant NMQ+, un fotocatalitzador inusual, capaç de generar oxigen singlet des del seu estat excitat singlet. En tots els casos es va poder demostrar la major contribució del mecanisme Tipus I sobre el mecanisme Tipo II en la fotodegradació dels diferents contaminants. Finalment, en la Part II, el Capítol 8 es va dedicar a la reducció fotocatalítica de bromurs orgànics, emprant Riboflavina, un colorant orgànic no metàl·lic, com fotocatalitzador. De nou, es va prestar especial atenció a la detecció i comportament de les espècies intermèdies, el que va resultar d'acord amb les dades termodinàmiques.In the last decades, photoinduced-redox processes mediated through visible light have obtained great attention due to the generally mild operating conditions that they offer. As a result, they constitute a further alternative within the so-called Advanced Oxidation processes. Besides, they are becoming an outstanding methodology in organic synthesis, which has opened the door to new synthetic and chemical routes. However, despite the growth of the field, little attention has been paid to the mechanisms pathways behind these processes. The main objective of this thesis was to gain deeper understanding of different photoredox processes carried out using organic photocatalysts. More specifically, the viability of several organic photocatalysts was studied, and besides, a careful mechanistic study based on time resolved techniques supported the postulated mechanisms. With this information, a methodology determining the key points to consider in a photoredox system were stablished. Firstly, in Part I, two photocatalysts based on pyrilium and thiapyrilium salts, which operate through an oxidative electron transfer, have been used with different objectives. In Chapter 3, the viability of the photodegradation of two common pollutants from cork industry and the mechanism behind it has been evaluated. In Chapter 4, the direct detection of all the TPP+ derived short-lived intermediates in the photocatalyzed oxidation of a mixture of pollutants using TPP+ was proposed as a methodology to assess the photodegradation extent. In the last chapter of Part I, Chapter 5, TPTP+ is used to stablish the best characteristics of a photocatalyst. Besides, the study claimed the influence of the concentration of the target substances in the efficiency of the excited states or, in general, of the key short-lived intermediates. Secondly, in Part II, in Chapter 6, Rose Bengal, a typical photocatalyst used in wastewater remediation, known for working via Type II mechanism, was evaluated for the removal of two common drugs. In addition, a second one, Perinaphtenone, which exhibits even a higher singlet oxygen quantum yield than Rose Bengal was tested. In Chapter 7, NMQ+, a non-typical photocatalyst able of generate singlet oxygen from its singlet excited state, was used in the photooxidation of three different pollutants. In every case, the major contribution of Type I vs Type II mechanism was demonstrated. Finally, in Part III, Chapter 8 was devoted to the photocatalytic reduction of organic bromides. In this case, Riboflavine, a non-metallic organic dye, was used as a photocatalyst. Analogously, careful attention was paid to the behavoiur of the intermediates, which were in agreement, as well as to the thermodynamics of the steps involved in the photocatalytic cycle.Martínez Haya, R. (2018). Photoredox catalysis for environmental and chemical applications. A mechanistically-based approach [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/114828TESI

Reinventing the De Mayo reaction: synthesis of 1,5-diketones or 1,5-ketoesters via visible light [2+2] cycloaddition of beta-diketones or beta-ketoesters with styrenes

[EN] A visible light mediated De Mayo reaction between 1,3-diketones and styrenes following a [2+2] cycloaddition pathway via a photosensitization mechanism gives access to 1,5-diketones. The reaction has been applied to substituted styrenes and aryl- and alkyl-substituted ketones. Moreover, the method converts -ketoesters, -amido esters, and -cyano ketones. Seven membered rings, a frequent structural motif of natural products, are also accessible using this methodology.This work was supported by the Deutsche Forschungsgemein-schaft DFG (GRK 1626, Chemical Photocatalysis). L. M. thanks the Alexander von Humboldt foundation for a postdoctoral fellowship. R. M.-H. thanks the DAAD for a short-term research grant. We thank Ms Regina Hoheisel (University of Regensburg) for her assistance in cyclic voltammetry measurements.Martínez-Haya, R.; Marzo, L.; König, B. (2018). 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Type I vs Type II photodegradation of pollutants

