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Stable Singlet Biradicals of Rare-Earth-Fused Diporphyrin-Triple-Decker Complexes Having Low Energy Gaps and Multi-Redox States
摘要： Dinuclear rare-earth (TbIII, YIII) triple-decker complexes with a fused-diporphyrin (FP) and two tetraphenylporphyrin (TPP) ligands were synthesized in neutral, dianionic, and diprotonated forms. The neutral forms have large open shell biradical character, as determined from the temperature dependency of the magnetic susceptibility measurements and theoretical calculations. The coupling value (J = ?1.4 kcal mol?1, ?487 cm?1) of the radical centers in the neutral form of the YIII complex indicates weak pairing interactions. Theoretical calculations on the neutral form reveal a significant biradical character (y = 68%). Furthermore, the TbIII complex exhibits multi-redox states, having more than eight clear peaks in the voltammetry curves. The optical (3700 nm, 0.33 eV) and electrochemical measurements (3400 nm, 0.36 eV) indicate that the neutral form has very small HOMO?LUMO energy gap. Despite the large biradical character, the neutral complexes are thermally stable and do not decompose on heating at 120 ?C. These complexes with unique characteristics are promising candidates for use in molecular electronics, optics, and spintronics.
关键词： rare earths,redox chemistry,radicals,sandwich complexes,porphyrinoids
更新于2025-09-23 15:22:29
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Redox-Switchable Cyan Fluorescence of a BODIPY Analog Inspired by Propentdyopent Pigments
摘要： The combination of reversible redox chemistry and bright redox-responsive emission properties is key to the development of electrofluorochromic switches for applications in bioimaging and optoelectronics. Herein, the redox-active dipyrrin-1,9-dione fragment, which is characteristic of the propentdyopent family of heme metabolites and urinary pigments, is employed for the synthesis of a BODIPY analog. This boron difluoride complex exhibits bright fluorescence in organic solvents and a significant ipsochromic shift to the cyan region when compared to typical green BODIPY dyes. Electrochemical and spectroscopic measurements show that the dipyrrindione ligand acts as an electron reservoir by hosting an unpaired spin upon one-electron reduction. This ligand-based redox event reversibly abolishes the fluorescence emission, thus switching off the novel electrofluorochromic system.
关键词： Redox chemistry,Switches,BODIPY,Fluorescence,Dyes/Pigments
更新于2025-09-23 15:21:01
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When Does Organic Photoredox Catalysis Meet Artificial Photosynthesis?
摘要： The basics of photocatalysis are under investigation for more than a century. Contemporary science maintains an emphasis on fundamental studies, but application-oriented research in solar energy conversion, environmental remediation, light-promoted chemical synthesis and medicinal phototherapy is growing rapidly. These prospects have triggered a renaissance of the field and breath-taking progress has been made in the last decade by chemists from all major branches. Artificial photosynthesis aims to produce a renewable fuel using sunlight. This 'solar fuel' is thereby synthesized from the reduction of water or carbon dioxide, coupled to the oxidation of a substrate; typically, water to O2. The underlying endothermic multi-electron/multi-proton chemistry is relatively well understood, but the assembly of a commercially viable device remains elusive due to the 'low' market-value of chemical fuels. Photoreforming can decompose organics such as waste biomass (lignocellulose), plastics or pollutants to produce a fuel using solar irradiation. This process has overall a much-reduced thermodynamic barrier compared to overall water splitting, but suffers from a kinetically challenging reaction, insufficient solubility of polymeric substrate or low concentration of pollutants. Organic photoredox catalysis uses light to accelerate chemical reactions by well-controlled single-electron redox events. This radical chemistry approach has not only allowed for improved synthetic procedures, but also new transformations to proceed. The value-added organic products are synthesized in controlled laboratory environments, usually using LED lamps. Although photocatalysis is of growing interest to the chemical and pharmaceutical industry, large-scale processes have rarely been implemented. Medicinal chemistry develops light sensitive medication for the destruction of abnormal cells. In photodynamic therapy, the photosensitizer drug is irradiated using a defined wavelength and reacts with O2 to produce reactive oxygen species to exert phototoxicity. Achieving high quantum yields and the development of red (or near IR) light absorbers (for improved skin penetration) are common objectives with artificial photosynthesis (for optimal solar light harvesting). Although the same basics of photochemistry unite these applications, they are being developed in surprising isolation as inorganic