2013-05-26 11:20:36 1276 Grilj, Jakob Zonca, Cedric Lawson Daku, Latevi Max Vauthey, Eric Physical Chemistry Chemical Physics Phys. Chem. Chem. Phys. 1463-9076 2012 14 6351 6358 HV http://pubs.rsc.org/en/Content/ArticleLanding/2012/CP/c2cp23577c http://pubs.rsc.org/en/content/articlepdf/2012/cp/c2cp23577c The photophysical properties of the free neutral radical galvinoxyl were studied by a combination of femtosecond time-resolved spectroscopy and quantum chemical calculations. The electronic absorption spectrum is dominated by an intense band at 430 nm that is ascribed to the D9,10←D0 transitions. Upon photoexcitation at 400 nm, the population of the D9,10 states decays within less than 200 fs to the electronic ground state. This ultrafast internal conversion does not involve intramolecular modes with large amplitude motion as the measured dynamics does not show any significant dependence on the environment, but is most probably facilitated by a high density of electronic states of different character. Depending on the solvent, a weak transient band due to the galvinoxylate anion is also observed. This closed-shell species, which is fluorescent although its deactivation is also dominated by non-radiative decay, is generated upon biphotonic ionization of the solvent and electron capture. The ultrashort excited-state lifetime of the galvinoxyl radical precludes photoinduced disproportionation previously claimed to be at the origin of the formation of both anion and cation.

]]> H204I408P1827 10.1039/c2cp23577c 20256 http://www.unige.ch/sciences/chifi/publis/pics/double/ref01276.png http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref01276.pdf 886 Pigliucci, Anatolio Duvanel, Guillaume Lawson Daku, Latevi Max Vauthey, Eric Journal of Physical Chemistry A J. Phys. Chem. A 1089-5639 2007 111 28 6135 6145 HV http://pubs.acs.org/cgi-bin/abstract.cgi/jpcafh/2007/111/i28/abs/jp069010y.html http://pubs.acs.org/cgi-bin/article.cgi/jpcafh/2007/111/i28/html/jp069010y.html http://pubs.acs.org/cgi-bin/article.cgi/jpcafh/2007/111/i28/pdf/jp069010y.pdf The influence of solute−solvent interactions on the vibrational energy relaxation dynamics of perylene and substituted perylenes in the first singlet excited-state upon excitation with moderate (<0.4 eV) excess energy has been investigated by monitoring the early narrowing of their fluorescence spectrum. This narrowing was found to occur on timescales ranging from a few hundreds of femtoseconds to a few picoseconds. Other processes, such as a partial decay of the fluorescence anisotropy and the damping of a low-frequency oscillation due to the propagation of a vibrational wavepacket, were found to take place on a very similar time scale. No significant relationship between the strength of nonspecific solute−solvent interactions and the vibrational energy relaxation dynamics of the solutes could be evidenced. On the other hand, in alcohols the spectral narrowing is faster with a solute having H-bonding sites, indicating that this specific interaction tends to favor vibrational energy relaxation. No relationship between the dynamics of spectral narrowing and macroscopic solvent properties, such as the thermal diffusivity, could be found. On the other hand, a correlation between this narrowing dynamics and the number of low-frequency modes of the solvent molecules was evidenced. All these observations cannot be discussed with a model where vibrational energy relaxation occurs via two consecutive and dynamically well-separated steps, namely ultrafast intramolecular vibrational redistribution followed by slower vibrational cooling. On the contrary, the results indicate that both intra- and intermolecular vibrational energy redistribution processes are closely entangled and occur, at least partially, on similar timescales.

]]> H222I443P430 10.1021/jp069010y 3591 http://www.unige.ch/sciences/chifi/publis/pics/double/ref00886.png http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref00886.pdf 630 Brendan P. Macpherson, Paul V. Bernhardt, Andreas Hauser, Stéphane Pagès, and Eric Vauthey Macpherson, Brendan P. Bernhardt, Paul V. Hauser, Andreas Pagès, Stéphane Vauthey, Eric Inorganic Chemistry Inorg. Chem. 0020-1669 2005 44 15 5530 5536 HV http://pubs.acs.org/cgi-bin/abstract.cgi/inocaj/2005/44/i15/abs/ic0506512.html http://pubs.acs.org/cgi-bin/abstract.cgi/inocaj/2005/44/i15/html/ic0506512.html http://pubs.acs.org/cgi-bin/abstract.cgi/inocaj/2005/44/i15/pdf/ic0506512.pdf Visible pump−probe spectroscopy has been used to identify and characterize short-lived metal-to-metal charge transfer (MMCT) excited states in a group of cyano-bridged mixed-valence complexes of the formula [LCo^IIINCM^II(CN)₅]^-, where L is a pentadentate macrocyclic pentaamine (L¹⁴) or triamine-dithiaether (L^14S) and M is Fe or Ru. Nanosecond pump−probe spectroscopy on frozen solutions of [L¹⁴Co^IIINCFe^II(CN)₅]^- and [L^14SCo^IIINCFe^II(CN)₅]^- at 11 K enabled the construction of difference transient absorption spectra that featured a rise in absorbance in the region of 350−400 nm consistent with the generation of the ferricyanide chromophore of the photoexcited complex. The MMCT excited state of the Ru analogue [L¹⁴Co^IIINCRu^II(CN)₅]^- was too short-lived to allow its detection. Femtosecond pump−probe spectroscopy on aqueous solutions of [L¹⁴Co^IIINCFe^II(CN)₅]^- and [L^14SCo^IIINCFe^II(CN)₅]^- at room temperature enabled the lifetimes of their Co^II−Fe^III MMCT excited states to be determined as 0.8 and 1.3 ps, respectively.

]]> P114 10.1021/ic0506512 3275 http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref00630.pdf