Biologically Compatible, Phosphorescent Dimetallic Rhenium Complexes Linked through Functionalized Alkyl Chains: Syntheses, Spectroscopic Properties, and Applications in Imaging Microscopy

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 (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.

Single amino acid chelate complexes of the M(CO)3+ core for correlating fluorescence and radioimaging studies (M = 99mTc or Re)

“…Several rhenium polypyridyl‐based molecular probes have been described recently . One is described as a ‘sleeping Trojan horse’ because the complex acts as a vessel that is membrane impermeant when unoccupied but exhibits cellular uptake upon loading with metal ions.…”

“…While our initial studies focused on labelled peptides, subsequent results demonstrated that the SAAC concept is quite versatile and may be adapted to other biomolecules as diverse as biotin, folate, vitamin B 12 , insulin and thymidine . Several non‐SAAC‐band luminescent diimine derivatives of the fac ‐{Re(CO) 3 } + core are also described . In the course of these studies, some unusual photophysical effects have been encountered that will be discussed briefly.…”

Materials for FRET Analysis: Beyond Traditional Dye–Dye Combinations

“…These complexes have found particular application in cell imaging [9,[400][401][402][403][404]. Of the transition metals, ruthenium (Ru) complexes remain the most popular, however increasingly iridium (Ir), rhenium (Re), and occasionally osmium (Os) and platinum (Pt) have been used in cell imaging applications [9,[400][401][402][403][404][405]. The current factor limiting widespread adoption of these types of materials is probably commercial availability, as most of the materials are synthesized in-house.…”

Luminescent sensor for copper(II) ion based on imine functionalized monometallic rhenium(I) complexes

“…[2830], catalysis [31], light-emitting devices [32,33], CO2 fixation [34], optical switches [35,36], bioprobes [37,38] and imaging [39]. As far as we know, there is a limited number of reports available on rhenium(I) complexes attached to the imine ligands [4042].…”