Dibenzothiophenes spectra

In the UV spectrum of dibenzothiophene 5,5-dioxide zones B and C of the dibenzothiophene spectrum are still discernible and the 235 nm band in zone A is resolved into three distinct bands due to activation of the benzenesulfonyl chromophore. ... 

Ito and Matsuda studied the y-radiolysis of 2-methyltetrahydrofuran (MTHF) solutions of diphenyl sulfone and dibenzothiophene-S,S-dioxide (DBTSD) at 77 K. They found that the radical anions of these sulfone compounds are formed and have intense absorption bands at 1030 nm and 850 nm, respectively. The blue glassy solution of y-irradiated diphenyl sulfone has absorption bands at both 1030 nm and 360 nm while the absorption spectrum of the benzenesulfonyl radical formed by UV irradiation of diphenyl sulfone solution at 77 K showed only a peak at 382 nm. Gamma-irradiated phenyl methyl sulfone solution showed an absorption band only at 385 nm. Consequently the appearance of the absorption bands in 800-1030 nm of diphenyl sulfone and DBTSD may suggest that the unpaired electron is delocalized on two phenyl rings. The same authors studied the radiolysis of MTHF solutions of disulfones (diphenyl and dihexyl disulfones). They found a blue coloring of the solution by the y-radiolysis of diphenyl disulfone and dihexyl disulfone due to absorption peaks at 695 nm and 690 nm respectively, besides smaller absorptions at 300-400 nm. Comparing these results to the previous observation, that phenyl methyl sulfone solution absorbs only at 398 nm, results in the conclusion that the absorption band at 690 nm is due to the linked two sulfone moieties. The authors found that substituents on the phenyl ring lead to shifts in the absorption maxima of the... 

The 60 MHz NMR spectrum of dibenzothiophene has been measured in chloroform-di, carbon tetrachloride, and acetone. The 100 MHz spectrum, which is shown in Fig. 1, has been measured in... 

Fig. 1. NMK spectrum at 100 MHz of dibenzothiophene (CDCI3). Adapted from Balkau et al.

The spin-spin coupling constants for the spectrum of dibenzothiophene in carbon tetrachloride and acetone have been accurately determined by computer analysis and listed. In routine structural studies of derivatives of dibenzothiophene it is usually found that ortho-couplings are close to 8 Hz, meta couplings about 2 Hz and between 0.5 and 1 Hz. In chloroform-dj, H-2 and 3 in dibenzothiophene have the same chemical shift and the spectrum of 1,4-dimethyldibenzothiophene in this solvent also shows H-2,3 as a singlet at 87.03. Apart from the minimal coupling which has been detected between H-1,9 of 0.08 Hz, no interring coupling is observed in dibenzothiophenes. 

No significant pseudo-contact shifts could be induced in the spectra of dibenzothiophene, its sulfoxide, or its sulfone, with Eu(dpm)3 although a marked shielding of the protons of one ring was observed in the spectrum of the chromium tricarbonyl complex of dibenzothiophene,presumably due to a contact shift mechanism. 

The fragmentation of dibenzothiophene sulfoxide resembles that of dibenzothiophene rather than that of the sulfone. This is due to primary loss of 0 to give the dibenzothiophene ion, which is the strongest feature of the spectrum. Much of the breakdown which follows is due to that of the dibenzothiophene ion. There are, however, some aspects of sulfone behavior, notably the formation of the dibenzofuran ion (14) by the loss of sulfur from the rearranged molecular ion (13). ... 

Dibenzothiophene acts as a 7r-electron donor and readily forms complexes with known electron acceptors. In such cases the electronic spectrum of a solution of the two compounds shows a new absorption band, usually in the visible region. The order of donor strengths of several o,o -bridged biphenyls has been estimated from their respective charge-transfer spectra and found to be carbazole > fluorene > dibenzothiophene >dibenzofuran. Dibenzothiophene forms complexes with tetracy-anoethylene, various polynitro derivatives of fluorenone, > naphthalene-1,4,5,8-tetracarboxylic acid dianhydride, and tetra-methylmic acid. ... 

The spectrum for the interaction of dibenzothiophene with tetracy-anoethylene has been correlated with the calculated highest-occupied orbital energies of dibenzothiophene and used to obtain its ionization potential. ... 

The effects of concentration, rate of freezing, and solvent purity on the luminescence spectrum of dibenzothiophene have been studied.During slow freezing the molecules of the dissolved compound migrate toward the surface of the solvent crystals and thereby decrease the effective concentration. The effect on the triplet-singlet transition of introducing heavy atoms into the system has also been investigated by absorption measurements in benzene and ethyl iodide. ... 

The effect of the sulfone dipole on the ESR spectrum of the dibenzothiophene 5,5-dioxide anion has been examined, modified Hiickel calculations which ignored d-orbital conjugation predicting spin distributions which agreed with experimental data. Proton hyperfine splitting constants have also been obtained for the sulfone. Correlation with MO calculations shows that the sulfone group contributes a vacant symmetric orbital to the conjugated system. ... 

An analysis of the ESR spectrum of the dibenzothiophene radical anion46 yields the following hfs (hyperfine splitting) constants (gffuss) 5.16, 4.48, 1.46, and 0.86. The theoretical values based on HMO data for Model A2 are considerably smaller 2.84, 2.48, 1.47, and 0.27, respectively, which led the authors to make spin-density calculations by the Hartree-Fock method. Quite recently, the spin densities have been calculated for Model B (8S = 1, pcs = 0.566),466 and the following constants were obtained 5.03,3.99,0.75, and — 1.23. A study of the ESR spectrum of the radical derived from 2,8-dimethyl-dibenzothiophene permitted the assignment of the lowest hfe constant value to the proton in position 2. In contrast to the dithiins, experimental data for dibenzothiophene radicals are better reproduced by Model B. 

Hutchison reported the first ESR spectrum of a metastable phosphorescent state by study of naphthalene oriented in durene crystals.4 Since then, similar spectra have been recorded for several other polynuclear aromatics both oriented in host crystals and randomly suspended in glassy matrices. D values for all these ir,n excited states are quite low, indicating little interaction between the unpaired electrons. Interestingly, D for the quinolines equals 0.10cm"1 just as in naphthalene,197 indicating that the presence of a heteroatom does not necessarily change the ir,w nature of the lowest triplet state very much. A similar conclusion has been reached from a comparison of the ESR spectra of fluorene, carbazole, dibenzofuran, and dibenzothiophene.198... 

Thus, for example (Fields and Meyerson, 1966a), dibenzothiophene 5,5-dioxide (6) gives a 70 v. mass spectrum with the relative intensities shown in Table 1. 

Phthalic anhydride reacted with dibenzothiophene at 690° to give a 10% yield of addition and insertion products. Naphthobenzothiophene isomers, the addition products, were formed in a 2 1 ratio over phenyl-dibenzothiophene isomers, the insertion products—about the same ratio as was found in the reaction of benzyne with benzothiophene. The spectrum revealed no product of molecular weight 340, which would... 

The radical cation of dibenzothiophene 129 has been prepared in 1,1,1,3,3,3-hexafluoro-2-propanol solution by oxidation with Tl(OAc)3 and its EPR spectrum measured [274]. 

The mass spectrum of the octafluorodibenzotellurophene (47) has been determined.99 Comparison with the spectral data of the octafluoro derivatives of dibenzothiophene and dibenzoselenophene indicates that Te—C bonds are less stable under electron bombardment than those with Se—C or S—C bonds. 

---