Time-resolved absorption photophysical properties

The photophysical properties of [Ru(TBP)(CO)(EtOH)], [Ru(TBP)(pyz)2], [Ru(TBP)(pyz)] (Fl2TBP = 5,10,15,20-tetra(3,5-tert-butyl-4-hydroxyphenyl)porphyrin) have been investigated by steady-state and time-resolved absorption and emission spectroscopies. The complexes are weakly luminescent, and the origins of this behavior is discussed.Transient Raman spectroscopic data have been reported for [Ru(TPP)(py)2], [Ru(TPP)(CO)(py), and [Ru(TPP)(pip)2] (pip = piperidine),and nanosecond time-resolved resonance Raman spectroscopy has been used to examine the CT excited states of [Ru(0EP)(py)2] and [Ru(TPP)(py)2]. " ... 

Samanta, A., Devadoss, C., and Fessenden, R.W., Picosecond time-resolved absorption and emission studies of the singlet excited states of acenaphthylene, /. Phys. Chem., 94,7106, 1990. Dunsbach, R. and Schmidt, R., Photophysical properties of some polycyclic conjugated hydrocarbons containing five-membered rings, /. Photochem. Photobiol. A Chem., 83, 7, 1994. 

A number of cyano-bridged complexes are included here even though they strictly do not fall in the general family-type defined for the section. The syntheses and photophysical properties of [(NC)(bpy)2Ru(/r-NC)Cr(CN)5] and [(NC)5Cr(Ai-CI Ru(bpy)2(M-NC)Cr(CN)5] have been described. Absorption of visible light by the Ru(bpy)2 unit results in phosphorescence from the Cr(CN)g luminophore, and the results evidence fast intramolecular exchange energy transfer from the MLCT state of the Ru(bpy)2 chromophore to the doublet state of the Cr -based unit. Time-resolved resonance Raman and transient UV-vis absorption spectroscopies have been employed to investigate the MLCT excited states of [(NC)(bpy)2Ru(//-CN)Ru (bpy)2(CN)], [(NC)(bpy)2Ru(//-CN)Ru(phen)2(CN)]+, [(NC)(phen)2Ru(//-CN)Ru (bpy)2(CN)]+, [(NC)(bpy)2... 

Investigations into the absorption and emission properties are especially important since they can reveal if the photophysical properties of the molecular components are different when immobilized, compared to when they are dissolved in solution. These investigations typically involve both steady-state and time-resolved methods. Time-resolved or transient techniques yield information about the lifetime of the emitting state, while flash photolysis yields the absorption characteristics of the photochemically produced transient species. Information of this kind is essential for understanding the interactions between the molecular... 

A, A -dimethylaniline group has been synthesized by a copper-free Sonogashira cross-coupling reaction using microwave irradiation as the source of energy <2006EJO2344>. The electrochemical and photophysical properties of the triad were systematically investigated by techniques such as time-resolved fluorescence and transient absorption spectroscopy. 

What is not discussed at length are photophysical phenomena in SCF solvents (e.g. fluorescence quenching, triplet-triplet annihilation, charge transfer, and exiplex formation) which have been extensively used to probe SCF properties, in general, and have been especially informative regarding the existence of clusters (solvent-solute and solute-solute) and their effect on reactivity. Absorption and fluorescence spectroscopy (both steady state [21-33] and time resolved [34-40], vibrational spectroscopy [41-44] pulse radiolysis, [45] and EPR [46,47] have all been utilized in this regard. 

Time-resolved measurements were initiated both by physicists, who were principally interested in photophysical processes that left the chemical structures of the molecules intact, and by chemists, who were mainly interested in the chemical alterations of the irradiated molecules, but also in the associated photophysical steps. The parallel development of these two lines of research is reflected in the terminology. For example, the term flash photolysis, as used by chemists, applies to time-resolved measurements of physical property changes caused by chemical processes induced by the absorption of a light flash (pulse). Flash photolysis serves to identify short-lived intermediates generated by bond breakage, such as free radicals and radical ions. Moreover, it allows the determination of rate constants of reactions of intermediates. Therefore, this method is appropriate for elucidating reaction mechanisms. 

The time-resolved luminescence of [Ru(bpy)3] has been deconvoluted into two components, and these have two different emission maxima (83). This observation suggests the existence of two distinct adsorption sites for [Ru(bpy)3] on laponite. At one type of the adsorption zone the water is held rigidly and presents an environment for the [Ru(bpy)3] probe that results in a short lifetime and a blue-shifted emission. The second absorption zone involves a stronger interaction directly with the clay surface such that the photophysics are less influenced by the nature of the surrounding water. This explanation was supported by a direct comparison of photophysical properties of the luminescence probe on the clay and in ice at - 20°C. 

Their photophysical properties were obtained by means of UV-Vis absorption, steady-state, and time-resolved photoluminescence spectroscopies. Figure 1 shows the typical UV-Vis absorption and emission spectra of SiHM/SiPhPPV and SiHM/SiPhPVK in chloroform. 

---