A photocatalytic water-reducing system utilizing a bis-cyclometalated bipyridyl iridium(III) photosensitizer (PS) and a platinum or palladium heterogeneous catalyst was used to identify systematic property-activity correlations among a library of structural derivatives of [Ir(ppy)(2)(bpy)](+). A heterogeneous Pd catalyst proved to be more durable than its previously reported Pt-based counterpart, allowing for more reliable photosensitizer study. The deliberate steric and electronic variations of the ppy and bpy moieties resulted in a dramatic decrease of the degradation rates observed with selected photosensitizers when compared to the more substitution-labile [Ir(ppy)(2)(bpy)](+) parent compound. An improved photosensitizer structure with a Pd catalyst in a nonligating solvent exhibited a 150-fold increase in catalyst turnover numbers compared to the system using [Ir(ppy)(2)(bpy)](+) and a Pt catalyst. Furthermore, photocatalytic and photophysical studies at varied temperatures provided information on the rate-limiting step of the photocatalytic process, which is shown to be dependent on both the PS and the Pt or Pd catalytic species.
Cyanogels are coordination polymers made from the reaction of a chlorometalate and a cyanometalate in aqueous solution, which undergo a sol-gel transition to form stable gels. At temperatures above 240 degrees C, the cyanide ligand acts as a reducing agent and reduces the metal centers to lower oxidation states. To understand the mechanism of the autoreduction, the thermal reduction of the Pd-Co cyanogel system formed by the reaction of PdCl4(2-) and Co(CN)6(3-) was studied in an inert atmosphere. It was found that the reduction proceeds through two polymeric cyanide-containing intermediates, CoPd(CN)4 and Pd(CN)2, that form upon reduction of Co(3+) to Co(2+) and involves a significant rearrangement of the coordination structure. The two intermediates upon further heating reduce to metallic products, which by solid-state diffusion form a single Pd/Co alloy product. CoPd(CN)4 was found to have a hydrated form Co(H2O)2Pd(CN)4 x 4 H2O with a layered structure crystallizing in an orthorhombic Pnma space group. The Pt-Co cyanogel was found to autoreduce via a similar route. CoPt(CN)4 was confirmed as an intermediate. Understanding of the mechanism of the cyanogel autoreduction is an important step toward better understanding of opportunities that cyanogels offer in materials chemistry, as well as an expansion of the knowledge of coordination chemistry at elevated temperatures in general.
Cyanogel coordination polymers are amorphous Prussian blue analogues formed in a hydrogel state by the reaction of a chlorometalate with a cyanometalate in aqueous solution. At elevated temperatures, cyanogels thermally autoreduce to form transition-metal alloys. This work demonstrates the general nature of this type of sol-gel processing chemistry to prepare binary and ternary transition-metal alloys (Pd/Co, Pt/Co, Ru/Co, Ir/Co, Pd/Ni, Pt/Ni, Pt/Ru, Pd/Fe, Pd/Fe/Co) and intermetallics (Pt 3 Fe, Pt 3 Co, PtCo). Tuning of the composition of the gels and alloys by a variety of methods is demonstrated. The thermal autoreduction can be induced either by convective heating or by microwave irradiation, as microwave dielectric heating of cyanogels leads to a sufficient temperature increase in the sample to cause the reduction of the metal centers.
The intramural the National Cancer Institute (NCI) and more recently the University of Texas Southwestern Medical Center with many different collaborators comprised a complex, multi‐disciplinary team that collaborated to generated large, comprehensively annotated, cell‐line related research resources which includes associated clinical, and molecular characterization data. This material has been shared in an anonymized fashion to accelerate progress in overcoming lung cancer, the leading cause of cancer death across the world. However, this cell line collection also includes a range of other cancers derived from patient‐donated specimens that have been remarkably valuable for other types of cancer and disease research. A comprehensive analysis conducted by the NCI Center for Research Strategy of the 278 cell lines reported in the original Journal of Cellular Biochemistry Supplement, documents that these cell lines and related products have since been used in more than 14 000 grants, and 33 207 published scientific reports. This has resulted in over 1.2 million citations using at least one cell line. Many publications involve the use of more than one cell line, to understand the value of the resource collectively rather than individually; this method has resulted in 2.9 million citations. In addition, these cell lines have been linked to 422 clinical trials and cited by 4700 patents through publications. For lung cancer alone, the cell lines have been used in the research cited in the development of over 70 National Comprehensive Cancer Network clinical guidelines. Finally, it must be underscored again, that patient altruism enabled the availability of this invaluable research resource.
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