Materials
4-Bromonaphthalene-1-carbonitrile, hydrazine hydrate, 2-methoxyethanol, 3-methyl-2-butanone, 3-aminophenol, 1-bromo-3-chloropropane, N,N-dimethylformamide, acetic ether, petroleum ether, dichloromethane, anhydrous ethanol, dimethyl sulfoxide, NaHCO3, POCl3, K2CO3, Na2SO4, NaF, NaCl, NaBr, NaI, NaHSO3, NaOH, KCl, CaCl2, AlCl3, ZnCl2, SnCl2, Pb(NO3)2, CuCl, CuCl2, FeCl2, FeCl3, MgCl2, AgCl, Ni(NO3)2, MnCl2, Na3PO4, Na2HPO4, NaH2PO4, Co(NO3)2, Cd(NO3)2, Na2CO3, NaBF4, NaI, NaN3, Na2C2O4, NaNO2, NaSCN, NaNO3, NaHSO4, Ala, Arg, Asp, Cys, Hcy, Gln, Glu, Gly, His, IIe, Leu, Met, Phe, Pro, Ser, Urea, Val.
Laboratory apparatus
Dual-beam UV-vis Spectrophotometer (TU-1901), Fluorospectrophotometer (F-4600), 400 M NMR spectrometer (AVIII HD 400), High-resolution mass spectrometer (IonSpec4.7), pH meter (PHS-2F), Rotary evaporator (RE-2000B), Electronic analytical balance (FA2004), Constant temperature magnetic stirrer (85 − 2), Vacuum drying oven (DZF-6020), Circulating water vacuum pump (SHB-3), Vacuum oil pump (2XZ-4), Digital camera (D3300), Portable UV analyzer (ZF-5).
The parameters of the solution in spectral tests
Configure the PBI with concentration of 1×10− 3 mol/L (dissolved in DMSO). Remove 30 µL of PBI solution and add it to 3000 µL solution containing 2400 µL PBS and 600 µL DMSO, the final concentration of PBI in the test system was 1×10− 5 mol/L.
The concentrations of anion ions, metal ions and small biomolecules used in the detection were 0.01 mol/L initially. The concentration of HSO3− was 0.05 mol/L.
Synthesis and methods
The synthetic route was shown in Scheme 1. Compound 3 was prepared according to previously reported method [39].
Synthesis of compound 1
4-Bromonaphthalene-1-carbonitrile (692.9 mg, 3 mmol) was dissolved in a mixed solution of hydrazine hydrate 80% (1.5 mL, 30 mmol) and 2-Methoxyethanol (25 mL), the resulting mixture was then heated to 125°C, and reacted under reflux for 8 h. After that, the solution was cooled, filtered with suction, and washed with ethanol to obtain the compound 1 (440 mg, 72.8%). 1H NMR (600 MHz, DMSO-d6): δH 8.57 (d, J = 8.2 Hz, 1H), 8.41 (s, 1H), 8.16 (d, J = 8.0 Hz, 1H), 7.84–7.74 (m, 2H), 2.43 (s, 3H), 1.38 (s, 6H). 13C NMR (151 MHz, DMSO-d6): δC 195.00, 152.79, 142.04, 133.14, 129.18, 128.26, 127.97, 125.92, 125.07, 124.41, 118.76, 105.43, 55.75, 22.10, 16.19.
Synthesis of compound 2
Compound 1 (402.75 mg, 2.2 mmol) was added to 3-methyl-2-butanone (20 mL), then concentrated sulfuric acid (0.5 mL) was mixed to get a white turbid liquid. The mixture was heated up to 125°C and reacted for 8 h. After the reaction, the mixture was cooled to room temperature, a solid precipitated out, and suction filtration to get the compound 2 (310 mg, 60.2%). 1H NMR (400 MHz, DMSO-d6): δH 8.61 (s, 1H), 8.26 (d, J = 8.5 Hz, 1H), 7.90 (dd, J = 19.5, 8.2 Hz, 2H), 7.71–7.63 (m, 1H), 7.55–7.46 (m, 1H), 7.07 (d, J = 8.3 Hz, 1H), 4.48 (s, 2H). 13C NMR (151 MHz, DMSO-d6): δC 151.91, 135.49, 133.43, 128.93, 125.62, 124.84, 122.86, 120.78, 120.27, 102.89, 93.4.
Synthesis of PBI
Compound 2 (217.11 mg, 1 mmol) and compound 3 (234.11 mg, 1 mmol) were dissolved in ethanol (30 mL), and the reaction mixture was heated to reflux for 12 h. Then the resulting mixture was cooled to room temperature and the product was collected by suction, washed with ethanol, and dried in vacuo (207.9 mg, 48.0%). 1H NMR (400 MHz, DMSO-d6): δH 8.64 (d, J = 7.7 Hz, 1H), 8.55 (s, 1H), 8.39 (s, 1H), 8.14 (d, J = 7.9 Hz, 1H), 7.94–7.73 (m, 2H), 7.52 (s, 1H), 7.00–6.85 (m, 1H), 3.37 (s, 5H), 2.77–2.55 (m, 4H), 1.89 (s, 4H), 1.57 (s, 6H). 13C NMR (151 MHz, DMSO-d6): δC 133.37, 129.58, 127.98, 125.24, 124.38, 118.99, 103.25, 50.03, 27.15, 25.10, 21.59, 21.24, 20.59, 15.61, 0.57.