and physical chemists focus on artificial photosynthesis, chemical engineers on photoreformation, organic chemists on photoredox catalysis, and medicinal chemists on photodynamic therapy. This divide is cemented by separating the scientists often in different institutes, teaching structures and firmly placing them in separate academic communities. This editorial is intended as a call to join forces and embrace progress in all of these areas to enable accelerated development of a more holistic science in photocatalysis. There is plenty we can learn from each other as we share mutual interests and common goals. The quickly developing pool of environmentally benign, robust, non-toxic, scalable and efficient photocatalysts for solar fuel synthesis provides vast opportunities for improved and new organic catalysis. For example, heterogeneous photocatalysts such as semiconductor powders and photoelectrochemical architectures are rarely employed in organic chemistry. Time-resolved spectroscopy can provide in-depth understanding of electron transfer dynamics and insights into organic mechanisms. Proton-coupled multi-electron and endothermic photochemistry may pave the way to currently inaccessible organic chemistry. Coupling of solar fuel synthesis to value added oxidation chemistry for bulk or even fine chemical synthesis is a largely untapped territory (Figure 1). The simultaneous production of a chemical fuel and value-added organic improves the economics in artificial photosynthesis and may accelerate market penetration for solar fuels. Understanding organic transformations and industrial processes allows the selection of meaningful alternatives to water oxidation. Clean organic oxidations with high selectivity and conversion yield are key criteria to distinguish them from the use of undesirable sacrificial electron donors. It may be true that we cannot produce enough fuel to power the planet by coupling fuel synthesis to organic chemistry, but it is nevertheless an attractive entry point for commercialisation as well as a rich intellectual playground for academic research. Photoreforming can be exploited for simultaneous fuel production and chemical synthesis from an organic waste substrate, thereby addressing the issues of renewable energy generation and sustainable chemical synthesis with environmental remediation. Agricultural and plastic waste are a valuable resource that should not go to landfills. It contains stored energy and useful chemical building blocks for chemical transformations. Photoreformation of lignocellulose and plastics has been demonstrated to provide access to clean H2 fuel as well as organic chemicals. A final question concerns the use of sunlight versus electrical (LED) irradiation and this will ultimately depend on the application. The common view is that the synthesis of organics will be performed in the laboratory using LEDs, whereas fuel production requires large land-areas and therefore sunlight. But there are plenty of alternative possibilities and scenarios to challenge this traditional view. Could the drop in renewable (solar) electricity production may ultimately make fuel synthesis with efficient LEDs possible? Why not consider swimming-pool sized flow-reactors powered by the sun for bulk chemical production or solar-concentrators for greener organic synthesis? Solar-driven chemistry can also give access to off-grid synthesis of fertilisers, medicine, and commodities in remote areas and sun-rich developing countries. Some of these suggestions may indeed appear naive, but cross-fertilisation and an open mind will ultimately provide the basis for new developments in photocatalysis.
关键词： photocatalysis,photosynthesis,organocatalysis,solar fuels,redox chemistry
更新于2025-09-19 17:15:36
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Hexaarylbutadiene: a versatile scaffold with tunable redox properties towards organic neara??infrared electrochromic material
摘要： When 1,1,4,4-tetraanilinobutadiene skeleton is attached with two halogenated aryl units at 2,3-position, they undergo facile two-electron oxidation to give stable dicationic dyes which exhibit a near-infrared (NIR) absorption whereas the neutral dienes show only pale color. Therefore, a distinct electrochromic response with an absorption change in the NIR region is achieved, which are attracting considerable recent attention from the viewpoint of bioimaging. Herein, we demonstrate that the redox potentials of the 1,1,4,4-tetraanilinobutadiene can be precisely controlled by the donating properties of the amino group on the aniline unit as well as the number of halogen atoms on the aryl units at 2,3-positions on the butadiene. In contrast, the NIR absorption bands mainly depend on the number of halogen atoms irrespective to the donating properties of aniline unit. Thus, the hexaarylbutadiene skeleton is proven to be a versatile scaffold to develop less-explored organic electrochromic materials, whose redox and spectroscopic properties can be finely tuned by modifying/attaching the proper substituents.
