Treatment of the
laser borane anti-B18H22 (compound 1) with iodine in ethanol gives the monoiodinated derivative
7-I-anti-B18H21 (compound 2) in 67% yield, or, by reaction with iodine or ICl in the
presence of AlCl3 in dichloromethane, the diiodinated derivative
4,4′-I2-anti-B18H20 (compound 3) in 85% yield. On excitation with
360 nm light, both compounds 2 and 3 give
strong green phosphorescent emissions (λmax = 525
nm, ΦL = 0.41 and λmax = 545 nm,
ΦL = 0.71 respectively) that are quenched by dioxygen
to produce O2(1Δg) singlet
oxygen with quantum yields of ΦΔ = 0.52 and
0.36 respectively. Similarly strong emissions can be stimulated via
the nonlinear process of two-photon absorption when exciting with
720 or 800 nm light. The high quantum yields of singlet-oxygen production,
coupled with the option of two-photon excitation, make compounds 2 and 3 promising O2(1Δg) photosensitizers. The molecular structures of compounds 2 and 3 were determined by single-crystal X-ray
crystallographic studies as well as multinuclear NMR spectroscopy
and mass spectrometry. Time-resolved UV–vis spectroscopy was
used to delineate their photophysical properties, and the electronic-structure
properties of the emitting species were determined by means of multiconfigurational
quantum-chemistry computations.
This work presents the fabrication of horizontally aligned PtSe2 films using one-zone selenization of pre-deposited platinum layers. We have identified the Se : Pt ratio as a parameter controlling the charge carrier mobility in the thin films.
A novel copolymer poly(thiophene-2,5-diyl-2,5-di-n-octyloxycarbonyl-1,4-phenylene), denoted as P33, is introduced as potential material for photovoltaics, polymer light-emitting diodes, and/or organic transistors. P33 dissolved in chloroform is investigated by steady-state absorption, linear/non-linear fluorescence spectroscopies and time-resolved fluorescence spectroscopy. Molar extinction coefficient, fluorescence quantum yield, and singlet fluorescence lifetime of P33 are determined to be 18,315 M cm, 0.4, and 810 ps, respectively. The P33 fluorescence fast components of decay times are 1.2 ps, 2.0 ps, and 0.5 ps for increasing wavelengths of 480 nm, 500 nm, and 520 nm, respectively. The fast component is attributed to a transport of nearly instantaneously formed excitons to localized states known as downhill energy transfer. Additionally multi-photon excited fluorescence is observed for pumping with wavelengths of 800 nm and 1200 nm. Two-photon absorption cross-section is determined to be 6.9 GM. These spectroscopic studies provide basic fluorescence characteristics of the novel thiophene copolymer P33.
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