Excited state dependent electron transfer of a rhenium-dipyridophenazine complex intercalated between the base pairs of DNA: a time-resolved UV-visible and IR absorption investigation into the photophysics of fac-[Re(CO)3(F2dppz)(py)]+ bound to either [poly(dA-dT)]2 or [poly(dG-dC)]2.

The transient species formed following excitation of fac-[Re(CO)(3)(F(2)dppz)(py)](+) (F(2)dppz = 11,12-difluorodipyrido[3,2-a:2',3'-c]phenazine) bound to double-stranded polynucleotides [poly(dA-dT)](2) or [poly(dG-dC)](2) have been studied by transient visible and infra-red spectroscopy in both the picosecond and nanosecond time domains. The latter technique has been used to monitor both the metal complex and the DNA by monitoring the regions 1900-2100 and 1500-1750 cm(-1) respectively. These data provide direct evidence for electron transfer from guanine to the excited state of the metal complex, which proceeds both on a sub-picosecond time scale and with a lifetime of 35 ps, possibly due to the involvement of two excited states. No electron transfer is found for the [poly(dA-dT)](2) complex, although characteristic changes are seen in the DNA-region TRIR consistent with changes in the binding of the bases in the intercalation site upon excitation of the dppz-complex.

Solvent dependent photophysics of fac-[Re(CO)(3)(11,12-X(2)dppz)(py)](+)(X = H, F or Me).

The photophysical properties of [Re(CO)(3)(dppz)(py)](+) (dppz = dipyrido-[3,2-a:2',3'-c] phenazine) and its 11,12 substituted derivatives [Re(CO)(3)(dppzMe(2))(py)](+) and [Re(CO)(3)(dppzF(2))(py)](+) have been examined in organic and aqueous environments using phosphorescence and picosecond transient visible and infrared absorption spectroscopic methods. The roles of the intraligand IL(pi-pi*) and metal-to-ligand charge transfer MLCT(phz) excited states are evaluated and used to explain the major effect of difluoro-substitution, which is particularly remarkable in water, where the excited state of [Re(CO)(3)(dppzF(2))(py)](+) is strongly quenched.

Real-time detection of hyperosmotic stress response in optically trapped single yeast cells using Raman microspectroscopy.

Living cells survive environmentally stressful conditions by initiating a stress response. We monitored changes in the Raman spectra of optically trapped Saccharomyces cerevisiae yeast cell under normal, heat-treated, and hyperosmotic stress conditions. It is shown that when glucose was used to exert hyperosmotic stress, two chemical substances-glycerol and ethanol-can be monitored in real time in a single cell.

The photophysics of fac-[Re(CO)3(dppz)(py)]+ in CH3CN: a comparative picosecond flash photolysis, transient infrared, transient resonance Raman and density functional theoretical study.

The photophysical properties of fac-[Re(CO)3(dppz)(py)]+ (1, where dppz = dipyrido[3,2-a: 2',3'-c]phenazine) in CH3CN have been investigated using a series of complementary techniques including visible and infrared transient absorption and resonance Raman spectroscopy on the picosecond and nanosecond timescales. The results confirm previous reports that the lowest-lying emissive state in 1 is a triplet intra-ligand (3IL) state localised on the dppz ligand and have provided detailed information on the dynamics of 1 upon photoexcitation, including the relative energies of the excited state species encountered and the electronic distribution within these. If the dppz ligand is viewed in terms of phenanthroline (phen) and phenazine (phz) moieties, the emissive state is probably more accurately described as a 3 pi-->pi *(phz) IL state. The picosecond studies have shown that this emissive state is formed, at least in part, within 30 ps of excitation from a precursor, which is possibly a 3 pi-->pi *(phen) IL state. On the nanosecond timescale, TRIR has been employed to elucidate further dynamics and reveal the presence of an energetically close-lying state in equilibrium with the emissive state. This has tentatively been assigned as being 3d pi(Re)-->pi *(phz) metal-to-ligand charge transfer (MLCT) in nature. A summary of the photophysics is proposed in the form of a Jablonski scheme. Time dependent density functional theory (TD-DFT) calculations support the relative ordering and suggested electronic character of the excited state species involved.