Thanks to their unique luminescence properties lanthanide chelates are often used as non-radioactive markers in a wide variety of applications such as diagnostics, research and high-throughput screening. Since they are known to have long decay-time luminescence (from few μs up to several ms) lanthanide chelates turn out to be ideal labels for time-resolved fluorometric assays. These methods are highly sensitive by reducing the background significantly compared to traditional prompt fluorescence measurements. Moreover one of the challenges in the design of luminescent lanthanide tags dedicated to bioanalyses and bioimaging applications, is to get an excitation wavelength as high as possible (especially wavelengths around or above 350 nm) since biomolecules are usually damaged by UV light. An Eu(III) chelate based on an original bis-pyridinylpyrazine structure has been synthesized and posseses an absorption maximum around 345 nm, which is significantly red-shifted in comparaison with commercial terpyridine-based Eu(III) chelate. Further amine derivatisation with homo-bifunctional cross-linking reagents allowed monoclonal antibodies labelling. The second aim of this work is to develop a new photoreactive lanthanide luminescent probe to specifically detect and react covalently with tagged proteins (polyHis or polyAsp) in order to determine in cellulo their distribution and their interactions with other proteins. Ideally, the recognition step would occur between the tag and the lanthanide cation followed by the covalent attachment event through photoactivation. This would result in a modulation of the signal emitted by the probe. To this end lanthanide chelates based on benzophenones, azido-coumarins and quinolinones were synthesized.