The cationic complex Pt(tolylterpyridine)(phenylacetylide)+ has been used as a photosensitizer for the reduction of aqueous protons in the presence of a sacrificial electron donor to make H2. In this ...system, triethanolamine (TEOA) acts as the sacrificial reducing agent, methyl viologen (MV2+) serves as an electron transfer agent, and colloidal Pt stabilized by polyacrylate functions as the catalyst for H2 generation. The Pt(II) chromophore undergoes both oxidative and reductive quenching, but H2 is only seen when both TEOA and MV2+ are present. Irradiation of the reaction solution for 10 h with λ > 410 nm leads to 85 turnovers and an overall yield of 34% based on TEOA. While H2 evolution is maximized for the system at pH 7, it is also seen at pH 5 and 9, in contrast with earlier reports using Ru(bpy)3 2+ as the photosensitizer. This is the first time that a Pt diimine or terpyridyl complex has been used as the photosensitizer for H2 generation from aqueous protons.
Electrolyte additives such as vinylene carbonate (VC) have been demonstrated to improve the capacity retention for many types of Li-ion battery electrodes, including intermetallic alloying anodes, ...but it is still unclear why VC extends the cycle lifetime of copper antimonide (Cu2Sb) anodes so dramatically. Here, we have studied how VC affects the solid electrolyte interface formed on Cu2Sb thin film anodes in fluorine-free electrolyte solutions in order to better understand which nonfluorinated species may play an important role in effective Cu2Sb passivation. Using differential capacity analysis and X-ray photoelectron spectroscopy, we have found that VC effectively passivates Cu2Sb and prevents Cu/Cu2Sb oxidation at high potentials. Carbonate species from the reduction of VC seem to play an important role in passivation, while inorganic species like LiClO4 from the F-free supporting electrolyte do not seem to be beneficial.
Surface analysis of air-sensitive samples is difficult without controlled-environment sample transfer tubes or expensive vacuum transfer suitcases. Through the use of vacuum sealing and commercial ...magnets, we demonstrate a concept for a sample holder that can be used to transfer samples from an inert environment directly into an X-ray photoelectron spectrometer. Our results show the efficacy of the holder through analysis of an air-sensitive CuCl powder, where oxidation was not observed when using the sample holder. This method offers a simple, low-cost alternative to enable routine air-free measurements in instrumentation with vacuum-controlled sample introduction chambers. Our aim with this report is to share the design so that this sample holder can be made anywhere where there is access to a basic machine shop.
Catastrophic losses (ca. 95%) of seagrass and increased environmental degradation have occurred during the past decade in the Indian River Lagoon (IRL) estuary on the US Atlantic coast of Florida. ...Changes were observed in the abundance of 2 closely related sparid fishes in these estuarine waters based on fishery-independent monitoring efforts over 22 yr: sea bream Archosargus rhomboidalis significantly increased, while sheepshead A. probatocephalus simultaneously declined. These abundance trends and a northward expansion of sea bream into areas where they had never been documented were associated with an annual minimum water temperature increase of approximately 1.5°C, an annual mean water temperature increase of 0.9°C, and an annual mean salinity increase of 7.6 ppt. Lost seagrass habitat was often replaced by species belonging to the attached macroalgae genus Caulerpa or remained bare. Our findings suggest that sea bream, a tropical herbivore, are expanding poleward into the northern IRL, which may further negatively impact the potential recovery of sheepshead populations via competition. Furthermore, observed declines in seagrasses and populations of dependent species, including sheepshead, will likely continue if anthropogenic perturbations persist or expand. Long-term monitoring is essential for the timely detection of population changes and range shifts to better refine direct fisheries management of existing species and determine the potential need for management of recently expanding fish species should new fisheries emerge. Effective monitoring also allows for more proactive restoration of critical habitats and water conditions to minimize further adverse effects on fishes and other estuarine biota.
The photochemistry and photophysics of the cationic molecular dyad, 5-{4-rhenium(I)tricarbonylpicoline-4-methyl-2,2′-bipyridine-4′-carboxyamidylphenyl}-10,15,20-triphenylporphyrinatopalladium(II) ...(Re(CO) 3 (Pic)Bpy-PdTPPPF6) have been investigated. The single crystal X-ray structure for the thiocyanate analogue, Re(CO) 3 (NCS)Bpy-PdTPP, exhibits torsion angles of 69.1(9)°, 178.1(7)°, and 156.8(9)° between porphyrin plane, porphyrin-linked C6H4 group, amide moiety, and Bpy, respectively. Steady-state photoexcitation (λex = 520 nm) of Re(CO) 3 (Pic)Bpy-PdTPPPF6 in dimethylformamide (DMF) results in substitution of Pic by bromide at the Re(I)Bpy core. When Re(CO) 3 (Pic)Bpy-PdTPPPF6 is employed as a photocatalyst for the reduction of CO2 to CO in DMF/NEt3 solution with λex > 420 nm, 2 turnovers (TNs) CO are formed after 4 h. If instead, a two-component mixture of PdTPP sensitizer and mononuclear Re(CO)3(Pic)BpyPF6 catalyst is used, 3 TNs CO are formed. In each experiment however, CO only forms after a slight induction period and during the concurrent photoreduction of the sensitizer to a Pd(II) chlorin species. Palladium(II) meso-tetraphenylchlorin, the hydrogenated porphyrin analogue of PdTPP, has been synthesized independently and can be substituted for PdTPP in the two-component system with Re(CO)3(Pic)BpyPF6, forming 9 TNs CO. An intramolecular electron transfer process for the dyad is supported by cyclic voltammetry and steady-state emission studies, from which the free energy change was calculated to be ΔG ox* = −0.08 eV. Electron transfer from Pd(II) porphyrin to Re(I) tricarbonyl bipyridine in Re(CO) 3 (Pic)Bpy-PdTPPPF6 was monitored using time-resolved infrared (TRIR) spectroscopy in the ν(CO) region on several time scales with excitation at 532 nm. Spectra were recorded in CH2Cl2 with and without NEt3. Picosecond TRIR spectroscopy shows rapid growth of bands assigned to the π–π* excited state (2029 cm–1) and to the charge-separated state (2008, 1908 cm–1); these bands decay and the parent recovers with lifetimes of 20–50 ps. Spectra recorded on longer time scales (ns, μs, and seconds) show the growth and decay of further species with ν(CO) bands indicative of electron transfer to Re(Bpy).