[EN] Rose Bengal (RB) is a widely used photocatalyst due to its high quantum yield of singlet oxygen (O-1(2)) formation. Hence, when RB has been employed for wastewater remediation, the observed photodegradation has been attributed to reaction between the pollutants and the O-1(2) formed (Type II mechanism). However, RB could also react, in principle, via electron transfer (Type I mechanism). Herein, competition between Type I vs Type II oxidation has been investigated for RB in the photodegradation of emerging pollutants such as diclofenac (DCF) and acetaminophen (ACP). In parallel, the photocatalyst perinaphthenone (PN) has also been evaluated for comparison. The degree of removal achieved for both pollutants in aerated/deaerated aqueous solutions irrespective of the employed photocatalyst does not support the involvement of O-1(2) as the main species responsible for removal of the pollutants. Photophysical experiments showed that the triplet excited states of RB and PN are efficiently quenched by both DCF and ACP. Moreover, O-1(2) emission was also quenched by DCF and ACP. Thus the contribution of Type I versus Type II in the photodegradation has been evaluated from the experimentally determined rate constants. Nevertheless, at the upper limit for the typical concentration of emerging pollutants (10(-5) M) photodegradation proceeds mainly via Type I mechanism.Financial support from Spanish Government (Grants SEV-2016-0683 and CTQ2012-38754-C03-03) and Generalitat Valenciana (Prometeo Program) is gratefully acknowledged. We also thank support from VLC/Campus. R. Martinez-Haya thanks financial support from Spanish Government (Grant SEV-2012-0267).Martínez-Haya, R.; Miranda Alonso, MÁ.; Marín García, ML. (2018). Type I vs Type II photodegradation of pollutants. Catalysis Today. 313:161-166. https://doi.org/10.1016/j.cattod.2017.10.034S16116631

Heterogeneous riboflavin-based photocatalyst for pollutant oxidation through electron transfer processes

[EN] Organic photocatalysts could employ visible light to produce photodegradation of pollutants; however, their low photostability prevents their reuse even when they are supported on solid materials. Herein, to obtain a Riboflavin (RF)-based photocatalyst robust and recyclable, RF has been covalently anchored to silica particles, converting the known homogeneous photocatalyst into a new heterogeneous one (SiO2-RF). To enhance the photostability of SiO2-RF, generation of the RF triplet excited state and subsequent singlet oxygen were prevented by ensuring a complete shell of RF moieties on the silica spheres. Moreover, adsorption of organic pollutants such as phenol, ortho-phenylphenol, 2,4,6-trichlomphenol and pentachlorophenol on the surface of SiO2-RF is favored in aqueous media, facilitating electron transfer from the pollutants to the short-lived first singlet excited state of RF. Photophysical measurements provided evidence on the photocatalytic mechanism for SiO2-RF.YY The authors would like to acknowledge H2020/Marie Skodowska-Curie Actions under the AQUAlity project (Reference: 765860) , Con-selleria d'Educacio, Investigacio, Cultura i Esport (PROMETEO/2017/075) , the Spanish Ministry of Science, Innovation and Universities (PID2019-110441RB-C33 and SEV-2016-0683) . O. Cabezuelo is indebted to the Universitat Polite cnica de Valencia for the Predoctoral FPI fellowship (FPI-UPV/Subprograma 1) . R. M.-H. acknowledges Fondo Social Europeo (FSE) 2014-2020 Generalitat Valenciana (APOSTD-2019/124) .Cabezuelo-Gandia, O.; Martínez-Haya, R.; Montes, N.; Bosca Mayans, F.; Marín García, ML. (2021). Heterogeneous riboflavin-based photocatalyst for pollutant oxidation through electron transfer processes. Applied Catalysis B Environmental. 298:120497-120510. https://doi.org/10.1016/j.apcatb.2021.120497S12049712051029

