5,6-BIS(9-(2-DECYLTETRADECYL)-6-FLUORO-9H-CARBAZOL-3-YL)NAPHTHO...
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described. The introduction of the carbazole fragment and PdCl2(dppf) as catalysts gave target compound—
gives a great advantage for several reasons: first, since
the fluorene moiety is rather electronegative, the addi-
tion of the electron-donating nitrogen atom somewhat
increases the electron density in the carbazole moiety
so that the HOMO energy of polymers based on car-
bazole-containing monomer M1 increases and
approach the HOMO energy of the ideal polymer. The
presence of the N–H group in carbazole makes it pos-
sible to introduce alkyl substituents that promote good
solubility in organic solvents. In addition, the substi-
tution of the benzene nucleus in benzodithiophene
(BDT) by a more electron-withdrawing naphthalene
nucleus in compound M1 leads to a decrease in the
bandgap width and to a lowering of the HOMO
energy. The introduction of fluorine atoms into the
main or side chains also contributes to a decrease in
the HOMO energy without a significant change in the
LUMO energy, as well as to the formation of an
ordered structure due to intra- and intermolecular C–
H…F…S interactions [8, 9].
5,6-bis(9-(2-decyltetradecyl)-6-fluoro-9H-carbazol-
3-yl)naphtho[2,1-b:3,4-b']dithiophene (М1)—as a
light oily product in 61% yield.
The composition and structure of intermediate
compounds and target product M1 have been proved
by elemental analysis data and 1H, 13C, and 19F NMR.
The aromatic region of the 1H NMR spectrum of M1
(Fig. 1a) shows one singlet, four doublets, three dou-
blets of doublets, and one triplet of doublets. The sin-
glet at δ = 8.52 ppm corresponds to the protons of the
benzene ring of the naphthalene moiety. Two doublets
at δ 8.03 (d, J = 5.4 Hz) and 7.51 ppm (d, J = 5.4 Hz)
arise from the Н(b) and H(a) protons of the fused
thiophene rings, respectively.
The doublet at δ = 7.14 ppm has the spin coupling
constant (SCC) J = 8.6 Hz; the same SCC is observed
for a more complicated signal at 7.30 ppm (dd, J1 =
8.6 Hz, J2 = 1.5 Hz). It is clear from the figure that
these two signals are from the aromatic protons Н(f)
and Н(e) in the ortho position to each other, and the
latter is coupled to the Н(d) proton in the meta posi-
tion (the corresponding SCC is 1.5 Hz). The doublet
at δ = 8.21 ppm shows a similar splitting (1.4 Hz);
hence, it corresponds to the Н(d) proton.
RESULTS AND DISCUSSION
Monomer M1 was synthesized according to
Scheme 1 through the reaction of p-fluorophenylhy-
drazine hydrochloride (1) with cyclohexanone to give
6-fluoro-2,3,4,9-tetrahydro-1H-carbazole (2) in 84%
yield. Then, compound 2 was treated with a iodine
solution in dimethyl sulfoxide at 115°C. The resulting
mixture was placed into an autoclave, where triethyl-
amine and a catalyst (10% Pd on carbon) were added,
and hydrogenated at a pressure of 20 atm and 60°C for
5 h; this treatment led to 3-fluoro-9H-carbazole (3) in
80% yield as a light beige powder.
Then, carbazole derivative 3 was alkylated with 1-
bromo(2-decyltetradecane) to give 9-(2-decyltetrade-
cyl)-3-fluoro-9H-carbazole (4); further reaction of 4
with N-bromosuccinimide and bis(pinacolato)dibo-
ron catalyzed by PdCl2(dppf) led to oily 9-(2-decyltet-
radecyl)-3-fluoro-6-(4,4,5,5-tetramethyl-1,3,2-
dioxoborolan-2-yl)-9H-carbazole (6) in 58% yield.
The triplet of doublets at δ 7.21 ppm (td, J1 = 8.9 Hz,
J2 = 2.5 Hz) arises from the H(h) proton in the ortho
position to the F and Н(g) atoms; the doublet splitting
(J = 2.5 Hz) is due to the coupling to Н(i). The signal
of the H(g) proton is observed at 7.27 ppm (dd, J1 =
4.1 Hz, J2 = 8.0 Hz) and is partially overlapped by the
solvent signal. The signals in the aliphatic region at δ =
4.03 (d, J = 7.3 Hz, 2Н), 2.08 (m, 1Н), and 0.94 ppm
(t, 7.3 Hz) correspond to the protons of the CH2 group
directly bonded to the nitrogen atom, to the H atom of
the tertiary CH group, and to the terminal CH3
groups, respectively. The other broadened signals in
the alkyl region arise from the methylene protons of
the alkyl substituents. The integrated intensities of all
the signals correspond to the suggested structure.
13
The aromatic region of the C NMR spectrum
Then, the bromination of o-dimethoxybenzene
with N-bromosuccinimide led to 1,2-dibromo-4,5-
dimethoxybenzene (8) as large white crystals in 92%
yield, and its reaction with thiophene-3-boronic acid
under Suzuki conditions gave 1,2-bis(thiophen-3-yl)-
4,5-dimethoxybenzene (9) in 85% yield. Treatment of
compound 9 with anhydrous iron chloride in nitro-
methane and then with BBr3 led to oxidative cycliza-
shows 20 signals; in particular, the doublet at δ 156–
1
158 ppm (d, JC–F = 238.0 Hz) is due to the carbon
atom bonded to the fluorine atom. The assignment of
the other signals was performed using heteronuclear
2D NMR. Analysis of the spectrum of (1Н, 13С) single
bond correlations (Scheme 2) demonstrates that the
signals at δ 129.15, 126.66, 123.74, 123.03, 121.69,
113.23 (d,
2JС–F = 25.4 Hz), 109.45 (d, 3JС–F = 8.9 Hz),
tion to form 5,6-dimethoxynaphtho[2,1_b:3,4_b']di-
thiophene (10) (yield 49%) and compound 11 (yield
99%), respectively.
2
108.54, and 106.00 (d, JС–F = 23.5 Hz) arise from
nine aromatic carbon atoms С19, С6, С1, С2, С9,
С14, С15, С18, and С12, respectively.
The reaction of compound 11 with [CF3(SO2)]2О
in the presence of triethylamine gave intermediate
bis(triflate) compound 12 in 72% yield. At the last
stage, the reaction of twofold molar excess of com-
This signals has been assigned owing to the exis-
tence of direct C–H coupling. The signals of quater-
nary aromatic C atoms have been assigned using the
pounds 6 and 12 in the presence of sodium carbonate (13С, 1Н) multiple bond correlation spectrum
DOKLADY CHEMISTRY Vol. 482 Part 2 2018