关键词： Redox chemistry,Absorption,Cations,Cyclic voltammetry
更新于2025-09-19 17:13:59
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Single Crystal Growth and Characterization of the Chalcopyrite Semiconductor CuInTe2 for Photoelectrochemical Solar Fuel Production
摘要： Transition metal chalcogenides are a promising family of materials for applications as photocathodes in photoelectrochemical (PEC) H2 generation. A long-standing challenge for chalcopyrite semiconductors is characterizing their electronic structure—both experimentally and theoretically—due to their relatively high energy bandgaps and spin orbit coupling (SOC), respectively. In this work, we present single crystals of CuInTe2, whose relatively small optically measured bandgap of 0.9 ± 0.03 eV enables electronic structure characterization by angle-resolved photoelectron spectroscopy (ARPES) in conjunction with first-principle calculations incorporating SOC. ARPES measurements reveal bands that are steeply dispersed in energy with a band velocity of 2.5-5.4 x 105 m/s, almost 50% of the extremely conductive material graphene. Additionally, CuInTe2 single crystals are fabricated into electrodes to experimentally determine the valence band edge energy and confirm the thermodynamic suitability of CuInTe2 for water redox chemistry. The electronic structure characterization and band edge position presented in this work provide kinetic and thermodynamic factors that support CuInTe2 as a strong candidate for water reduction.
关键词： photoelectrochemical H2 generation,electronic structure,spin orbit coupling,chalcopyrite semiconductors,band velocity,valence band edge energy,Transition metal chalcogenides,angle-resolved photoelectron spectroscopy,water redox chemistry,CuInTe2
更新于2025-09-10 09:29:36
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Multi-electron reduction of Wells–Dawson polyoxometalate films onto metallic, semiconducting and dielectric substrates
摘要： The investigation of conditions allowing multi-electron reduction and reoxidation of polyoxometalate (POM) films onto solid substrates is considered an issue of critical importance for their successful incorporation in electronic devices, different types of sensors and catalytic systems. In the present paper, the rich multi-electron redox chemistry of films of Wells–Dawson ammonium salts, namely (NH4)6P2Mo18O62 and (NH4)6P2W18O62, on top of metallic (Al), semiconducting (ITO) and dielectric (SiO2) substrates under ambient conditions is investigated. The respective Keggin heteropolyacids, H3PMo12O40 and H3PW12O40, are also investigated for comparison. On Al substrates, the Wells–Dawson ammonium salts are found to be significantly more reduced (4–6e?) compared to the respective Keggin heteropolyacids (≤2e?), in accordance with their deeper lying lowest unoccupied molecular orbital (LUMO) level. Subsequent thermal treatment in air results in reoxidation of the initially highly reduced POM films. Similar behavior is found on ITO substrates, but in initially less reduced (2–4e?) Wells–Dawson POM films. On the other hand, on SiO2 substrates, the thermal reduction of (NH4)6P2Mo18O62 film is observed and attributed to the thermal oxidation of ammonium counterions by [P2Mo18O62]6? anions. Overall, the multi-electron reduction of Wells–Dawson ammonium salts onto metallic and semiconducting substrates (Al, ITO) is determined by the relative position of the LUMO level of POMs in relation to the Fermi level of the substrate (i.e. substrate work function) and affected in a synergistic way by the presence of ammonium counterions. In contrast, on dielectric substrates (SiO2) the reduction of Wells–Dawson POMs ((NH4)6P2Mo18O62) is attributed only to the oxidation of ammonium counterions.
关键词： Polyoxometalates,Semiconducting substrates,Ammonium counterions,Wells–Dawson ammonium salts,Redox chemistry,Keggin heteropolyacids,Metallic substrates,Dielectric substrates,Thermal treatment,Multi-electron reduction
更新于2025-09-04 15:30:14