ABSTRACT
The photoswitching and competitive processes of two photochromic dithienylethenes (DTEs) functionalized at both sides with 2-ureido-4[1H]-pyrimidone (UPy) quadruple hydrogen-bonding recognition patterns have been investigated with NMR experiments, ultrafast spectroscopy, and density functional theory (DFT) calculations. The originality of these molecules is their ability to form large supramolecular assemblies induced by light for the closed form (CF) species while the open form (OF) species exist as small oligomers. Photochromic parameters have been determined and photochemical pathways have been rationalized with clear distinction between the antiparallel (OF-AP) and parallel (OF-P) species. A new photocyclization pathway via triplet manifold has been evidenced. The effect of the supramolecular assembly on the photochemical response is discussed. Unlike the photoreversion process, which is unaffected by supramolecular assembly, rate constants of the photocyclization reaction and intersystem crossing process are sensitive to the presence of small OF oligomers.
ABSTRACT
The straightforward synthesis of a new Cu(i) metal-rich small metallacycle is presented. This compound is luminescent in the solid state with an emission quantum yield of 72% at room temperature and displays a pronounced reversible red-shift of its emission spectra upon cooling. Quantum chemical calculations reveal that these properties are governed by important geometrical relaxations that imply the formation of cuprophilic interactions at the excited states.
ABSTRACT
This study presents a pedagogical work carried out with a group of 13 school nurses of the Academy of Rennes, as part of a course in survey methodology. A descriptive survey aiming to achieve a better understanding of experienced health status of nurses, and of its repercussions on the execution of their missions, was implemented during the course, as a result of the demand and the expertise of the participants. Overall, nurses report to be in good health. However, one can not underestimate the existence of a group at risk (5% of the sample) that often suffers somatic troubles accompanied by sleep disorders and anxiety, as these risks concern primarily permanent staff nurses working in boarding establishments, with half of them falling into this category. A demand for regular monitoring of their health was clearly expressed through the study. This may be the object of a subsequent study by an academic team.