Materials
All operations were carried out in an atmosphere of purified argon. All solvents were dried and distilled according to standard procedures. The reactions were monitored by thin-layer chromatography (TLC). 2-bromoacetyl-ferrocene40, 1,2-bis(ferrocenecarbonyl)hydrazine41,42, ferrocenecarbonyl-hydrazine43, N-(Ferrocenecarbonylmethyl)ferrocenecarboxamide44, ferroceneamidine45,46 and cyanoferrocene47 were prepared according to literature methods, and the solvents were commercially available. The 1-3 synthetic method have been report in our previous work31. The 4-9 were synthesized through cyclization reaction and the schematic preparation procedure of compounds (Figure 6) and characterization data are summarized in synthetic methods.
Characterization methods.
Cyclic voltammetry was performed on a platinum disk electrode in a dichloromethane solution of 1-9 with tetra-n-butylammonium hexafluorophosphate [NBu4] [PF6] (0.1 M) as the supporting electrolyte, at a scan rate of 100 mV s-1. The reference electrode was an Ag/Ag+ electrode and the auxiliary electrode was a coiled platinum wire. Oxygen was purged from the one-compartment cell before each electrochemical run. The geometry optimizations and DFT calculations of 1-9 were undertaken using the B3LYP functional and 6-31G* basis set combination.
Synthetic methods.
2,5-diferrocenyl-1H-imidazole (4): Ferroceneamidine (120.1 mg, 0.53 mmol), 2-bromoacetyl-ferrocene (200.5 mg, 0.65 mmol), K2CO3 (75.1 mg, 0.57 mmol) and THF (25 ml) were added to a shrek reactor under atmosphere of pure argon stirred at 90 °C for 24 h. The reaction solution was cooled to room temperature, the solvent removed in vacuo, and the residue was subjected to chromatographic separation on a silica gel column (2.0×30 cm) using a mixture of dichloromethane/petroleum ether (1/1, v/v) to elute the product at room temperature. The first orange band was unreacted 2-bromoacetyl-ferrocene. The second orange band was compound 4 (120.2 mg). Yield: 27.5%, m.p. 218-220 °C. Anal. Calcd for C23H20N2Fe2: C, 63.34; H, 4.62; N, 6.42. Found: C, 63.77; H, 4.71; N, 7.01%. IR (KBr disk): 3083 cm-1 [Cp, νC-H]; 1612 cm-1 [Cp, νC=C]; 1432 cm-1 [C3H2N2, νN=C]; 1414 cm-1 [C3H2N2, νC=C]; 1104, 1000 cm-1 [Cp, δC-H]; 809 cm-1 [Cp, γC-H]. 1H-NMR (CDCl3, δ): 12.48 (s, 1H, C3H2N2), 7.27 (s, 1H, C3H2N2), 4.25-4.72 (m, 18H, Cp). 13C-NMR (CDCl3, δ): 161.32, 161.15 (Ci-C3H2N2), 117.39 (C3H2N2), 77.26, 77.00, 76.75, 70.61, 70.45, 69.56, 69.35, 69.17, 68.05 (Cp). MS (ESI, relative abundance): 437.1 (M+1+, 100%).
2,5-diferrocenyloxazole (5): N-(Ferrocenecarbonylmethyl)ferrocenecarboxamide (223.2 mg, 0.5 mmol) and pyridine (20 ml) were a shrek reactor in atmosphere of pure argon stirred at 0 °C for 0.5 h, then POCl3 (0.5 ml, 5.0 mmol) was added to reactor stirred at room temperature (20 °C for 12 h. The reaction solution poured into crushed ice, then the solvent and the precipitate extracted by ethyl acetate (15 ml×3), and then the organic phase removed in vacuo. And the residue was subjected to chromatographic separation on silica gel column (2.0×30 cm) using a mixture of dichloromethane/petroleum ether (1/1, v/v) to elute the product at room temperature. The first orange band was compound 5 (131.6 mg). Yield: 59.9%, m.p. 158-160 °C. Anal. Calcd for C23H20NOFe2: C, 63.20; H, 4.38; N, 3.20. Found: C, 63.54; H, 4.11; N, 3.51%. IR (KBr disk): 3098 cm-1 [Cp, νC-H]; 1613 cm-1 [Cp, νC=C]; 1588 cm-1 [C3HNO, νN=C]; 1409 cm-1 [C3HNO, νC=C]; 1105, 1001 cm-1 [Cp, δC-H]; 815 cm-1 [Cp, γC-H]. 1H-NMR (CDCl3, δ): 6.94 (s, 1H, C3HNO), 4.17-4.96 (m, 18H, Cp). 13C-NMR (CDCl3, δ): 162.18, 150.16 (Ci-C3HNO), 122.18 (C3HNO), 77.29, 77.04, 76.78, 69.63, 69.28, 68.67, 67.77, 66.40, 66.38, 65.70 (Cp). MS (ESI, relative abundance): 437.1 (M+, 100%).