A mechanistic study on the potential of quinolinium salts as photocatalysts for the abatement of chlorinated pollutants

[EN] Photocatalytic degradation of three highly chlorinated contaminants, namely 2,4,6-trichlorophenol (TCP), 2,4,6-trichloroanisole (TCA) and 5-chloro-2-(2,4-dichlorophenoxy)phenol (triclosan, TCS) has been investigated in the presence of N-methylquinolinium tetrafluoroborate (NMQ(+)), a photocatalyst able to act via Type I or Type II mechanism. Photodegradation of contaminants under aerobic conditions was achieved within hours; and it was accompanied by mineralization, as demonstrated by trapping of the evolved carbon dioxide as barium carbonate. Moreover, a high degree of detoxification, based on % inmobilization of daphnids (Daphnia magna bioassay), was reached after 70 h of irradiation. Quenching of the NMQ(+) fluorescence by the pollutants was evidenced by a decrease in the emission intensity and lifetime. Detection of the reduced NMQ. by laser flash photolysis in the presence of the pollutants provided an unambigous evidence of the electron transfer process. Quenching of singlet oxygen by the contaminants showed the typical singlet oxygen quenching constants (10(5)-10(6) M-1 s(-1)). Evaluation of the relative contribution of both pathways (Type I vs Type II) point to the photodegradation occurring via a Type I mechanism, being the contribution of Type II mechanism negligible at any concentration range.Financial support from Spanish Government (Grant SEV-2016.0683 and CTQ2015-69832-C4) and generous contribution from Generalitat Valenciana (Prometeo Program) are gratefully acknowledged. We also thank support from VLC/Campus. R Martinez-Haya thanks financial support from Spanish Government (Grant SEV-2012-0267).Martínez-Haya, R.; Sabater Marco, C.; Castillo López, M.; Miranda Alonso, MÁ.; Marín García, ML. (2018). A mechanistic study on the potential of quinolinium salts as photocatalysts for the abatement of chlorinated pollutants. Journal of Hazardous Materials. 351:277-284. https://doi.org/10.1016/j.jhazmat.2018.03.010S27728435

Direct detection of the triphenylpyrylium-derived short-lived intermediates in the photocatalyzed degradation of acetaminophen, acetamiprid, caffeine and carbamazepine

[EN] Advanced oxidation processes are useful methodologies to accomplish abatement of contaminants; however, elucidation of the reaction mechanisms is hampered by the difficult detection of the short-lived primary key species involved in the photocatalytic processes. Nevertheless, herein the combined use of an organic photocatalyst such as triphenylpyrylium (TPP+) and photophysical techniques based on emission and absorption spectroscopy allowed monitoring the photocatalyst-derived short-lived intermediates. This methodology has been applied to the photocatalyzed degradation of different pollutants, such as acetaminophen, acetamiprid, caffeine and carbamazepine. First, photocatalytic degradation of a mixture of the pollutants showed that acetaminophen was the most easily photodegraded, followed by carbamazepine and caffeine, being the abatement of acetamiprid almost negligible. This process was accompanied by mineralization, as demonstrated by trapping of carbon dioxide using barium hydroxide. Then, emission spectroscopy measurements (steady-state and time-resolved fluorescence) allowed demonstrating quenching of the singlet excited state of TPP+. Laser flash photolysis experiments with absorption detection showed that oxidation of contaminants is accompanied by TPP+ reduction, with formation of a pyranyl radical (TPP center dot), that constituted a fingerprint of the redox nature of the occurring process. The relative amounts of TPP center dot detected was also correlated with the efficiency of the photodegradation process.Financial support from Spanish Government (Grants SEV-2016-0683, CTQ2012-38754-C03-02 and CTQ2015-69832-C4-4-R) and Generalitat Valenciana (Prometeo Program) is gratefully acknowledged. R. Martinez-Haya thanks financial support from Spanish Government (Grant SEV-2012-0267).Martínez-Haya, R.; Gomis Vicens, J.; Arqués Sanz, A.; Amat Payá, AM.; Miranda Alonso, MÁ.; Marín García, ML. (2018). Direct detection of the triphenylpyrylium-derived short-lived intermediates in the photocatalyzed degradation of acetaminophen, acetamiprid, caffeine and carbamazepine. Journal of Hazardous Materials. 356:91-97. https://doi.org/10.1016/j.jhazmat.2018.05.023S919735

