Transient absorption spectroscopic studies on 4-nitroquinoline N-oxide: From femtoseconds to microseconds timescale

[EN] The singlet excited state of 4-nitroquinoline N-oxide ((1)NQNO*) has been characterized by different spectroscopic techniques, combining transient absorption with steady state and time-resolved emission spectroscopy. The energy of (1)NQNO* has been established as 255 kJ/mol from the fluorescence spectrum, whereas its lifetime has been found to be 10 ps in the femto-laser flash photolysis (LFP) experiments, where a characteristic S-1-S-n absorption band with maximum centered at 425 nm is observed. In a first stage, the triplet excited state of NQNO ((3)NQNO*) has also been characterized by emission spectroscopy in solid matrix, at low temperature. Thus, from the steady state phosphorescence spectrum the triplet energy has been estimated as 183 kJ/mol, whereas the setup with time resolution has allowed us to determine the phosphorescence lifetime as 3 ms. Formation of (3)NQNO* by intersystem crossing in solution at room temperature, has been monitored by femto-LFP, which shows the appearance of a band with maximum at 560 nm (T-1-T-n). It increases with the decreasing intensity of its precursor 425 nm(S-1-S-n) band, giving rise to an isosbestic point at 500 nm. The characterization of (3)NQNO* has been completed by nano-LFP, using xanthone as photosensitizer and oxygen as well as beta-carotene as quenchers. In addition, quenching of (3)NQNO* by electron donors (DABCO) is also observed in aprotic solvents, leading to the radical anion of NQNO (.(-)NQNO). If there is a proton source in the medium (Et3N as electron donor or MeCN:H2O/4:1 as solvent system) protonation of the radical anion results in formation of the neutral radical of NQNO (.NQNOH). In general, all processes are slower in protic solvents because of the solvation sphere. Overall, this information provides a deeper insight into the formation and behavior of excited states and radical ionic species derived from the title molecule NQNO. (C) 2019 Elsevier B.V. All rights reserved.The work was financially supported by the Regional Government of Generalitat Valenciana (PROMETEO/2017/075) as well as the Spanish Government Science Department with the CTQ-2016-78875-P and CTQ-2009-13699 projects and the N. D.-G. fellowship (BES-2010-035875). BC, CC and FE acknowledge MIUR and the University of Perugia for financial support to the project AMIS, through the program "Dipartimenti di Eccellenza - 2018-2022"Duran-Giner, N.; Carlotti, B.; Clementi, C.; Elisei, F.; Encinas Perea, S.; Miranda Alonso, MÁ. (2019). Transient absorption spectroscopic studies on 4-nitroquinoline N-oxide: From femtoseconds to microseconds timescale. 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Aerobic Visible-Light-Driven Borylation of Heteroarenes in a Gel Nanoreactor

[EN] Heteroarene boronate esters constitute valuable intermediates in modern organic synthesis. As building blocks, they can be further applied to the synthesis of new materials, since they can be easily transformed into any other functional group. Efforts toward novel and efficient strategies for their preparation are clearly desirable. Here, we have achieved the borylation of commercially available heteroarene halides under very mild conditions in an easy-to-use gel nanoreactor. Its use of visible light as the energy source at room temperature in photocatalyst-free and aerobic conditions makes this protocol very attractive. The gel network provides an adequate stabilizing microenvironment to support wide substrate scope, including furan, thiophene, selenophene, and pyrrole boronate esters.Financial support from the Generalitat Valenciana (CIDEGENT/2018/044) and the Spanish Ministry of Science and Innovation (PID2019-105391GB-C21, PID2019-105391GBC22, BEAGAL18/00166, and BES-2017-080215) is gratefully acknowledged. We thank the Electron Microscopy Service from the UPV and Prof. Julia Perez-Prieto for spectroscopy facilities. D.D.D. also thanks NANOtec, INTech, Cabildo de Tenerife, and ULL for laboratory facilities.Herrera-Luna, JC.; Díaz Díaz, D.; Abramov, A.; Encinas Perea, S.; Jiménez Molero, MC.; Pérez-Ruiz, R. (2021). Aerobic Visible-Light-Driven Borylation of Heteroarenes in a Gel Nanoreactor. Organic Letters. 23(6):2320-2325. https://doi.org/10.1021/acs.orglett.1c004512320232523

