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Synthesis of compound 11
Under N2 gas, 8 (0.22 g, 1.3 mmol) was dissolved in 15 mL THF
and NaH (petroleum ether 60%, 0.065 g, 1.6 mmol) was added
under ice bath. The mixture was stirred for 0.5 h, and benzyl
bromide (0.18 mL, 1.5 mmol) in THF (5 mL) was added drop-
wise. Then the mixture was kept for 2 h under ambient
temperature, and water (25 mL) was added to nish the reac-
tion. Multiple extraction with CH2Cl2 combined with drying by
MgSO4. The ltrate was concentrated and puried by ash
column chromatography (CH2Cl2–CH3OH, 100 : 1, Rf ¼ 0.5) to
obtain the compound 11 (0.26 g, yield: 75%). 1H NMR (400 MHz,
CDCl3, d ppm) 8.32 (s, 1H), 8.12 (s, 1H), 8.01 (d, J ¼ 5.9 Hz, 1H),
7.87 (d, J ¼ 5.9 Hz, 1H), 7.68 (s, 1H), 7.40 (d, J ¼ 5.0 Hz, 2H), 7.34
(d, J ¼ 7.8 Hz, 3H), 7.23 (d, J ¼ 6.4 Hz, 2H), 5.43 (s, 2H), 1.55–
1.53 (m, 1H). MS (ES API+) m/z [C18H14N2 + H]+ calcd 259.3,
found: 259.2.
Scheme 2 Synthesis of compounds 3–5.
Synthesis of compound 12
Starting from compound 8 (0.20 g, 1.2 mmol) and penta-uoro-
benzyl bromide (0.21 mL, 1.4 mmol), compound 12 was
prepared according to the same procedure of compound 11 and
was puried by ash column chromatography (CH2Cl2–CH3OH,
100 : 1, Rf ¼ 0.4) (0.28 g, yield: 68%). 1H NMR (400 MHz, CDCl3,
d ppm) 8.32 (s, 1H), 8.12 (s, 1H), 8.01 (d, J ¼ 5.9 Hz, 1H), 7.87 (d, J
¼ 5.9 Hz, 1H), 7.68 (s, 1H), 7.40 (d, J ¼ 5.0 Hz, 2H), 7.34 (d, J ¼
7.8 Hz, 3H), 7.27–7.17 (m, 2H), 5.43 (s, 2H), 1.31 (t, J ¼ 231.6 Hz,
1H). MS (ES API+) m/z [C18H9N2 + H]+ calcd 349.3, found: 349.1.
In this study, a two benzyl naphthaimidazolium salts
(compound 3), an approximate “half open structure” of
compound 1, was designed and synthesized to further study the
mechanism. By the change of the substitutions in the 1,3-
position of imidazole, another two reference compounds 4 and
5, with one or two electropositive pentauoro-substituted
benzyl groups, were synthesized. (Scheme 2).
Synthesis of compound 3
Experimental
Under N2 gas, benzyl bromide (55 mL, 0.47 mmol) was added to
the solution of compound 11 (0.10 g, 0.39 mmol) in 15 mL
dioxane, which was heated to reux and kept for 24 h. Aer
cooling to room temperature, the yellowish precipitate was
collected by ltration and then washed with some cold CH2Cl2
to give the bromated. Then it was dissolved in DMF, and
dropped saturated KPF6 aqueous solution to precipitate the
product 3, which was puried by ash column chromatography
(CH2Cl2–CH3OH, 20 : 1, Rf ¼ 0.4) to give light gray white powder
(0.11 g, yield: 60%). 3: 1H NMR (400 MHz, CD3CN, d ppm) 9.19
(s, 1H), 8.31 (s, 2H), 8.10 (dd, J ¼ 6.4, 3.3 Hz, 2H), 7.64 (dd, J ¼
6.5, 3.2 Hz, 2H), 7.52 (dd, J ¼ 7.8, 1.5 Hz, 4H), 7.46 (m, J ¼ 7.2
Hz, 6H), 5.70 (s, 4H). 13C NMR (100 MHz, CD3CN, d ppm)
147.24, 134.37, 131.38, 130.64, 129.50, 129.22, 128.83, 128.71,
127.26, 111.90, 50.61. HRMS (TOF LD+) m/z [C25H21N2+] calcd
349.1699, found: 349.1728.
All chemicals were analytical pure and used without further
purication. 1H-NMR and 13C-NMR spectra were recorded on a
Bruker AV-400 spectrometer (TMS as an internal standard).
Mass spectrometry data were obtained with a HP1100LC/MSD
and MALDI micro MX mass spectrometer. Fluorescence
measurements were carried out on a JASCO FP-6500 uores-
cence spectrophotometer. Absorption spectra were collected on
a Hewlett-Packard HP-8453 UV-Vis spectrophotometer.
Synthesis of compound 8
Under N2 gas, 2,3-diaminonaphthalene (1.0 g, 6.3 mmol) was
dissolved in 10 mL formic acid. The solution was heated to
reux and kept for 5 h. Aer cooling to room temperature, the
mixture was concentrated to remove formic acid. The residue
was treated with 30 mL boiling water to dissolve, reuxed for 0.5
Synthesis of compound 4 and 5
h with some activated charcoal, and then ltered while hot and Starting from compound 12 (0.20 g, 0.57 mmol), compound 4
added stronger ammonia water to the ltrate dropwise until the (0.21 g, yield: 64%) and 5 (0.20 g, yield: 59%) were obtained
product precipitated completely. The grey white precipitate was according to the synthetic procedure of 3.
collected by ltration and then dried in a vacuum oven to give 8
Compound 4. 1H NMR (400 MHz, CD3CN, d ppm) 9.30 (s,
(0.75 g, yield: 71%). 1H NMR (400 MHz, CDCl3, d ppm): 8.20 (s, 1H), 8.36 (s, 1H), 8.32 (s, 1H), 8.22–8.17 (m, 1H), 8.13–8.08 (m,
1H), 8.09 (s, 2H), 7.95 (d, J ¼ 3.0 Hz, 2H), 7.41 (d, J ¼ 3.1 Hz, 2H), 1H), 7.71–7.64 (m, 2H), 7.52 (dd, J ¼ 7.7, 1.6 Hz, 2H), 7.47 (dd, J
3.10 (s, 1H). MS (ES API+): m/z [C11H8N2 + H]+ calcd 169.19, ¼ 10.4, 5.1 Hz, 3H), 5.83 (s, 2H), 5.72 (s, 2H). 13C NMR (100 MHz,
found: 169.1.
CD3CN, d ppm) 146.57, 133.56, 132.65, 132.54, 131.08, 30.26,
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 43746–43751 | 43747