Degradación de contaminantes de la industria del corcho fotocatalizada por sales de pirilio y tiapirilio. Estudios fotoquímicos y fotofísicos

Martínez Haya, R. (2014). Degradación de contaminantes de la industria del corcho fotocatalizada por sales de pirilio y tiapirilio. Estudios fotoquímicos y fotofísicos. http://hdl.handle.net/10251/53767Archivo delegad

Una perspectiva histórica y epistemológica de los estudios de ciencia y género y su uso en el aula de ciencias

[ES] En los años 60 del pasado siglo y en consonancia con la segunda ola del feminismo, surgen los primeros estudios de ciencia y género. Estos estudios abarcan diferentes enfoques que relacionan la presencia de la mujer en la ciencia, bien sea bajo la figura de científicas o como sujetos a estudiar biológica o psicológicamente; identificando una marcada desigualdad entre hombres y mujeres desde cualquier enfoque. El estudio y la repercusión de este desequilibrio han establecido un área de investigación conocida cómo ciencia y género, cuyos análisis son cada vez más influyentes en el mundo de la ciencia y la docencia.[EN] In the decade of the 60¿s of the last century and in line with the second wave of the feminism, the firsts studies based on science and gender appeared. These studies include several approaches which correlate the women presence on science, as scientists or as biologically or psychologically subjects to study, revealing a noticeable inequality between men and women from any approach. The study and the repercussion of this inequality have stablished a research field known as science and gender, whose analysis are becoming more influent in the science and teaching world.Martínez-Haya, R. (2019). Una perspectiva histórica y epistemológica de los estudios de ciencia y género y su uso en el aula de ciencias. Anales de Química. 115(1):26-30. http://hdl.handle.net/10251/1533772630115

Investigation of new hydrophilic epoxy networks and hydrogels from them

Consulta en la Biblioteca ETSI Industriales (9132)[ES] The aim of this project is to carry out the "Proyecto Final de Carrera" (PFC) as the last step to finish my Chemical Engineering degree at the Escuela Técnica Superior de Ingenieros Industriales of the Universidad Politécnica de Valencia. The engineering and scientific objective of the project is based on the synthesis, development and study of new hydrophilic epoxy networks based on commercially available Jeffamines and a cross -linker agent, poly(propyleneglycol) diglycidyl ether, and hydrogels prepared from them. These kind of materials present very interesting characteristics such as they are able to absorb a big amount of water in their macromolecular network without dissolving. Actually, this project is a part of a greater magnitude study whose purpose is analyzing epoxy networks to check their suitability and capacity for medical applications. The direction of the project has been made by Dr. D. Ivan Krakovsky representing the Department of Macromolecular Physics of the Mathematics and Physics Faculty of the Charles University of Prague, in order to develop and study biocompatible materials with biomedical applications.Martínez Haya, R. (2012). Investigation of new hydrophilic epoxy networks and hydrogels from them. http://hdl.handle.net/10251/28765.Archivo delegad

Degradación de contaminantes de la industria del corcho fotocatalizada por sales de pirilio y tiapirilio. Estudios fotoquímicos y fotofísicos

Martínez Haya, R. (2014). Degradación de contaminantes de la industria del corcho fotocatalizada por sales de pirilio y tiapirilio. Estudios fotoquímicos y fotofísicos. http://hdl.handle.net/10251/53767Archivo delegad