Ruthenium polypyridyl complexes with long aliphatic chains; photophysics, interfacial assembly and cell imaging

Abstract

A series of novel Ruthenium polypyridyl complexes [Ru(dpp)2(x-ATAP)](PF6)2 were synthesised and their photophysical and electrochemical properties are reported on, where x-ATAP is either 5-Amido-1,10-phenanthroline-(6-acetylthio-hexanyl), 5-Amido-1,10-phenanthroline-(8-acetylthio-octanyl), 5-Amido-1,10-phenanthroline-(11-acetylthio-undecanyl) or 5-Amido-1,10-phenanthroline-(16-acetylthio-hexadecanyl). These complexes exhibit bright emission. They are capable of self assembly on metallic surfaces. Furthermore, this series of complexes are capable of forming bilayer vesicle structures in aqueous conditions. Chapter 3 describes the synthesis, photophysics and solution phase electrochemistry of these complexes. The solvent dependence of the luminescence properties is also addressed along with the formation of bilayer vesicles of these compounds in aqueous conditions. In chapter 4 self assembled monolayers of the Ru(dpp)2(x-ATAP)](PF6)2 complexes were formed on platinum electrodes and these monolayers were characterized electrochemically. These monolayers were found to be somewhat unstable when analysed electrochemically even when backfilled with an appropriate length alkanethiol. Attempts to study the distance dependence of electron transfer reveal that these complexes when functionalized on metal surfaces lie flat on the surface as opposed to the ruthenium headgroup being raised above the surface. The photophysical properties of these monolayers on gold and platinum electrodes and gold nanoparticles are also reported. Despite the close proximity of the headgroup to the metal surface the monolayers remain luminescent and exhibit large SERS enhancement when absorbed on aggregated gold nanoparticle clusters. Chapter 5 explores the interactions of the Ru(dpp)2(x-ATAP)](PF6)2 complexes with monoclonal cells and their suitability as luminescence cell imaging probes. A CHO cell line (Chinese hamster ovary cell) were stained with the Ru(dpp)2(x-ATAP)](PF6)2. This series of complexes was capable of crossing the cell membrane barrier and localizing in discrete compartments of the cell. The stained cell line was imaged by FLIM (fluorescence lifetime imaging microscopy) and 3D z-stacked images of the cell were constructed. It was found that there was an alkyl chain length dependence on the localization of these complexes within the cell. Complexes with short alkyl chains stained throughout the cytoplasm and nucleus while the complexes with longer alkyl chains remain localized in endosomes. Finally chapter 6 explores a novel ruthenium(II) bis-terpyridyl type complex, [RuII(LKet)2].(PF6)2. This complex was characterized photophysically and electrochemically. By extending the structure of the 2,2';6',2"-terpyridine (tpy) ligands with carbonyl bridging units the ruthenium the [RuII(LKet)2].(PF6)2 complex cage structure is much closer to perfect octahedral configuration compared to [RuII(tpy)2]2+. The photophysical performance in ambient conditions of [RuII(LKet)2].(PF6)2 is massively increased compared to [RuII(tpy)2]2+ or similar complexes and this complex displays the longest luminescence lifetime of any ruthenium complex at 298 K and in aerated conditions to our knowledge. The long term aims of this work is to modify this complex with a long chain alkane or peptide for cell imaging purposes