2,5-diferrocenylthiazole (6): N-(Ferrocenecarbonylmethyl)ferrocenecarboxamide (222.8 mg, 0.5 mmol), lawessons reagent (244.1 mg, 0.6 mmol) and THF (20 ml) were added to a shrek reactor in atmosphere of pure argon stirred at 80 °C for 12h. The reaction solution was cooled to room temperature, then the solvent removed in vacuo, and the residue was subjected to chromatographic separation on silica gel column (2.0×30 cm) using a mixture of dichloromethane/petroleum ether (1/1, v/v) to elute the product at room temperature. The first orange band was compound 6 (177.0 mg). The single crystal of 6 was obtained through recrystallizing from hexane/dichloromethane (4/1, v/v) at low temperature (-15 °C). Yield: 78.1%, m.p. 221-223 °C. Anal. Calcd for C23H20NSFe2: C, 60.96; H, 4.23; N, 3.09. Found: C, 59.54; H, 4.61; N, 3.52%. IR (KBr disk): 3090 cm-1 [Cp, νC-H]; 1543 cm-1 [Cp, νC=C]; 1470 cm-1 [C3HNS, νN=C]; 1259 cm-1 [C3HNS, νC=C]; 1104, 1029 cm-1 [Cp, δC-H]; 813 cm-1 [Cp, γC-H]. 1H-NMR (CDCl3, δ): 7.52 (m, 1H, C3HNS), 4.14-4.88 (m, 18H, Cp). 13C-NMR (CDCl3, δ): 162.82, 136.51 (Ci-C3HNS), 137.59 (C3HNS), 77.27, 77.02, 77.76, 71.22, 71.06, 70.25, 70.07, 69.96, 69.31, 68.74, 68.00, 66.72 (Cp). MS (ESI, relative abundance): 453.0 (M+, 100%).
2,5-diferrocenyl-1,3,4-triazole (7): Cyanoferrocene (211.1 mg, 1.0 mmol), sodium methoxide (216.3 mg, 4.0 mmol) and methanol (20 ml) were added to a shrek reactor in atmosphere of pure argon stirred at 75 °C for 24 h, and then ferrocenecarbonyl-hydrazine (244.2 mg, 1.0 mmol) was added to reactor stirred at 75 °C for 24 h. The reaction solution was poured into crushed ice, then the solvent and the precipitate were extracted by ethyl acetate (25 ml×5), and then the organic phase was removed in vacuo. And the residue was subjected to chromatographic separation on silica gel column (2.0×20 cm) using a mixture of dichloromethane/petroleum ether (1/1, v/v) to elute the product at room temperature. The first yellow band was unreacted cyanoferrocene. The second orange band was compound 7 (301.2 mg). Yield: 68.8%, m.p. 194-196 °C Anal. Calcd for C22H19N3Fe2: C, 60.45; H, 4.38; N, 9.61. Found: C, 61.07; H, 4.79; N, 10.01%. IR (KBr disk): 3111 cm-1 [Cp, νC-H]; 1648 cm-1 [Cp, νC=C]; 1471 cm-1 [C2HN3, νN=C]; 1104, 1025 cm-1 [Cp, δC-H]; 827 cm-1 [Cp, γC-H]. 1H-NMR (CDCl3, δ): 12.11 (s, 1H, C2HN3), 4.89-4.33 (m, 18H, Cp). 13C-NMR (CDCl3, δ): 173.58 (Ci-C2HN2), 71.31, 71.82, 71.80, 71.19, 71.17, 70.99, 7.041, 70.09, 69.80, 69.70, 68.85 (Cp). MS (ESI, relative abundance): 437.1 (M+, 100%).
