Publications by authors named "Ricardo Fernandez-Teran"

Donor-bridge-acceptor complexes (D-B-A) are important model systems for understanding of light-induced processes. Here, we apply two-color two-dimensional infrared (2D-IR) spectroscopy to D-B-A complexes with a -Pt(II) acetylide bridge (D-C≡C-Pt-C≡C-A) to uncover the mechanism of vibrational energy redistribution (IVR). Site-selective C isotopic labeling of the bridge is used to decouple the acetylide modes positioned on either side of the Pt-center.

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There is a growing interest in developing dye-sensitized photocatalytic systems (DSPs) to produce molecular hydrogen (H ) as alternative energy source. To improve the sustainability of this technology, we replaced the sacrificial electron donor (SED), typically an expensive and polluting chemical, with an alcohol oxidation catalyst. This study demonstrates the first dye-sensitized system using a diketopyrrolopyrrole dye covalently linked to 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) based catalyst for simultaneous H evolution and alcohol-to-aldehyde transformation operating in water with visible irradiation.

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Article Synopsis
  • - The study analyzes the effects of conjugation and electronic properties on one-photon and two-photon absorption in a series of Re(I) carbonyl complexes with terpyridine ligands.
  • - A strong correlation between calculated and experimental two-photon absorption spectra was found, with notable cross sections of up to 40 GM in DMF for certain complexes.
  • - The researchers demonstrate that while conjugation and delocalization significantly enhance two-photon absorption, the excited state character does not directly improve non-linear properties, providing insights for future applications in photodynamic therapy and imaging.
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Over the last decades, photoreceptive proteins were extensively studied with biophysical methods to gain a fundamental understanding of their working mechanisms and further guide the development of optogenetic tools. Time-resolved infrared (IR) spectroscopy is one of the key methods to access their functional non-equilibrium processes with high temporal resolution but has the major drawback that experimental data are usually highly complex. Linking the spectral response to specific molecular events is a major obstacle.

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Article Synopsis
  • - Six rhenium(I) κ-dicarbonyl complexes with various electron-donating 4'-(4-substituted phenyl)terpyridine ligands were studied using techniques like transient IR, electrochemistry, and time-dependent density functional theory (TD-DFT) to understand their ground and excited states.
  • - These complexes showed broad absorption and stronger photoreductive abilities compared to similar tricarbonyl complexes, with parameters that correlated with Hammett σ substituent constants, indicating the influence of ligand structure on their electronic properties.
  • - The study revealed that the lowest excited states were metal-to-ligand charge-transfer (MLCT) in nature, contrasting previous findings for tricarbonyl complexes,
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Vibrational energy transfer (VET) between two isotopologues of [Re(dcb)(CO)Br] immobilized on a TiO surface is studied with the help of 2D IR spectroscopy in dependence of surface coverage. To dilute the molecules on the surface, and thereby control the intermolecular distances, two different diluents have been used: a third isotopologue of the same molecule and 4-cyanobenzoic acid. As expected, the VET rate decreases with dilution.

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The ground- and excited-state properties of six rhenium(I) κ-tricarbonyl complexes with 4'-(4-substituted-phenyl)terpyridine ligands bearing substituents of different electron-donating abilities were evaluated. Significant modulation of the electrochemical potentials and a nearly 4-fold variation of the triplet metal-to-ligand charge-transfer (MLCT) lifetimes were observed upon going from CN to OMe. With the more electron-donating NMe group, we observed in the κ complex the appearance of a very strong absorption band, red-shifted by ca.

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Cycloruthenation is a well known process in organometallic ruthenium chemistry. In this work, we report unprecedented cycloruthenated rhenium bis-arene compounds with planar chirality. In a two-step process, the reaction of acetyl-pyridine with [Re(η6-C6H6)2]+ introduced a pyridinyl-methanol ligand at one of the arene rings.

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Hydridocarbonyl complexes, a class of industrially relevant catalysts, contain both the M-H and M-CO moieties. Here, using two-dimensional infrared spectroscopy, we examine the coupling of the typically weak M-H stretching mode and the intense M(C≡O) mode. By studying a series of Ir(I)- and Ir(III)-based hydridocarbonyl complexes, we show that the arrangement of the H and CO ligands in a configuration leads to strong vibrational coupling and mode delocalization.

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Proton-coupled electron transfer (PCET) was studied in a series of tungsten hydride complexes with pendant pyridyl arms ([(PyCHCp)WH(CO)], PyCHCp = pyridylmethylcyclopentadienyl), triggered by laser flash-generated Ru--bipyridine oxidants, in acetonitrile solution. The free energy dependence of the rate constant and the kinetic isotope effects (KIEs) showed that the PCET mechanism could be switched between concerted and the two stepwise PCET mechanisms (electron-first or proton-first) in a predictable fashion. Straightforward and general guidelines for how the relative rates of the different mechanisms depend on oxidant and base are presented.

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The response of water re-solvating a charge-transfer dye (deprotonated Coumarin 343) after photoexcitation has been measured by means of transient THz spectroscopy. Two steps of increasing THz absorption are observed, a first ∼10 ps step on the time scale of Debye relaxation of bulk water and a much slower step on a 3.9 ns time scale, the latter of which reflecting heating of the bulk solution upon electronic relaxation of the dye molecules from the S back into the S state.

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Article Synopsis
  • The text discusses a new molecular triad designed to facilitate a rapid process called multiple-site concerted proton-electron transfer (MS-CPET), crucial for energy conversion and storage in systems like photosynthesis and fuel cells.
  • Experiments revealed that this MS-CPET occurs very quickly (around 3.2 × 10 seconds at room temperature) and remains consistent across a wide temperature range (5.5 to 350 K), with no significant activation energy required.
  • The findings suggest that the transfer of both protons and electrons happens via quantum tunneling, which explains the high efficiency and speed of the reaction without relying on thermal energy.
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A covalently linked organic dye-cobaloxime catalyst system based on mesoporous NiO is synthesized by a facile click reaction for mechanistic studies and application in a dye-sensitized solar fuel device. The system is systematically investigated by photoelectrochemical measurements, density functional theory, time-resolved fluorescence, transient absorption spectroscopy, and photoelectron spectroscopy. The results show that irradiation of the dye-catalyst on NiO leads to ultrafast hole injection into NiO from the excited dye, followed by a fast electron transfer process to reduce the catalyst.

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For the first time, organic semiconducting polymer dots (Pdots) based on poly[(9,9'-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3} thiadiazole)] (PFBT) and polystyrene grafting with carboxyl-group-functionalized ethylene oxide (PS-PEG-COOH) are introduced as a photocatalyst towards visible-light-driven hydrogen generation in a completely organic solvent-free system. With these organic Pdots as the photocatalyst, an impressive initial rate constant of 8.3 mmol h(-1)  g(-1) was obtained for visible-light-driven hydrogen production, which is 5-orders of magnitude higher than that of pristine PFBT polymer under the same catalytic conditions.

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