http://hdl.handle.net/10256/1551 2025-09-29T09:02:48Z http://hdl.handle.net/10256/27391 Low-load Θ-metallacarboranes as safe and efficient photoredox catalysts for UVA-driven oxidation in water Guerrero Troyano, Isabel; Abdelgawwad, Abdelazim M.A.; Viñas Teixidor, Clara; Roca Sanjuán, Daniel; Francés-Monerris, Antonio; Romero García, Isabel; Teixidor Bombardó, Francesc Transition-metal (TM) ions 4d6 or 5d6 configurations, typically used in photoredox catalysis, are often rare and expensive. In contrast, abundant first-row TM ions tend to favour metal-centered excited states, limiting their practical photocatalytic use. Here, we present two efficient 3d6 and 3d5 photoredox catalysts, [3,3'-Co(1,2-C2B9H11)2]- and [3,3'-Fe(1,2-C2B9H11)2]-, with identical structures and charges (-1). Despite different electronic configurations, both catalysts deliver comparable performances in alcohol and alkene oxidation in water, even at low catalyst loadings (0.01 mol%). The catalysts are designed to operate in water without additional cosolvents thanks to the surfactant properties of both θ-metallacarboranes. The impact of irradiating wavelength, explored through quantum chemistry, rationalizes their photocatalytic outcomes. Remarkably, 3d5 or 3d6 systems can match or outperform heavier TM analogues when supported by boron-based ligands, though selectivity differences highlight the role of metal electronic structure. UVA irradiation significantly boosts [o-COSAN]⁻ activity, offering new design insights for earth-abundant photoredox catalysts 2025-09-17T00:00:00Z http://hdl.handle.net/10256/27354 Macrocyclic NHC Ligands in Hoveyda-Type Ru Alkene Metathesis Catalysts: Only Sterics? Brotons Rufes, Artur; Posada-Pérez, Sergio; Diver, Steven T.; Poater Teixidor, Albert The integration of macrocyclic structures within N-heterocyclic carbene (NHC) ligands in Hoveyda-type catalysts presents a pioneering strategy to enhance selectivity in cross-alkene metathesis. This approach falls within a promising paradigm for avoiding undesired homocouplings between reacting alkenes and introducing site-selectivity into the cross metathesis process. This paper presents a computational study that aims to provide an improved understanding of the impact of these ligand modifications on stability, sterics, and activity, focusing on the precatalyst activation and cross-metathesis. The traditional Hoveyda-type catalyst is compared alongside two recent macrocyclic systems for which experimental data is available. Higher activation barriers in the macrocyclic systems are consistent with the reduced activity observed in these systems. Additionally, a noncovalent interaction component was found to facilitate the selective pathway, in conjunction with the already expected steric descriptors. These results highlight the potential of macrocyclic NHC ligands to enhance catalyst performance, not only offering chemoselectivity based on alkene size, but a potential for stereoselectivity capacity arising from the macrocycle-induced electronic effects 2025-09-15T00:00:00Z http://hdl.handle.net/10256/27331 Characterization of σ and π reaction channels in hydrogen atom transfer reactions Ahsan, Faiza; Ansari, Mursaleem; Klein, Johannes E.M.N.; Swart, Marcel C(sp3) –H bond activation mechanisms typically involve σ- and π-channel pathways, as characterized by FeOH (or FeOC) angles of ca. 180° and 120°, respectively. It is well known that the preference for either the σ- or π-channel depends on the spin state, but doubts exist on what would be characteristic values for the FeOX (X = H or C) angles. Here we study the oxidation of methane and ethane mediated by an Fe(IV)oxo model complex through density functional theory. A systematic comparison of dispersion-corrected B3LYP (B3LYP-D2, B3LYP-D3, B3LYP-D3BJ, B3LYP-D4) and the uncorrected counterpart (B3LYP) was conducted to evaluate the role of dispersion interactions in both gas and solvent phases. Our results reveal that dispersion corrections significantly influence barriers at transition states (TSs), particularly in the solvent phase, where dispersion contributions enhance stabilization of TS structures. The σ-channel pathway dominates for high spin (S = 2), while intermediate spin (S = 1) states favor the π-channel. Dispersion effects were found to be more pronounced for ethane, where larger non-covalent interactions between the substrate and Fe(IV)oxo complex arise. The FeOX angles vary substantially depending on the choice of dispersion correction, and between gas phase and solution phase. Indeed, for the reaction with ethane the FeOX values of the σ-channel approach values that are typically associated with the π-channel. Fortunately, the Spin-Resolved Charge Displacement Function provides a clear visual tool to distinguish the two channels. These insights advance the understanding of hydrocarbon functionalization by high-valent iron-oxo species, with implications for synthetic catalyst design in homogeneous and enzymatic catalysis 2025-11-01T00:00:00Z http://hdl.handle.net/10256/27322 Evaluation of the quantitative performance of different spectroscopic techniques for multielemental analysis of nail and hair samples: A comparative study Silva, João; Marguí Grabulosa, Eva; Guillemaut, Romain; Jablan, Jasna; Migliori, Alessandro; Kasprzyk, Paula; Ferreira, Joaquim J.; Pessanha, Sofia Background: The accurate detection and quantification of elemental content in skin appendages, such as, hair and nails are pivotal in biomedical research, including disease diagnostics, environmental exposure monitoring, and forensic investigations. Methods: This study evaluates and compares the suitability of different sample treatments and four spectroscopic techniques—Energy Dispersive X-ray Fluorescence (EDXRF), Total Reflection X-ray Fluorescence (TXRF), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) for multielemental analysis of these biological tissues. Making use of different Certified Reference Materials (CRMs), the performance of the developed methods was assessed based on their sensitivity, precision, range of detectable elements, and the extent of sample preparation required. Results: EDXRF method is suited for rapid and non-destructive determination of light elements present at relatively high concentrations – Sulfur (S), Chlorine (Cl), Potassium (K) and Calcium (Ca) – in hair and nail samples. TXRF provides information of most of the elements present in the target samples, including Bromine (Br), but the determination of light element (i.e, Phosphorus (P), S, Cl) is not feasible. Finally, the proposed ICP-OES/ICP-MS method is useful for the determination of major, minor and trace elements, except chlorine. Conclusion: This comparative study reveals the distinct strengths, range of elements and suitable applications of each technique, providing a valuable framework for selecting appropriate methods based on specific analytical needs 2025-12-01T00:00:00Z