Hetero-Polymetallic Complexes Incorporating Luminescent Lanthanide Ions

Abstract

The long-lived f-centred luminescence of lanthanide chelates is of considerable interest for the development of luminescent molecular probes in cellular imaging and bioassay and as dopants in light emitting devices. The intermetallic communication in molecular hetero-polymetallic compounds containing f and s or p block ions, d and f block ions and different f-block ions opens up new avenues in FRET assays, directional light conversion, colour tuning and mixing, and the combination of multiple molecular imaging techniques (e.g. optical-MRI) that, particularly when coupled with time-gating protocols, can eliminate competitive fluorescence from endogenous molecules. In all these applications, the focus remains on optimising the luminescence properties of the assemblies by directing the energy transfer processes involved. In this short review, an account of recent findings in the area of luminescent hetero-polymetallic lanthanide complexes is presented, focussing on the different synthetic strategies employed to construct s-f, p-f, d-f and f-f arrays. An evaluation of the energy transfer processes and photophysical properties of this genre of compounds is provided, with specific emphasis on potential applications. Keywords: Energy transfer, hetero-polymetallics, lanthanide complexes, luminescence, FRET assays, optical-MRI, Polymetallic MRI, emitting diodes (OLED's), Laporte's rule, tris-thionapththolate