DNA threading intercalation of enantiopure [Ru(phen)2bidppz]2+ induced by hydrophobic catalysis.

The enantiomers of a novel mononuclear ruthenium(ii) complex [Ru(phen)2bidppz]2+ with an elongated dppz moiety were synthesized. Surprisingly, the complex showed no DNA intercalating capability in an aqueous environment. However, by the addition of water-miscible polyethylene glycol ether PEG-400, self-aggregation of the hydrophobic ruthenium(ii) complexes was counter-acted, thus strongly promoting the DNA intercalation binding mode. This mild alteration of the environment surrounding the DNA polymer does not damage or alter the DNA structure but instead enables more efficient binding characterization studies of potential DNA binding drugs.

Excited State Dynamics of Bistridentate and Trisbidentate RuII Complexes of Quinoline-Pyrazole Ligands.

Three homoleptic ruthenium(II) complexes, [Ru(Q3PzH)3]2+, [Ru(Q1Pz)3]2+, and [Ru(DQPz)2]2+, based on the quinoline-pyrazole ligands, Q3PzH (8-(3-pyrazole)-quinoline), Q1Pz (8-(1-pyrazole)-quinoline), and DQPz (bis(quinolinyl)-1,3-pyrazole), have been spectroscopically and theoretically investigated. Spectral component analysis, transient absorption spectroscopy, density functional theory calculations, and ligand exchange reactions with different chlorination agents reveal that the excited state dynamics for Ru(II) complexes with these biheteroaromatic ligands differ significantly from that of traditional polypyridyl complexes. Despite the high energy and low reorganization energy of the excited state, nonradiative decay dominates even at liquid nitrogen temperatures, where triplet metal-to-ligand-charge-transfer emission quantum yields range from 0.7 to 3.8%, and microsecond excited state lifetimes are observed. In contrast to traditional polypyridyl complexes where ligand exchange is facilitated by expansion of the metal-ligand bonds to stabilize a metal-centered state, photoinduced ligand exchange occurs in the bidentate complexes despite no substantial MC state population, while the tridentate complex is extremely photostable despite an activated decay route, highlighting the versatile photochemistry of nonpolypyridine ligands.

Binding of Thioflavin-T to Amyloid Fibrils Leads to Fluorescence Self-Quenching and Fibril Compaction.

Thioflavin-T binds to and detects amyloid fibrils via fluorescence enhancement. Using a combination of linear dichroism and fluorescence spectroscopies, we report that the relation between the emission intensity and binding of thioflavin-T to insulin fibrils is nonlinear and discuss this in relation to its use in kinetic assays. We demonstrate, from fluorescence lifetime recordings, that the nonlinearity is due to thioflavin-T being sensitive to self-quenching. In addition, thioflavin-T can induce fibril compaction but not alter fibril structure. Our work underscores the photophysical complexity of thioflavin-T and the necessity of calibrating the linear range of its emission response for quantitative in vitro studies.

Extending charge separation lifetime and distance in patterned dye-sensitized SnO2-TiO2 µm-thin films.

A simple method for the preparation of patterned dye-sensitized SnO2-TiO2 thin films, designed to prolong the lifetime of the interfacial charge separated state is presented. Using microfluidic technology, the thin films were sensitized with the organic sensitizer D35 such that they contain SnO2-TiO2 areas with dye and SnO2 dye-free areas at which injected electrons can be accumulated. Single wavelength transient absorption spectroscopy confirmed significantly extended charge separation lifetime at the dye-semiconductor interface. Sufficiently high density of injected electrons results in substantial decrease of charge recombination rate constants (kcr); a factor of ∼50 compared to dye-sensitized TiO2 thin films and a factor of ∼2000 compared to dye-sensitized SnO2 thin films. Furthermore, the potential of this approach was confirmed by photoinduced conduction band mediated electron transfer from the dye to a model electron acceptor, Co protoporphyrin IX, which was adsorbed to the SnO2-only regions.

Correction: Long-lived charge separation in dye-semiconductor assemblies: a pathway to multi-electron transfer reactions.

Correction for 'Long-lived charge separation in dye-semiconductor assemblies: a pathway to multi-electron transfer reactions' by Elin Sundin et al., Chem. Commun., 2018, 54, 5289-5298.

Long-lived charge separation in dye-semiconductor assemblies: a pathway to multi-electron transfer reactions.

Solar energy has the potential of providing the world with clean and storable energy. In principle, solar fuels can be generated by light absorption followed by primary charge separation and secondary charge separation to reaction centres. However this comes with several challenges, including the need for long-lived charge separation and accumulation of several charges. This Feature Article focuses on how to achieve long-lived charge separation in dye sensitized semiconductor assemblies and the way towards multi-electron transfer through conduction band mediation, aiming at solar fuel generation. Herein, we discuss various examples of how the charge separated lifetime can be extended and potential ways of achieving one or multiple electron transfer in these assemblies.