Tuning PtII-Based Donor–Acceptor Systems through Ligand Design: Effects on Frontier Orbitals,Redox Potentials,UV/Vis/NIR Absorptions,Electrochromism, and Photocatalysis

Asymmetric platinum donor–acceptor complexes [(pimp)Pt(Q²⁻)] are presented in this work, in which pimp=[(2,4,6-trimethylphenylimino)methyl]pyridine and Q²⁻=catecholate-type donor ligands. The properties of the complexes are evaluated as a function of the donor ligands, and correlations are drawn among electrochemical, optical, and theoretical data. Special focus has been put on the spectroelectrochemical investigation of the complexes featuring sulfonyl-substituted phenylendiamide ligands, which show redox-induced linkage isomerism upon oxidation. Time-dependent density functional theory (TD-DFT) as well as electron flux density analysis have been employed to rationalize the optical spectra of the complexes and their reactivity. Compound 1 ([(pimp)Pt(Q²⁻)] with Q²⁻=3,5-di-tert-butylcatecholate) was shown to be an efficient photosensitizer for molecular oxygen and was subsequently employed in photochemical cross-dehydrogenative coupling (CDC) reactions. The results thus display new avenues for donor–acceptor systems, including their role as photocatalysts for organic transformations, and the possibility to introduce redox-induced linkage isomerism in these compounds through the use of sulfonamide substituents on the donor ligands.     

Application of pulsed-magnetic field enhances non-viral gene delivery in primary cells from different origins

Primary cell lines are more difficult to transfect when compared to immortalized/transformed cell lines, and hence new techniques are required to enhance the transfection efficiency in these cells. We isolated and established primary cultures of synoviocytes, chondrocytes, osteoblasts, melanocytes, macrophages, lung fibroblasts, and embryonic fibroblasts. These cells differed in several properties, and hence were a good representative sample of cells that would be targeted for expression and delivery of therapeutic genes in vivo. The efficiency of gene delivery in all these cells was enhanced using polyethylenimine-coated polyMAG magnetic nanoparticles, and the rates (17–84.2%) surpassed those previously achieved using other methods, especially in cells that are difficult to transfect. The application of permanent and pulsating magnetic fields significantly enhanced the transfection efficiencies in synoviocytes, chondrocytes, osteoblasts, melanocytes and lung fibroblasts, within 5 min of exposure to these magnetic fields. This is an added advantage for future in vivo applications, where rapid gene delivery is required before systemic clearance or filtration of the gene vectors occurs.     

Modeling investment behavior under price cap regulation

Motivated by the frequently observed criticism of the regulatory practice arising from companies in the industries concerned, we investigate the impact of regulation on investment behavior. Therefore, we model the investment timing and volume of a firm acting in a regulated market. When capping prices, the regulatory authority imposes a price ceiling on market prices. Accordingly, we use a real option approach where the price cap that limits possible future firm values enters the firm’s portfolio in form of a short call option position. By comparing this framework to a competitive benchmark model, we derive an optimal price setting rule for regulators. Moreover, it can be shown how deviations from this optimum affect the investment behavior of firms.      

Photochemistry of Methane on Pd/Al2O3 Model Catalysts: Control of Photochemistry on Transition Metal Surfaces

The mean size of the Pd clusters deposited on an Al₂O₃ thin film influences the efficiency of photodissociation of CD₄ into CD₃ and D as well as the photodesorpion upon irradiation with 193-nm laser light. The picture shows the degree of desorption on Pd clusters of various sizes (as well as on a Pd(111) single-crystal surface) as a function of temperature; the values given refer to the average thickness of the evaporated metal layer.     

A Dicobalt Complex with an Unsymmetrical Quinonoid Bridge Isolated in Three Units of Charge: A Combined Structural, (Spectro)electrochemical,Magnetic and Spectroscopic Study

Quinonoid ligands are excellent bridges for generating redox‐rich dinuclear assemblies. A large majority of these bridges are symmetrically substituted, with examples of unsymmetrically substituted quinonoid bridges being extremely rare. We present here a dicobalt complex in its various redox states with an unsymmetrically substituted quinonoid bridging ligand. Two homovalent forms and one mixed‐valent form have been isolated and characterized by single crystal X‐ray diffraction. The complex displays a large comproportionation constant for the mixed‐valent state which is three orders of magnitude higher than that observed for the analogous complex with a symmetrically substituted bridge. Results from electrochemistry, UV/Vis/NIR spectroelectrochemistry, SQUID magnetometry, multi‐frequency EPR spectroscopy and FIR spectroscopy are used to probe the electronic structures of these complexes. FIR provides direct evidence of exchange coupling. The results presented here display the advantages of using an unsymmetrically substituted bridge: site specific redox chemistry, high thermodynamic stabilization of the mixed‐valent form, isolation and crystallization of various redox forms of the complex. This work represents an important step on the way to generating heterodinuclear complexes for use in cooperative catalysis.     

Tailoring RuII Pyridine/Triazole Oxygenation Catalysts and Using Photoreactivity to Probe their Electronic Properties

Tuning of ligand properties is at the heart of influencing chemical reactivity and generating tailor‐made catalysts. Herein, three series of complexes [Ru(L)(Cl)(X)]PF₆ (X=DMSO, PPh₃, or CD₃CN) with tripodal ligands (L1–L5) containing pyridine and triazole arms are presented. Triazole‐for‐pyridine substitution and the substituent at the triazole systematically influence the redox behavior and photoreactivity of the complexes. The mechanism of the light‐driven ligand exchange of the DMSO complexes in CD₃CN could be elucidated, and two seven‐coordinate intermediates were identified. Finally, tuning of the ligand framework was applied to the catalytic oxygenation of alkanes, for which the DMSO complexes were the best catalysts and the yield improved with increasing number of triazole arms. These results thus show how click‐derived ligands can be tuned on demand for catalytic processes.     

Electrocatalytic Dihydrogen Production with a Robust Mesoionic Pyridylcarbene Cobalt Catalyst

A Co^III complex with a mesoionic pyridylcarbene ligand is presented. This complex is an efficient electrocatalyst for H₂ production at very low overpotential and high turnovers when using a (glassy carbon) GC electrode. The corresponding triazole complexes display no catalytic activity whatsoever under identical conditions. The remarkable robustness of the Co? C(carbene) bond towards acids is likely responsible for the high efficiency of this catalyst. The present results thus open new avenues for carbene‐based ligands for generating functional models for hydrogenases.