Are silicone-supported [C60]-fullerenes an alternative to Ru(ii) polypyridyls for photodynamic solar water disinfection?

Different photosensitizing materials manufactured by immobilizing (0.5-3.0 g m-2) tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(ii) (RDP 2+), [C60]-fullerene, or 1-(4-methyl)-piperazinylfullerene (MPF) on porous neutral (pSil) or surface-modified anionic (pSil-) poly(dimethylsiloxane) are compared on the grounds of their singlet molecular oxygen (1O2) production and photodynamic solar water disinfection capability. The C60-based sensitizers display a broad weak absorption in the visible and strong absorption in the UV, while absorption of light by RDP2+ supported on pSil is strong in both the UV and blue regions. The 1O2 emission lifetimes (??) determined for RDP2+ and MPF on porous silicone materials under air are similar (40-50 ?s) and correspond to the decay of 1O2 generated by sensitizers dissolved in the polymer support. In contrast, ?? measured for C 60 in pSil is similar to that observed for MPF or RDP2+ when immobilized at low loading on pSil, but dramatically increases up to 5 ms if C60 aggregates are formed in the porous material as evidenced by microscopy evaluation. The photosensitizing properties of the dyes, together with their electrical charge and the overall charge of the porous silicone-based materials, lead to highly different sunlight-driven bacteria inactivation efficiencies, as tested with waterborne E. faecalis. RDP/pSil provides efficient disinfection by photosensitization unlike MPF/pSil, which leads to reduced bacteria inactivation rates due to poorer 1O2 production. C60/pSil and MPF/pSil- materials, despite their 1O2 photogeneration, show unsuccessful waterborne bacteria inactivation due to the negative surface charge of fullerene aggregates in contact with water, and to the net negative charge of the pSil-, respectively. This journal is Zapotitlán The Royal Society of Chemistry and Owner Societies

Detection of secondary structures in 17-mer Ru(II)-labeled single-stranded oligonucleotides from luminescence lifetime studies.

The emission properties of a non intercalating complex, [Ru(TAP)2(dip)]2+ (TAP = 1,4,5,8-tetraazaphenanthrene; dip = 4,7-diphenyl-1,10-phenanthroline), tethered to 17-mer single-stranded oligodeoxyribonucleotides (ODNs) either in the middle or at the 5'-end of the sequence, are determined. The results highlight the fact that the luminescence of this metallic compound is sufficiently sensitive to its microenvironment to probe self-structuration of these short single-stranded ODNs. It is shown that the weighted averaged emission lifetimes (tau(M)) along with the quenching rate constants of luminescence by oxygen reflect particularly well different structures adopted by the different ODNs sequences. The determination of these parameters thus offers an elegant way to examine possible structurations of synthetic single-stranded ODNs that play important roles in biological applications.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Photochemical Oxidation of Thioketones by Singlet Molecular Oxygen Revisited: Insights into Photoproducts, Kinetics, and Reaction Mechanism

Photosensitized oxidation of trimethyl[2.2.1]-bicycloheptane thioketones by 1 O2 can yield more photoproducts than exclusively ketones and sulfines. Moreover, the ketone/sulfine ratio can be reversed when protic conditions and high thioketone concentrations are used, conversely to earlier results reporting ketones as the main photoproducts. A new mechanistic proposal for sulfine formation is suggested following intermolecular oxygen transfer from a peroxythiocarbonyl intermediate to a second thioketone molecule. Reaction quantum yields (10−5−10−2) depend on the reaction conditions and time. Sulfine production reaches a maximum at short irradiation times, whereas decomposition to the corresponding ketone is observed at long reaction times. When the thioketone substrate has a hydrogen atom at the α position a peroxyvinylsulfenic acid intermediate can be formed by proton transfer. Reaction of this intermediate with another thioketone molecule can yield more sulfine and its tautomeric vinylsulfenic acid, which dimerizes in situ to the thiosulfinate. The hydroperoxyl group of the peroxyvinylsulfenic acid can also rearrange to the α position, and by reaction with the starting thioketone, α-hydroxy thioketone and additional sulfine can be formed, while dehydration yields the α-oxo thioketone. In situ [2 + 2] and [4 + 2] self-cycloaddition of the α-oxo thioketone yields significant amounts of the corresponding adducts at prolonged irradiation times

Luminescence quenching of Ru-labeled oligonucleotides by targeted complementary strands.

The yield of hole injection into guanines of different oligonucleotide duplexes by a photooxidizing tethered Ru(II) complex is examined by measuring the luminescence quenching of the excited complex. This yield is investigated as a function of the anchoring site of the complex (on a thymine nucleobase in the middle of the sequence or on the 5' terminal phosphate) and the number and position of the guanine bases as compared with the site of attachment of the Ru(II) compound. In contrast to other studies, the tethered complex, [Ru(tap)(2)(dip)](2+), is a non-intercalating compound and has been shown previously to produce an irreversible photocrosslinking between the two strands as the ultimate step of hole injection. The study of luminescence quenching of the anchored complex by emission intensity and lifetime measurements for the different duplexes indicates that a direct contact between the complex and the guanine nucleobase is needed for the electron transfer to take place. Moreover, for none of the sequences a clear contribution of a static quenching is evidenced independently of the two types of attachment of the [Ru(tap)(2)(dip)](2+) complex to the oligonucleotide. A comparison of the fastest hole-injection process by electron transfer to the excited anchored [Ru(tap)(2)(dip)](2+), with the rate of the photo-electron transfer between the same complex free in solution and guanosine-5'-monophosphate, indicates that the hole injection by the anchored complex is slower by a factor of 10 at least. A bad overlap between donor and acceptor orbitals is probably the cause of this slow rate, which could be attributed to some steric hindrance induced by the complex linker