Biologically compatible, phosphorescent dimetallic rhenium complexes linked through functionalized alkyl chains : syntheses, spectroscopic properties, and applications in imaging microscopy

Balasingham, Rebeca G. and Thorp-Greenwood, Flora L. and Williams, Catrin F. and Coogan, Michael and Pope, Simon J. A. (2012) Biologically compatible, phosphorescent dimetallic rhenium complexes linked through functionalized alkyl chains : syntheses, spectroscopic properties, and applications in imaging microscopy. Inorganic Chemistry, 51 (3). 1419–1426. ISSN 1520-510X

Abstract

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 3MReLdiimineCT 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 λem and an extension of the 3MLCT 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.