TIME-RESOLVED ABSORPTION, INFRARED, AND RESONANCE RAMAN-SPECTRA OF THE COMPLEXES [RU(X)(R)(CO)(2)(ALPHA-DIIMINE)] (X=HALIDE R=ALKYL) - INFLUENCE OF X ON THE CHARGE-TRANSFER CHARACTER OF THE LOWEST EXCITED-STATE

Nanosecond time-resolved absorption (TA), resonance Raman (TR(3)), and infrared (TRIR) spectra are reported for several complexes [Ru(X)(R)(CO)(2)(alpha-diimine)] (X = Cl, Br, I; R = Me, Et; alpha-diimine = N,N'-diisopropyl-1,4-diaza-1,3-butadiene (iPr-DAB), pyridine-2-carbaldehyde-N-isopropylimine (iPr-PyCa), 2,2'-bipyridine (bpy)). This is the first instance in which the TA, TR(3), and TRIR techniques have been used to probe excited states in the same series of complexes. The TA spectra of the iodide complexes show a transient absorption between 550 and 700 nm, which does not depend on the solvent but shifts to lower energy in the order iPr-DAB > bpy > iPr-PyCa. This band is assigned to an intraligand transition. For the corresponding chloride and bromide complexes this band occurs at higher energy, most probably because of a change of character of the lowest excited state from XLCT to MLCT. The TRIR spectra show an increase in v(CO) (and k(CO)) on promotion to the excited state; however, the shifts Delta v(CO) show a decrease in the order Cl- > Br- > I-. The TR(3) spectra of the excited complexes [Ru(X)(R)(Co)(2)(iPr-DAB)] show v(s)(CN) of the iPr-DAB ligand 50-80 cm(-1) lower in frequency than for the complexes in their ground state. This frequency shift decreases in the order Cl- > Br- > I-, indicating a decrease of CT character of the lowest excited state in this order. However, going from X = Br to I, the effect on Delta v(CO) is much larger than the decrease of Delta v(s)(CN). This different effect on the CO- and CN-stretching frequencies is assigned to a gradual change in character of the lowest excited state from MLCT to XLCT when Cl- is replaced by Br- and I-. This result confirms a similar conclusion derived from previous resonance Raman and emission experiments on these complexes.

Influence of water on the carbon dioxide absorption by 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide

The effect of the addition of water on the absorption of carbon dioxide by the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide was studied experimentally by measuring the low-pressure carbon dioxide solubility and the viscosity of the liquid solvent at temperatures from 303 to 323 K. Water is only partially miscible with the ionic liquid up to a mole fraction of 0.302 at 293 K, 0.321 at 303 K and 0.381 at 323 K. It was observed that the solubility of carbon dioxide decreases with the quantity of water from a mole fraction of 2.63 × 10-2 for the pure ionic liquid at 303.4 K to a value of 1.88 × 10-2, a reduction of 30% of the solubility, for a mole fraction of water of 0.28. The viscosity of the liquid solvent also decreases, up to 40% at 303 K, from 28.6 mPa s for the pure ionic liquid to 16.4 mPa s for a water mole fraction of 0.302.

Absorption and antioxidant effects of quercetin from onions, in man

Objective: To investigate the in vivo effects of quercetin following the ingestion of fried onions.

Thomson Scattering as a Diagnostic of Second-Harmonic Nd:YAG-Laser-Ablated Mg Plasma Plume

Thomson scattering is one of the most powerful diagnostic tools for plasma characterization, and it has been applied to a variety of plasmas. It is a nonintrusive technique, and the interpretation of the signal is relatively simple. However, this method has not been widely applied to low-temperature laser-ablated plasmas. Raman satellites have been observed in the scattering spectrum from a Mg laser-ablated plasma, giving this diagnostic the potential to be also used in density quantification of metastable states in plasmas.

Photochemical reduction of oxygen adsorbed to nanocrystalline TiO2 films: A transient absorption and oxygen scavenging study of different TiO2 preparations

Transient absorption spectroscopy (TAS) has been used to study the interfacial electron-transfer reaction between photogenerated electrons in nanocrystalline titanium dioxide (TiO2) films and molecular oxygen. TiO2 films from three different starting materials (TiO2 anatase colloidal paste and commercial anatase/rutile powders Degussa TiO2 P25 and VP TiO2 P90) have been investigated in the presence of ethanol as a hole scavenger. Separate investigations on the photocatalytic oxygen consumption by the films have also been performed with an oxygen membrane polarographic detector. Results show that a correlation exists between the electron dynamics of oxygen consumption observed by TAS and the rate of oxygen consumption through the photocatalytic process. The highest activity and the fastest oxygen reduction dynamics were observed with films fabricated from anatase TiO2 colloidal paste. The use of TAS as a tool for the prediction of the photocatalytic activities of the materials is discussed. TAS studies indicate that the rate of reduction of molecular oxygen is limited by interfacial electron-transfer kinetics rather than by the electron trapping/detrapping dynamics within the TiO2 particles.