Molecular Water Oxidation Catalysts Based on Copper and Nickel Complexes

Aquesta Tesi Doctoral es centra en l’estudi de catalitzadors moleculars per a l’oxidació d’aigua basats en coure i níquel, ja que la seva gran abundància i baix cost els fa potencials candidats pel seu ús en sistemes catalítics. Tot i així, avui en dia hi ha una important mancança d’informació respecte als seus mecanismes de reacció i els factors que influeixen la seva activitat. Per això, en primer lloc, es desenvolupen nous catalitzadors moleculars basats en el coure com a centre metàl·lic. L’estudi mecanístic d’aquests catalitzadors revela l’important rol que té l’oxidació del lligand en el cicle catalític a l’hora de controlar el sobre-potencial de la reacció. Al mateix temps, en col·laboració amb el grup del Professor Maseras (ICIQ) es descobreix un nou mecanisme per a la formació de l’enllaç oxigen-oxigen que opera en diferents tipus catalitzadors de coure. Aquest nou mecanisme sense precedents permet redefinir l’escenari mecanístic per a l’oxidació d’aigua. Posteriorment, es realitza el disseny de nous lligands amb diferents propietats redox que permeten estudiar factors que influeixen en l’activitat i el mecanisme de reacció. Això proporciona informació rellevant per al disseny de nous catalitzadors més actius, estables i eficients. També s’aborda la immobilització dels catalitzadors desenvolupats sobre els elèctrodes basats en grafè. D’aquesta manera es descobreix el paper essencial que té la deslocalització d’electrons en els orbitals π, que permet incrementar la cinètica de la reacció per més de dues ordres de magnitud. Finalment, el coneixement generat en coure s’intenta expandir per a la seva aplicació en els catalitzadors de níquel. Això permet estudiar el caràcter làbil dels complexos de níquel en medis bàsics, que determina la presència de dos mecanismes d’operació basats en espècies moleculars i òxids de níquel respectivament.Esta Tesis Doctoral se centra en el estudio de catalizadores moleculares para la oxidación de agua basados en cobre y níquel, ya que su gran abundancia y su bajo coste los hace potenciales candidatos para su uso en sistemas catalíticos. A pesar de esto, hoy en día hay una importante carencia de información con respecto a sus mecanismos de reacción y los factores que determinan su actividad. Por ello, en primer lugar, se desarrollan nuevos catalizadores moleculares basados en cobre como centro metálico. El estudio mecanístico de dichos catalizadores revela el importante rol que tiene la oxidación del ligando en el ciclo catalítico a la hora de controlar el sobre-potencial de la reacción. Al mismo tiempo, en colaboración con el grupo del Profesor Maseras (ICIQ) se descubre un nuevo mecanismo para la formación del enlace oxígeno-oxígeno que opera en diferentes tipos de catalizadores de cobre. Este nuevo mecanismo sin precedentes permite redefinir el escenario mecanístico para la oxidación de agua. Posteriormente, se realiza el diseño de nuevos ligandos con diferentes propiedades redox que permiten estudiar los factores que influyen en la actividad y el mecanismo de reacción. Esto proporciona información relevante para el diseño de nuevos catalizadores más activos, estables y eficientes. También se aborda la inmovilización de los catalizadores desarrollados sobre electrodos basados en grafeno. De esta forma se descubre el papel esencial que tiene la deslocalización de electrones en orbitales π, que permite incrementar la cinética de reacción por más de dos órdenes de magnitud. Finalmente, el conocimiento generado en cobre se intenta expandir para su aplicación en catalizadores de níquel. Esto permite estudiar el carácter lábil de los complejos de níquel en medios básicos, que determina la presencia de dos mecanismos de operación basados en especies moleculares y óxidos de níquel respectivamente.This Doctoral Thesis focuses on the study of molecular catalysts for water oxidation based on copper and nickel since their high abundance and inexpensive character make them potential candidates for their use in catalytic systems. Despite that, there is a current lack of information regarding their reaction mechanism and the factors that determine their activity. Therefore, we first develop new molecular catalysts based on copper as metal center. Their mechanistic study reveals the essential role that the ligand oxidation has in the catalytic cycle as tool to control the reaction overpotential. In collaboration with Prof. Maseras group (ICIQ) a new mechanism for the oxygen-oxygen bond formation is found to operate in different copper catalysts. This unprecedented mechanism allows us to redefine the mechanistic scenario in water oxidation. Later on, the design of new ligands with different redox properties is addressed. That allows to study the factors that have influence on the activity and reaction mechanism and provide valuable information for the design of more active, stable and efficient new catalysts. Moreover, the immobilization of the molecular catalyst on the surface of graphene-based electrodes is also studied. We discover the essential role of the π-delocalization in increasing the reaction kinetic by more than two orders of magnitude. Finally, the knowledge developed with copper complexes is applied in nickel catalysis. This allows to study the labile character of nickel complexes in basic media that determine the presence of two different operating mechanism based on molecular species and nickel oxides respectively