Solar filters as feasible acceptors of atomic oxygen

The triazine derivative Tinosorb S has been shown to accept atomic oxygen generated by N-oxide photodeoxygenation. This is a unique example of a solar filter and mechanism-directed antioxidant. The concept has been proved by a combination of steady-state and laser-flash photolysis.We thank the Spanish Government (Project CTQ2009-13699 and fellowship to N. D.-G.) for financial support.Durán Giner, EDLN.; Encinas Perea, S.; Miranda Alonso, MÁ. (2013). Solar filters as feasible acceptors of atomic oxygen. Photochemical & Photobiological Sciences. 12(5):725-728. https://doi.org/10.1039/c3pp25407kS72572812

QUÍMICA PARA INGENIERÍA. PROBLEMAS Y PRÁCTICAS

El texto "Química para Ingeniería. Problemas y Prácticas" está dirigido a los estudiantes que cursan la asignatura de Química en cualquier titulación de Grado de Ingeniería. Consta de dos partes. La primera contiene una serie de capítulos dedicados a la resolución de unos doscientos problemas relacionados con termodinámica y equilibrios, cinética, procesos de oxidación y reducción, hidrocarburos saturados e insaturados, hidrocarburos aromáticos, alcoholes, éteres y epóxidos, aldehídos y cetonas, y ácidos carboxílicos y derivados. Cada capítulo consta de una serie de problemas resueltos, que ayudan a repasar y reafirmar los conceptos adquiridos en las clases teóricas, y una colección de problemas representativos, aportando su resultado numérico, con el fin de estimular al alumno a su resolución. Finalmente, se incluyen problemas propuestos para resolverlos en grupos de trabajo, con el objetivo de fomentar el trabajo cooperativo y que el alumno adquiera las habilidades de trabajo en equipo, que le serán de gran utilidad en su futura labor profesional. En la segunda parte se incluyen seis prácticas de laboratorio que tratan de la determinación del calor de una reac-ción, el montaje y estudio de una celda galvánica, electrolítica y de combustible hidrógeno-oxígeno, preparación de polímeros y obtención de ésteres utilizados como saborizantes, entre otras.Climent Olmedo, MJ.; Encinas Perea, S.; Ferrer Ribera, RB.; Iborra Chornet, S.; Marín García, ML.; Morera Bertomeu, IM.; Navalón Oltra, S.... (2013). QUÍMICA PARA INGENIERÍA. PROBLEMAS Y PRÁCTICAS. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/70956EDITORIA

QUÍMICA PARA INGENIERÍA

Este texto contiene los conceptos de Química General, Inorgánica y Orgánica imprescindibles para la formación del estudiante de Ingeniería. Es una recopilación de los contenidos que se desarrollan en las clases teóricas y tiene como objetivo guiar al alumno en el aprendizaje de la Química. Se incluyen, entre otros, conceptos relacionados con la generación de energía mediante el uso de combustibles fósiles y las alternativas a los mismos, las celdas de combustible, la protección contra la corrosión, la obtención y utilización de los diferentes polímeros, y los procesos químicos catalíticos. Va dirigido a los alumnos de primer curso de las titulaciones de Grado de Ingeniería en Organización Industrial, en Tecnologías Industriales y en Energía, impartidas en la ETSII, aunque puede ser utilizado en cualquier Grado de Ingeniería donde se precise tener una formación básica para relacionar los principios de la Química con los fenómenos comunes observables y su aplicación a la industria, a la tecnología y al medio ambiente.Climent Olmedo, MJ.; Encinas Perea, S.; Ferrer Ribera, RB.; Iborra Chornet, S.; Marín García, ML.; Morera Bertomeu, IM.; Navalón Oltra, S.... (2011). QUÍMICA PARA INGENIERÍA. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/71999EDITORIA