An extensive vibrational assignment of TTF and TTF-d4 is achieved, improving the previously reported one through the use of polarized infrared spectra of single crystals of the monoclinic form. Infrared spectra of the monoclinic and triclinic forms are compared and the different crystal field effects discussed. Powder Raman and infrared spectra of (TTF)Br1.0 and (TTF-d4)Br1.0, Raman depolarization ratios and infrared spectra of (TTF)ClO4 and (TTF-d4)ClO4 solutions are reported. The assignment of the ag, b1u, b2u, and b3u fundamental modes of (TTF)+ and (TTF-d4)+ radicals allows the identification of most of the relevant frequency shifts following the ionization of the TTF structure. The possible use of the ionization shifts for the study of the electronic charge distribution in the conducting TTF systems is considered. The parallel investigation of the concentration effects on the visible and infrared absorption spectra of TTF+ in solution let us to identify anomalous infrared absorptions associated with the formation of (TTF+)2 dimer. They are attributable to an intensity borrowing from the charge transfer band due to the electron–molecular vibration (e–mv) interaction and their identification opens the way to an experimental evaluation of the e–mv coupling constants of TTF.
Singlet oxygen sensitization by organic molecules is a topic of major interest in the development of both efficient photodynamic therapy (PDT) and aerobic oxidations under complete green chemistry conditions. We report on the design, synthesis, biology, and complete spectroscopic characterization (vis-NIR linear and two-photon absorption spectroscopy, singlet oxygen generation efficiencies for both one- and two-photon excitation, electrochemistry, intrinsic dark toxicity, cellular uptake, and subcellular localization) of three classes of innovative singlet oxygen sensitizers pertaining to the family of symmetric squaraine derivatives originating from pi-excessive heterocycles. The main advantage of pi-extended squaraine photosensitizers over the large number of other known photosensitizers is their exceedingly strong two-photon absorption enabling, together with sizable singlet oxygen sensitization capabilities, for their use at the clinical application relevant wavelength of 806 nm. We finally show encouraging results about the dark toxicity and cellular uptake capabilities of water-soluble squaraine photosensitizers, opening the way for clinical small animal PDT trials.
In principle, a population inversion in semiconductor quantum\ud
dots can be achieved through electrical, chemical or optical\ud
pumping. To date however, it has only been successfully\ud
demonstrated with optical pumping in the 1-photon absorption\ud
range (i.e., above the semiconductor bandgap). Under\ud
these conditions amplified stimulated emission (ASE) in 1-D\ud
waveguides and lasing within microsphere cavities and distributed\ud
feedback structures has been observed. In these studies,\ud
it was demonstrated that for the archetypal CdSe system,\ud
a given nanocrystal must encompass more than one electronhole\ud
(e–h) pair for a population inversion to be achieved. This\ud
value reflects the twofold degeneracy of the lowest electronic\ud
state in the wurtzite crystal structure
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