With the aim of obtaining efficient near infra-red emitters, a family of ruthenium and polyruthenium complexes made from tetrapyridyl analogs and terpyridine ligands was synthesized. It was expected that the increase in size of the complex would result in the progressive shift of the absorption and emission spectra towards the infra red and above all that the stability and rigidity of these complexes would be associated to a high emission yield. If the expected shifts are obtained, with emission at 820 nm for a bisruthenium complex for instance, quantum yields are very low, usually between 10-2 and 10-3. More disturbing, these compounds display an `anormalous emission' at shorter wavelength. The latter does not appear to be due to impurities since it is different for all these molecules which are built from the same precursors treated in similar conditions. Preliminary studies point to the fact that the bite angles of the multidentate ligands are not adapted to the binding to ruthenium and that this mismatch gives rise to a tension which can be released only by having a ligand pop off one binding position. The resulting species is distorted, with a reduced conjugation or electronic communication between the metal centers, and displays the short wavelength emission. Rigidification of the tetrapyridyl ligand does not improve the emission yield, a fact which is in agreement with the above explanation. Absorption and emission spectra for all these compounds are analyzed.
UPY-F is a software dedicated to solving various queries issued by end-users of spectrofluorimeters when they come across a problem in the course of an experiment. The main goal is to provide a diagnostic for the nonpertinent use of a spectrofluorimeter. Many artifacts may induce the operator into trouble and except for experts, the simple manipulation of the controls of a fluorimeter results in effects not always fully appreciated. The solution retained is an association between a powerful hypermedia tool and an expert system. A straight expert system offers a number of well-known advantages. But it is not well accepted by the user due to the many moves between the spectrofluorimeter and the diagnostic tool. In our hypermedia tool, knowledge can be displayed by the means of visual concepts through which one can browse, and navigate. The user still perceives his problem as a whole, which may not be the case with a straight expert system. We demonstrate typical situations in which an event will trigger a chain reasoning leading to the debugging of the problem. The system is not only meant to help a beginner but can conform itself to guide a well trained experimenter. We think that its functionalities and user-friendly interface are very attractive and open new vistas in the way future users may be trained, whether they work in research labs or industrial settings, as it could namely cut down on the time spent for their training.
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