7 research outputs found
Pyrimidoquinazolinophenanthroline Opens Next Chapter in Design of Bridging Ligands for Artificial Photosynthesis **
The synthesis and detailed characterization of a new Ru polypyridine complex containing a heteroditopic bridging ligand with previously unexplored metalâmetal distances is presented. Due to the twisted geometry of the novel ligand, the resultant division of the ligand in two distinct subunits leads to steady state as well as excited state properties of the corresponding mononuclear Ru(II) polypyridine complex resembling those of prototype [Ru(bpy) 3 ] 2+ (bpy=2,2'âbipyridine). The localization of the initially optically excited and the nature of the longâlived excited states on the Ruâfacing ligand spheres is evaluated by resonance Raman and fsâTA spectroscopy, respectively, and supported by DFT and TDDFT calculations. Coordination of a second metal (Zn or Rh) to the available bisâpyrimidylâlike coordination sphere strongly influences the frontier orbitals, apparent by, for example, luminescence quenching. Thus, the new bridging ligand motif offers electronic properties, which can be adjusted by the nature of the second metal center. Using the heterodinuclear RuâRh complex, visible lightâdriven reduction of NAD + to NADH was achieved, highlighting the potential of this system for photocatalytic applications
Cobaloxime complex salts : synthesis, patterning on carbon nanomembranes and heterogeneous hydrogen evolution studies
Cobaloximes are promising, earth-abundant catalysts for the light-driven hydrogen evolution reaction. Typically, these cobalt(III) complexes are prepared in situ or employed in their neutral form, e.g. [Co(dmgH 2 )(py)Cl], even though related complex salts have been reported previously and could in principle offer improved catalytic activity as well as more efficient immobilization on solid support. Here we report an interdisciplinary investigation into complex salts [Co(dmgH) 2 (py) 2 ] + [Co(dmgBPh 2 ) 2 Cl 2 ] - , TBA + [Co(dmgBPh 2 ) 2 Cl 2 ] - and [Co(dmgH) 2 (py) 2 ] + BArF - . We describe their strategic syntheses from commercially available complex [Co(dmgH) 2 (py)Cl] and demonstrate that these double and single complex salts are potent catalysts for the light-driven hydrogen evolution reaction. We also show that scanning electrochemical cell microscopy can be used to deposit arrays of catalysts [Co(dmgH) 2 (py) 2 ] + [Co(dmgBPh 2 ) 2 Cl 2 ] - and [Co(dmgH) 2 (py)Cl] on supported and free-standing amino-terminated ~ 1 nm thick carbon nanomembranes (CNMs). Photocatalytic H 2 evolution at such arrays was quantified with Pd microsensors using scanning electrochemical microscopy, thus providing a new approach for catalytic evaluation and opening up novel routes for the creation and analysis of âdesigner catalyst arraysâ, nano-printed in a desired pattern on a solid support
Combined mRNA expression levels of members of the urokinase plasminogen activator (uPA) system correlate with disease-associated survival of soft-tissue sarcoma patients
<p>Abstract</p> <p>Background</p> <p>Members of the urokinase-type plasminogen activator (uPA) system are up-regulated in various solid malignant tumors. High antigen levels of uPA, its inhibitor PAI-1 and its receptor uPAR have recently been shown to be associated with poor prognosis in soft-tissue sarcoma (STS) patients. However, the mRNA expression of uPA system components has not yet been comprehensively investigated in STS patients.</p> <p>Methods</p> <p>The mRNA expression level of uPA, PAI-1, uPAR and an uPAR splice variant, uPAR-del4/5, was analyzed in tumor tissue from 78 STS patients by quantitative PCR.</p> <p>Results</p> <p>Elevated mRNA expression levels of PAI-1 and uPAR-del4/5 were significantly associated with clinical parameters such as histological subtype (<it>P </it>= 0.037 and <it>P </it>< 0.001, respectively) and higher tumor grade (<it>P </it>= 0.017 and <it>P </it>= 0.003, respectively). In addition, high uPAR-del4/5 mRNA values were significantly related to higher tumor stage of STS patients (<it>P </it>= 0.031). On the other hand, mRNA expression of uPA system components was not significantly associated with patients' survival. However, in STS patients with complete tumor resection (R0), high PAI-1 and uPAR-del4/5 mRNA levels were associated with a distinctly increased risk of tumor-related death (RR = 6.55, <it>P </it>= 0.054 and RR = 6.00, <it>P </it>= 0.088, respectively). Strikingly, R0 patients with both high PAI-1 and uPAR-del4/5 mRNA expression levels showed a significant, 19-fold increased risk of tumor-related death (<it>P </it>= 0.044) compared to the low expression group.</p> <p>Conclusion</p> <p>Our results suggest that PAI-1 and uPAR-del4/5 mRNA levels may add prognostic information in STS patients with R0 status and distinguish a subgroup of R0 patients with low PAI-1 and/or low uPAR-del4/5 values who have a better outcome compared to patients with high marker levels.</p
Umwandlung von Escherichia coli Proteomembranen in artifizielle Chloroplasten durch molekulare Photokatalyse
Molecular Scylla and Charybdis: Maneuvering between pH Sensitivity and Excited-State Localization in Ruthenium Bi(benz)imidazole Complexes
Insights into the different mechanistic stages of light-induced hydrogen evolution of a 5,5âČ-bisphenanthroline linked RuPt complex
Herein, the synthesis in conjunction with the structural, electrochemical, and photophysical characterization of a 5,5'-bisphenanthroline (phenphen) linked heterodinuclear RuPt complex (Ru(phenphen)Pt) and its light-driven hydrogen formation activity are reported. A single crystal X-ray diffraction (SC-XRD) analysis identified a perpendicular orientation of the two directly linked 1,10-phenanthroline moieties. The disruption of pi-conjugation blocks intramolecular electron transfer as evidenced by a comparative time-resolved optical spectroscopy study of Ru(phenphen)Pt and the reference complexes Ru(phenphen) and Ru(phenphen)Ru. However, reductive quenching is observed in the presence of an external electron donor such as triethylamine. Irradiating Ru(phenphen)Pt with visible light (470 nm) leads to H-2 formation. We discuss a potential mechanism that mainly proceeds via Pt colloids and provide indications that initial hydrogen generation may also proceed via a molecular pathway. As previous reports on related heterodinuclear RuPt-based photocatalysts revealed purely molecular hydrogen evolution, the present work thus highlights the role of the bridging ligand in stabilizing the catalytic center and consequently determining the mechanism of light-induced hydrogen evolution in these systems
Polydopamine coated CdSe@CdS dot-in-rod heterostructures with Rhodium-based catalysts for stable photocatalytic NAD+ reduction
We report on a photocatalytic system consisting of CdSe@CdS nanorods, coated with a polydopamine (PDA) shell functionalized with molecular rhodium catalysts. The PDA shell was implemented to enhance photostability of the photosensitizer, to improve charge carrier separation and to offer multiple options for stable covalent functionalization, allowing for spatial proximity and efficient shuttling of charges between sensitizer and reaction center. The activity of the photocatalytic system was demonstrated by light-driven reduction of nicotinamide adenine dinucleotide (NAD+) to its reduced form NADH. This work shows that PDA coated nanostructures present an attractive platform for covalent attachment of reduction and oxidation reaction centers for photocatalytic applications