A novel terpyridine ligand containing a pentaphenylphenyl moiety linked to the terpyridyl core (1-terpyridyl-2,3,4,5,6-pentaphenyl-benzene (TPPPB)) has been synthesized in good yield and reacted with ...Pt(DMSO)2Cl2, to produce the cationic complex Pt(TPPPB)ClCl (5). 5 was studied structurally and spectroscopically. It is observed to be brightly luminescent in the solid state at room temperature and at 77 K, with no change in λem max. The complex exhibits reversible vapochromic behavior upon exposure to methylene chloride vapors, changing color from red (5-R) to green (5-G). The shift to higher energy in the emission maximum from 654 to 514 nm is the largest vapochromic shift (140 nm) yet reported. The Pt(TPPPB)ClCl complex exhibits high selectivity for certain volatile organic compounds (VOCs) including methylene chloride, ethanol, ethyl acetate, and acetonitrile. The crystal structures of both the green and red forms have been determined by single-crystal X-ray diffraction. In both forms, the cationic Pt(II) complex possesses the anticipated square-planar coordination geometry that is distorted as a consequence of constraints from the terpyridyl binding. Analysis of the crystal packing of the green form (5-G) reveals the presence of non-interacting Pt···Pt separations with distances of 3.9092(9) and 4.5483(11) Å and a zigzag arrangement between neighboring Pt(II) ions. The red form (5-R) contains complexes that are stacked with Pt···Pt separations of 3.2981(14) and 3.3427(14) Å, indicative of metallophilic interaction. The change in the emitting state, as a consequence of the effect of the volatile organic compounds, results from a disruption of the d8−d8 metallophilic interactions in the red form and its metal−metal-to-ligand charge transfer (MMLCT) excited state to a more-localized Pt(dπ)-to-tpy(π*) metal-to-ligand charge transfer (MLCT) excited state in the green form.
The properties of amorphous calcium carbonate (ACC) and its transformations to crystalline polymorphs are frequently studied in aqueous systems and in small quantities. In this study, synthetic ...calcium carbonate stones are created from bulk ACC and crystalline polymorphs, which were precipitated from gaseous CO 2 , at a gradient of end pH. Some of the ACCs hardened into stones which are durable against an abrasion and impact test, while some of the ACCs create fragile, friable stones. When ACCs which transform to durable stones and those which transform into fragile stones were subject to calorimetry, significant differences were observed. These stones, synthesized from gaseous CO 2 , can be used as a storage reservoir for utilized CO 2 in construction and other infrastructure applications.
The structural and photophysical properties of a new series of cationic and neutral Au(I) dinuclear compounds (1 and 2, respectively) bridged by bis(diphenylphosphino)methane (dppm) and substituted ...benzimidazolethiolate (X−BIT) ligands, where X = H (a), Me (b), OMe (c), and Cl (d), have been studied. Monocationic complexes, Au2(μ-X−BIT)(μ-dppm)(CF3CO2), were prepared by the reaction of Au2(μ-dppm)(CF3CO2)2 with 1 equiv of X−BIT in excellent yields. The cations 1a−1d possess similar molecular structures, each with a linear coordination geometry around the Au(I) nuclei, as well as relatively short intramolecular Au(I)···Au(I) separations ranging between 2.88907(6) Å for 1d and 2.90607(16) Å for 1a indicative of strong aurophilic interactions. The cations are violet luminescent in CH2Cl2 solution with a λem max of ca. 365 nm, assigned as ligand-based or metal-centered (MC) transitions. Three of the cationic complexes, 1a, 1b, and 1d, exhibit unusual luminescence tribochromism in the solid-state, in which the photoemission is shifted significantly to higher energy upon gentle grinding of microcrystalline samples with ΔE = 1130 cm-1 for 1a, 670 cm-1 (1b), and 870 cm-1 (1d). The neutral dinuclear complexes, Au2(μ-X−BIT)(μ-dppm) (2a−2d) were formed in good yields by the treatment of a CH2Cl2 solution of cationic compounds (1) with NEt3. 2a−2d aggregate to form dimers having substantial intra- and intermolecular aurophilic interactions with unsupported Au(I)···Au(I) intermolecular distances in the range of 2.8793(4)−2.9822(8) Å, compared with intramolecular bridge-supported separations of 2.8597(3)−2.9162(3) Å. 2a-2d exhibit brilliant luminescence in the solid-state and in DMSO solution with red-shifted λem max energies in the range of 485−545 nm that are dependent on X−BIT and assigned as ligand-to-metal−metal charge transfer (LMMCT) states based in part on the extended Au···Au···Au···Au interactions.
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