The proposed project is to prepare new molecules and materials which show efficient near-infrared luminescence, in the 1000 - 1500nm region, following excitation using long wavelength excitation in the 400 -1000nm region. Long-wavelength luminescence from lanthanides such as Yb(lll), Nd(lll), Pr(lll) and Er(lll) is of interest for applications varying from in vivo luminescent biomedical sensors to optical amplifiers in fibre-optic telecommunications networks, but in molecular compounds is usually stimulate d by UV excitation of aromatic ligands.
In this project, heteropolynuclear complexes will be prepared in which d-block chromophoric complexes, having intense absorption maxima at longer wavelengths (400 - 1000nm), will be connected to luminescent lanthani des by short bridging ligands which will permit rapid energy-transfer between the components. Thus, excitation of the d-block chromophore will result in sensitised luminescence in the near-infrared region from the lanthanide using wavelengths longer than h as previously been possible.
Two distinct approaches will be taken to the construction of appropriate materials. Firstly, discrete molecules will be prepared using a 'complexes as ligands' approach in which the d-block and f-block components are attached to a single bridging ligand in a stepwise manner. Secondly, coordination polymers will be prepared by co-crystallisation of anionic d-block chromophores (e.g. polypyridyl-cyanometallate complexes) with the desired lanthanide cations, to give solid-state materials.
The viability of both methods has been demonstrated by the applicants in preliminary experiments. The heteronuclear d-f complexes can be constructed with careful choice of d-block component, bridging ligand, and f-block component to optimise the photophysical properties of the complexes and generate new materials of interest for sensing and opto-electronic applications.
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