Electrocatalytic Ammonia Oxidation Mediated by a Polypyridyl Iron Catalyst

Electrocatalytic ammonia oxidation (AO) mediated by iron(II) tris(2-pyridylmethyl)amine (TPA) bis-ammine triflate, [(TPA)Fe(NH₃)₂]OTf₂, is reported. Interest in (electro)catalytic AO is growing rapidly, and this report adds a first-row transition metal (iron) complex to the known Ru catalysts recently reported. The featured system is well behaved and has been studied in detail by electrochemical methods. Cyclic voltammetry experiments in the presence of ammonia indicate an onset potential corresponding to ammonia oxidation at 0.7 V vs Fc/Fc⁺. Controlled potential coulometry (CPC) at an applied bias of 1.1 V confirms the generation of 16 equiv of N₂ with a Faradaic efficiency for N₂ of ∼80%. Employing ¹⁵NH₃ yields exclusively ³⁰N₂, demonstrating the conversion of ammonia to N₂. A suite of electrochemical studies is consistent with an initial EC step that generates an Fe^(III)–NH₂ intermediate (at 0.4 V) followed by an anodically shifted catalytic wave. The data indicate a rate-determining step that is first order in both [Fe] and [NH₃] and point to a fast catalytic rate (k_(obs)) of ∼10⁷ M⁻¹·s⁻¹ as computed by foot of the wave analysis (FOWA)

Electrocatalytic Ammonia Oxidation Mediated by a Polypyridyl Iron Catalyst

Electrocatalytic ammonia oxidation (AO) mediated by iron(II) tris(2-pyridylmethyl)amine (TPA) bis-ammine triflate, [(TPA)Fe(NH₃)₂]OTf₂, is reported. Interest in (electro)catalytic AO is growing rapidly, and this report adds a first-row transition metal (iron) complex to the known Ru catalysts recently reported. The featured system is well behaved and has been studied in detail by electrochemical methods. Cyclic voltammetry experiments in the presence of ammonia indicate an onset potential corresponding to ammonia oxidation at 0.7 V vs Fc/Fc⁺. Controlled potential coulometry (CPC) at an applied bias of 1.1 V confirms the generation of 16 equiv of N₂ with a Faradaic efficiency for N₂ of ∼80%. Employing ¹⁵NH₃ yields exclusively ³⁰N₂, demonstrating the conversion of ammonia to N₂. A suite of electrochemical studies is consistent with an initial EC step that generates an Fe^(III)–NH₂ intermediate (at 0.4 V) followed by an anodically shifted catalytic wave. The data indicate a rate-determining step that is first order in both [Fe] and [NH₃] and point to a fast catalytic rate (k_(obs)) of ∼10⁷ M⁻¹·s⁻¹ as computed by foot of the wave analysis (FOWA)

Redox Metal-Ligand Cooperativity Enables Robust and Efficient Water Oxidation Catalysis at Neutral pH with Macrocyclic Copper Complexes

