No abstract

Transition metal lumophores are now well established as agents for cell imaging, but we are still not able to predict generally and with confidence their cellular localisation, or, for that matter, their uptake efficiencies. While many such complexes have been shown to illuminate cells, genuine applications in biomedical research will only be developed when their uptake and localisation are better understood. This perspective is not a comprehensive review of luminescence, but is an overview of attempts to control uptake and localisation, focussing on a personal account of this group's development of imaging agents based on the Re(CO)(3) bipyridine core, and our attempts to understand and control their cellular behaviour.

A series of mono- and dimetallic Au(I) triphenylphosphine complexes derived from 1,2-, 1,4-, and 1,8-dialkynyloxyanthraquinone have been prepared. The photophysical and cytotoxic behavior of the ligands and complexes have been explored, with all of the complexes showing both appreciable cytotoxicity against the MCF-7 carcinoma cell line and useful room-temperature anthraquinone-based visible luminescence, which allowed their successful application as fluorophores in cell imaging microscopy. The implications of the photophysical and toxicological properties for the design and investigation of gold-based anticancer agents are discussed.

A range of luminescent, dimetallic complexes based upon the rhenium fac-tricarbonyl diimine core, linked by aliphatic chains of varying lengths and functionality, have been synthesized and their photophysical properties examined. Each complex displays characteristic (3)M(Re)L(diimine)CT emission in aerated acetonitrile solution, with long lifetimes in the range of 129-248 ns and corresponding quantum yields in the range 3.2-8.0%. In aqueous solution, as opposed to acetonitrile, the complexes generally show a small hypsochromic shift in λ(em) and an extension of the (3)MLCT lifetime, attributed to a hydrophobically driven association of the alkyl chains with the rhenium-bound diimine units. In live cell imaging experiments using MCF7 cells the complexes all show good uptake by non-energy dependent mechanisms without endosomal entrainment, and with varying propensity to localize in organelles. The degrees of uptake and localization properties are discussed in terms of the length and chemical nature of the linkers, and in terms of the likely interactions between these and the various cellular components encountered.

We report highly unusual photophysical properties of a fac-Re(CO) 3 -bisthiazole complex, which is shown to break the Kasha-Vavilov rule. Herein, we show that such a complex has unusual emission wavelength variation due to the presence of photo-induced isomerisation from the stable, ground-state N,N-bound thiazole complex to S,N-and S,S-donation in the photo-induced excited state. A triple excitation, triple emission profile along with extensive DFT calculations support this theory to showcase an unusual circumstance of suulfur donation to the fac-Re(CO) 3 core upon luminescence. fac-Rhenium tricarbonyl complexes are extensively studied due to their fluorescent properties, high stability, and ready incorporation into conjugates with broad applicability in imaging and targeting. The spectroscopic features of the complex under study have broad fundamental interest while also offering potential for design of novel agents for use in biological imaging studies.