Characterization of monofluorinated polycyclic aromatic compounds by ¹H, ¹³C and ¹⁹F NMR spectroscopy

Abstract

Monofluorinated polycyclic aromatic hydrocarbons (F-PAHs) have attracted much attention in analytical, environmental, toxicological and mechanistic studies because of their physico-chemical properties, which are closely similar to those of the parent PAHs. Because of this, full NMR characterization has become of interest. Complete 1H, 13C and 19F NMR chemical shifts, and also 1J(H,C), (n)J(C,F), (n)J(H,F) and (n)J(H,H) coupling constants, have been assigned for the F-PAHs 1-fluoronaphthalene, 2-fluorofluorene, 5-fluoroacenaphthylene, 2-fluorophenanthrene, 3-fluorophenanthrene, 3-fluorofluoranthene, 1-fluoropyrene, 1-fluorochrysene, 2-fluorochrysene, 3-fluorochrysene and 9-fluorobenzo[k]fluoranthene. To allow comparison with the corresponding parent PAHs, the 1H and 13C chemical shifts of acenaphthylene, phenanthrene, fluoranthene, pyrene and benzo[k]fluoranthene were determined. Chemical shift increments and the effects on the coupling constants from the fluorine substitution are discussed.

Pinpoint-fluorinated polycyclic aromatic hydrocarbons (F-PAHs): Syntheses of difluorinated subfamily and their properties

“…As an exception, 6,7-difluoropicene (6h, CCDC 1545329) has a large C6-C6a-C6b-C7 torsion angle (26.9°), which is ascribed to the repulsive interaction between the two fluorine atoms. It must be emphasized that the chemical shifts of the 19 F NMR signals for pinpoint-fluorinated PAHs 2c [6a], 6g, and 6i were fully consistent with the rule described above (Figure 7). Therefore, their structures were determined not by single crystal X-ray structure analysis but by 19 F NMR.…”

“…The required 1,1,2-trifluoro-1-alkenes were prepared by the Negishi coupling of a trifluorovinylzinc(II) complex with the corresponding aryl triflates or iodides [13]: Trifluorovinyllithium, which was generated from commercially available 1,1,1,2-tetrafluoroethane and LDA (2.0 equiv), was treated with zinc dichloride in the presence of TMEDA at -78 °C (Scheme 2). 19 F NMR analysis indicated that trifluorovinylzinc(II) chloride-TMEDA complex 3 (65% yield based on ZnCl 2 ) was obtained along with an inseparable bis(trifluorovinyl)zinc complex (16% yield).…”

“…In this paper, the syntheses of pinpoint-difluorinated PAHs involving the Pd(II)-catalyzed Friedel-Crafts-type cyclization of 1,1,2-trifluoro-and 1,1-difluoro-1-alkenes and the In(III)-catalyzed Friedel-Crafts-type cyclization of 1,1-difluoroallenes are described. The assembly of an array of difluorinated PAHs formed via these protocols and previously reported monofluorinated PAHs, which mainly comprised phenacenes, enabled studies of their physical properties such as solubility, downfield shift in 19 F NMR spectroscopy, and HOMO/LUMO energy gap.…”

Fluorination of Bi- and polycyclic aromatic hydrocarbons with N-fluorobis(phenylsulfonyl)amine in the absence of solvent

“…The structure of compounds obtained was confi rmed by 1 H and 19 F NMR spectra and GC-MS data. The spectral characteristics were consistent with the published data for 1-fl uoro-, 2-fl uoro-, 1,4-difl uoronaphthalene [26,38,39], 1-methyl-2-fluoro-, 1-methyl-4-fluoro-, 1-methyl-5-fluoro-, 1-methyl-8-fl uoronaphthalene [19], 1-fl uoro-, 3-fl uoro-, 4-fl uoro-, 9-fl uoro-, 9,10-difl uorophenanthrene [32,34,40], 9-fl uoro-, 9,10-difl uoroanthracene [35], 1-fl uoro-, 4-fl uoropyrene [35,40].…”

High‐Yielding Synthesis and Full Spectroscopic Characterization of 5,6:11,12‐Di‐o‐phenylenetetracene and Its Synthesis Intermediates

“…These spin systems can be approximately attributed to the naphthacenic (I, H3-H6/H11-H14) and phenylenic (II, H7-H10/ H15-H2) rings of DOPT by comparison with the reported 1 H NMR data of unsubstituted naphthacene [54,55] and of the data of 3,4-o-phenylenefluoranthene [55] with fluoranthene. [56] Therefore the most downfield signal at δ = 8.43 ppm (A1A1′) was assigned to the supposed most deshielded protons H3/H6/H11/ H14 of the substituted naphthacenic core. In consequence, the less downfield signal at δ = 7.91 ppm (A2A2′) of spin system II presumably corresponds to the protons H2/H15/H7/H10 of both pseudo-isolated phenylenes orthogonal to the fully conju- …”