Water oxidation catalysis stands out as one of the most important reactions to design practical devices for artificial photosynthesis. Use of late first-row transition metal (TM) complexes provides an excellent platform for the development of inexpensive catalysts with exquisite control on their electronic and structural features via ligand design. However, the difficult access to their high oxidation states and the general labile character of their metal–ligand bonds pose important challenges. Herein, we explore a copper complex (1²⁻) featuring an extended, π-delocalized, tetra-amidate macrocyclic ligand (TAML) as water oxidation catalyst and compare its activity to analogous systems with lower π-delocalization (2²⁻ and 3²⁻). Their characterization evidences a special metal–ligand cooperativity in accommodating the required oxidative equivalents using 1²⁻ that is absent in 2²⁻ and 3²⁻. This consists of charge delocalization promoted by easy access to different electronic states at a narrow energy range, corresponding to either metal-centered or ligand-centered oxidations, which we identify as an essential factor to stabilize the accumulated oxidative charges. This translates into a significant improvement in the catalytic performance of 1²⁻ compared to 2²⁻ and 3²⁻ and leads to one of the most active and robust molecular complexes for water oxidation at neutral pH with a k_(obs) of 140 s⁻¹ at an overpotential of only 200 mV. In contrast, 2²⁻ degrades under oxidative conditions, which we associate to the impossibility of efficiently stabilizing several oxidative equivalents via charge delocalization, resulting in a highly reactive oxidized ligand. Finally, the acyclic structure of 3²⁻ prevents its use at neutral pH due to acidic demetalation, highlighting the importance of the macrocyclic stabilization

Faster monitoring of the invasive alien species (IAS) Dreissena polymorpha in river basins through isothermal amplification

Zebra mussel (Dreissena polymorpha) is considered as one of the 100 most harmful IAS in the world. Traditional detection methods have limitations, and PCR based environmental DNA detection has provided interesting results for early warning. However, in the last years, the development of isothermal amplification methods has received increasing attention. Among them, loop-mediated isothermal amplification (LAMP) has several advantages, including its higher tolerance to the presence of inhibitors and the possibility of naked-eye detection, which enables and simplifies its potential use in decentralized settings. In the current study, a real-time LAMP (qLAMP) method for the detection of Dreissena polymorpha was developed and tested with samples from the Guadalquivir River basin, together with two real-time PCR (qPCR) methods using different detection chemistries, targeting a specific region of the mitochondrial gene cytochrome C oxidase subunit I. All three developed approaches were evaluated regarding specificity, sensitivity and time required for detection. Regarding sensitivity, both qPCR approaches were more sensitive than qLAMP by one order of magnitude, however the qLAMP method proved to be as specific and much faster being performed in just 9 min versus 23 and 29 min for the qPCR methods based on hydrolysis probe and intercalating dye respectivelyThis work was supported by a partnership agreement project between the Confederación Hidrográfica del Guadalquivir and INL for the development of a system for early detection of zebra mussels through analysis of environmental DNA, and by project Nanotechnology Based Functional Solutions (NORTE-01-0145-FEDER-000019), supported by Norte Portugal Regional Operational Programme (NORTE2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund. S. A. acknowledges the Portuguese funding institution FCT – Fundação para Ciência e Tecnologia for Ph.D. scholarship SFRH/BD/140396/2018S

Unravelling the Mechanistic Pathway of the Hydrogen Evolution Reaction Driven by a Cobalt Catalyst

Acord transformatiu CRUE-CSICA cobalt complex bearing a κ-NP ligand is presented (1 or Co(L), where L is (1E,1'E)-1,1'-(pyridine-2,6-diyl)bis(N-(3-(diphenylphosphanyl)propyl)ethan-1-imine). Complex 1 is stable under air at oxidation state Co thanks to the π-acceptor character of the phosphine groups. Electrochemical behavior of 1 reveals a two-electron Co/Co oxidation process and an additional one-electron reduction, which leads to an enhancement in the current due to hydrogen evolution reaction (HER) at E=−1.6 V vs Fc/Fc. In the presence of 1 equiv of bis(trifluoromethane)sulfonimide, 1 forms the cobalt hydride derivative Co(L)-H (2), which has been fully characterized. Further addition of 1 equiv of CoCp* (Cp* is pentamethylcyclopentadienyl) affords the reduced Co(L)-H (2) species, which rapidly forms hydrogen and regenerates the initial Co(L) (1). The spectroscopic characterization of catalytic intermediates together with DFT calculations support an unusual bimolecular homolytic mechanism in the catalytic HER with 1

CIBERER : Spanish national network for research on rare diseases: A highly productive collaborative initiative

Altres ajuts: Instituto de Salud Carlos III (ISCIII); Ministerio de Ciencia e Innovación.CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on rare diseases (RDs) currently consists of 75 research groups belonging to universities, research centers, and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical, and cellular research of RDs. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this article, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions toward the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to RD research

Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study

PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks

Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.

PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks