Dibenzothiophene emission

A novel, short-lived (< 10 sec) visible luminescence has been observed when dibenzothiophene is excited by an unfocused ruby laser. The luminescence occurs throughout the visible region and bears no resemblance to either normal fluorescence or phosphorescence. It is thought that a molecular fragmentation is involved which is followed by a chemiluminescent emission. 

More than 70 individual sulfur species were further identified by gas chromatography-atomic emission detection (GC-AED) and by gas chromatography-mass spectroscopy (GC-MS) (12). Figure 5 illustrates the composition of the sulfur components of the gas oil. The major components are individually identified on the figure. It can be seen that alkylbenzothio-phenes and dibenzothiophenes are the major components. The size of the alkyl substituents ranges up to 16 carbons on benzothiophene and up to 7 carbons on dibenzothiophene. 

Pine needles from the surroundings of metal reclamation plant probably contained PCDTs in low concentrations. Quantitative determinations were not made due to much interference by other compounds of similar type [49]. The concentrations of TeCDDs were in the range of 5-50 pg/g per dry weight of needles and the concentrations of TeCDFs in the range of 4-15 pg/g. Quite high concentrations of alkylated dibenzothiophenes in pine needles in a recipient area of the emissions from a pulp and paper mill have been measured, which might suggest that PCDTs could also be taken up by needles [56]. 

Similar CT states can be formed when PF chains are copolymerized with good charge acceptors. This strategy is now frequently used to improve the charge balance in devices and can have profound impact on the photophysics of these materials via the creation of emissive charge transfer states. Figure 14 shows the absorption and emission spectra, in toluene and chloroform, two solvents with different polarity, of PFO containing dibenzothiophene-... 

All the thioethers are liquids at 60°C with the exception of dibenzothiophene. The reactions were performed neat, except dibenzothiophene was reacted in toluene. High yields are obtained. In the absence of sodium molybdenate and tri-n-butylamine the reactions were very slow. There was no evidence for tar formation in the catalysed reactions. The reactions were worked-up by washing with dilute acid. Phase separation was achieved easily. This effectively removed from the product the molybdate (<50 ppm by ion coupled plasma emission spectroscopy) and amine (<0.1% by gas chromatography). 

Atomic emission detectors (AEM) in the carbon- and sulfur-selective modes have been used for the analysis of thiaarenes (references in Herod 1998 Mossner and Wise 1999), and to determine the contents of benzothiophene, dibenzothiophene, naphthothiophenes, phenan-thro[4,5-focd]thiophene, and benzo[fr]naphtho[2,l-d]thiophene in NIST samples of coal tar, crude oil, and shale oil (Schmid and Andersson 1997). The sulfur-selective detector has also proved valuable for the analysis of sulfones in environmental samples 0anak et al. 1998). 

An elegant method in induce phosphorescence emission from a guest exploits the heavy-atom effect of heptakis(6-Br-6-deoxy- -CD). In nitrogen-purged dimethylformamide/water (4/1), solution phosphorescence emission from five polynuclear aromatic hydrocarbons (PNA), diben-zofuran, and dibenzothiophene was readily observed in the presence of 10" Br-functionalized P-CD [191]. 

Figure 4,7 Molecular structure and temperature dependence of (a, b) FSF and (c, d) FASAF emission spectra in ethanol. Dual emission is observed with isoemissive points below 230 K for both compounds. Adapted with permission from Figure 6 of F. B. Dias, 5. Pollock, C. Hedley, L. O. Palsson, Andy Monkman, 1.1. Perepichka, I. F. Perepichka, M. Tavasli and M. R. Bryce, Intramolecular charge transfer assisted by conformational changes in the excited state of fluorene-dibenzothiophene-S,S-dioxide co-oligomers, J. Phys. Chem. B, 110, 19329 19339 (2006). Copyright 2006 American Chemical Society...

Several random fluorene-dibenzothiophene copolymers 67a-e [106,107] have been reported. The meta linkage in the dibenzothiophene in copolymers 67a-e hinders the conjugation, resulting in a hypsochromic shift of the emission bands to the deep-blue color region (kmax 420 and 440 nm) [106]. Furthermore, hindered conjugation and hindered n-aggregation suppress the parasitic green emission at 520 nm in the solid state of the polymer, often observed in polyfluorenes. 

S. M. King, I. I. Perepichka, I. F. Perepichka, F. B. Dias, M. R. Bryce, A. P. Monkman, Exploiting a dual fluorescence process in fluorene-dibenzothiophene-5,5-dioxide co-polymers to give efficient single polymer LEDs with broadened emission, Adv. Funct. Mater., 19, 586-591 (2009). 

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