2,5-diferrocenyl-1,3,4-oxadiazole (8): 1,2-bis(ferrocenecarbonyl)hydrazine (228.1 mg, 0.5 mmol) and pyridine (20 ml) were added to a shrek reactor in atmosphere of pure argon stirred at 0 °C for 0.5 h, then POCl3 (0.5 ml, 5.0 mmol) was added to reactor stirred at room temperature (20 °C) for 12 h. The reaction solution was poured into crushed ice, then the solvent and the precipitate were extracted by ethyl acetate (20 ml×3), and then the organic phase was removed in vacuo. And the residue was subjected to chromatographic separation on silica gel column (2.0×20 cm) using a mixture of dichloromethane/petroleum ether (1/1, v/v) to elute the product at room temperature. The first orange band was compound 8 (155.4 mg), and the single crystal of 8 was obtained through recrystallizing from hexane/dichloromethane (4/1, v/v) at low temperature (-15 °C). Yield: 70.7%, m.p. 216-219 °C. Anal. Calcd for C22H18N2OFe2: C, 60.32; H, 4.14; N, 6.39. Found: C, 60.64; H, 4.46; N, 6.77%. IR (KBr disk): 3111 cm-1 [Cp, νC-H]; 1604 cm-1 [Cp, νC=C]; 1579 cm-1 [C2N2O, νO-C]; 1457 cm-1 [C2N2O, νN=C]; 1104, 1025 cm-1 [Cp, δC-H]; 809 cm-1 [Cp, γC–H]. 1H-NMR (CDCl3, δ): 5.00-4.21 (m, 18H, Cp). 13C-NMR (CDCl3, δ): 165.97 (Ci-C2N2O), 77.33, 77.08, 76.82, 70.70, 69.84, 67.97, 66.89 (Cp). MS (ESI, relative abundance): 438.0 (M+, 100%).
2,5-diferrocenyl-1,3,4-thiadiazole (9): 1,2-bis(ferrocenecarbonyl)hydrazine (228.0 mg, 0.5 mmol), lawessons reagent (244.3 mg, 0.6 mmol) and THF (20 ml) were added to a shrek reactor under atmosphere of pure argon stirred at 80 °C for 12 h. The reaction solution was cooled to room temperature, then the solvent was removed in vacuo, and the residue was subjected to chromatographic separation on silica gel column (2.0×20 cm) using a mixture of dichloromethane/petroleum ether (1/1, v/v) to elute the product at room temperature.. The first orange band was compound 9 (189.0 mg). The single crystal of 9 was obtained through recrystallizing from hexane/dichloromethane (4/1, v/v) at low temperature (-15 °C). Yield: 83.2%, m.p. 206-212 °C Anal. Calcd for C22H18N2SFe2: C, 58.18; H, 3.99; N, 6.17. Found: C, 59.22; H, 4.22; N, 6.55%. IR (KBr disk): 3093 cm-1 [Cp, νC-H]; 1572 cm-1 [Cp, νC=C]; 1518 cm-1 [C2N2S, νS-C]; 1410 cm-1 [C2N2S, νN=C]; 1104, 1000 cm-1 [Cp, δC-H]; 820 cm-1 [Cp, γC-H]. 1H-NMR (CDCl3, δ): 5.00-4.18 (m, 18H, Cp). 13C-NMR (CDCl3, δ): 167.75, 165.95 (Ci-C2N2S), 77.28, 77.03, 76.78, 74.08, 70.68, 70.58, 70.34, 69.82, 68.89, 67.96, 66.87 (Cp). MS (ESI, relative abundance): 454.0 (M+, 100%).