The Intramolecular Electronic Interaction Regulated by Five-membered Heterocycle Spacer

doi:10.21203/rs.3.rs-283721/v1

PDF

Research Article

The Intramolecular Electronic Interaction Regulated by Five-membered Heterocycle Spacer

https://doi.org/10.21203/rs.3.rs-283721/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted 08 Mar, 2021

You are reading this latest preprint version

The spacer in diferrocenyl derivatives has significant effects on intramolecular electronic interaction properties. In this work, nine diferrocenyl five-membered heterocyclic molecules are synthesized as models to investigate the effect of intramolecular electron-transfer properties systematically, including 2,5-diferrocenyl-1-phenyl-pyrrole (1), 2,5-diferrocenylfuran (2), 2,5-diferrocenylthiophene (3), 2,5-diferrocenyl-1H-imidazole (4), 2,5-diferrocenyloxazole (5), 2,5-diferrocenylthiazole (6), 2,5-diferrocenyl-1,3,4-triazole (7), 2,5-diferrocenyl-1,3,4-oxadiazole (8) and 2,5-diferrocenyl-1,3,4-thiadiazole (9). The molecules were prepared in cyclization reaction and characterized by Elemental analysis, FT-IR, MS and NMR. Moreover, the molecular structures of 2,5-diferrocenylthiazole and 2,5-diferrocenyl-1,3,4-oxadiazole were determined by the single crystal X-ray diffraction. The intramolecular electronic interactions were investigated through cyclic voltammetry in combination with density functional theory (DFT) calculations. The results revealed that the electronic interaction decreased with the increase of heteroatoms in central heterocycle spacer, and the electron-transfer property could be regulated by regulate central heterocycle spacer species.

Chemical Engineering

diferrocenyl derivatives

intramolecular electronic interaction properties

central heterocycle spacer species

The ferrocene (Fc) is widely used in investigating the intramolecular electron transfers due to its redox activity and electrochemical stability, and the research on intramolecular electron transfers could provide simple and convenient for designing prospective ferrocene-containing molecular wires and conducting polymers^1-4. Generally, two or more ferrocenyl units assembled through various conducting spacers to construct molecular models for studying intramolecular electron transfers⁵, the various kind spacers involving of the atom⁶, alkenyl⁷, alkynyl⁸ and various aromatic rings⁹. When one of ferrocene unit occur electrochemical oxidize, an intramolecular donor-acceptor system is formed, the charge may be transfer to the other ferrocene units through the spacers, and the spacers’ types¹⁰, structures¹¹ and chemical properties¹² can influence the electron transfers capability. For example, when a single C atom spacer¹³ or a single N atom spacer¹⁴ link two-ferrocene units, the charge transfer capability of the C atom is better than that of the N atom. In addition, diferrocenyl derivatives containing π-conjugate spacers such as the alkenyl¹⁵ and alkynyl⁸, the electronic interaction capability of the alkenyl is better than that of the alkynyl. These electronic interaction properties can be associated with the atomic outer boundaries, ionization degree, and hybridization structure factors^16-18. However, when diferrocenyl derivatives containing aromatic rings spacers, the charge transfers are influenced by various complex factors, including metal-metal center distance¹⁹, position of substituent²⁰, center ring geometric properties²¹, topology²² and aromatic properties^23,24, which influencing factor is the primary factor of intramolecular electron transfer is still an academic debate. In order to further explore this problem, more and more researchers are engaged in numerous heterocycle spacers’ studies, especially the five-membered aromatic heterocycle spacers^25,26, because these spacers involves π-conjugate structure and heteroatom, which can provide changing chemical structure for studying.

In our research group previous works, the spacers’ charge density, properties of substituent and coplanarity of block connections were identified as key factors of intramolecular electron-transfers^27-30. In recent work, the single-heteroatom-five-membered-heterocycle bridged diferrocenyl derivatives were examined, which exhibited the charge transfer highly depend on the short-range heteroatom bridge^31,32, but this research had not systematically accomplished. One of inadequacies was the charge transfer properties on the central five-membered heterocycle spacer containing two and more heteroatoms were still unknown.

To reply the above-mentioned problem, a series of 2,5-diferrocenyl imidazole, oxazole, thiazole, triazole, oxadiazole and thiadiazole derivatives were synthesized as model molecules in this paper (Figure 1), and the intramolecular electron-transfers processes of these model molecules were systematically studied through cyclic voltammetry (CV) and density functional theory (DFT) calculations. The result revealed that the species and the numbers of heteroatom in central spacers could regulate intramolecular electronic transfer processes.

The molecular structures and the corresponding data of 1-3 are referenced form our academic paper³¹. The 4-9 were confirmed by FT-IR, ¹H-NMR, ¹³C-NMR, Elemental analysis, and MS (corresponding data are given in synthetic methods). The molecular structure of 6 and 8 were determined by single-crystal X-ray diffraction and shown in Figure S1 and Figure S2. Crystal data and relevant structural parameters enumerate in Table S1. The selected bond lengths, the selected angles and the selected torsion angles list in Table S2 and Table S3. The molecular structure of 9 is referenced form Heinrich Lang published academic paper³³.

Electrochemistry

The redox potential of compounds 1-9 is determined through cyclic voltammetry, and the electrochemical data is listed in Table 1. The compounds 1-6, 8 and 9 display two redox well-resolved waves in the range of 0-0.8 V (Figure 2-4), which are assigned to the two FeII/FeIII redox couples, from the Ipa/Ipc (≈1) values of each couple, it can be concluded that the redox processes are electrochemical reversible one-electron-transfer processes³¹. The 7 as an exceptional case display one redox well-resolved wave (Figure 2), and it is electrochemical reversible two-electron-transfer process³².

The first oxidation potentials (Ea₁) of ferrocenyl unit in 1-9 increase, with the increase of heteroatoms in central five-membered heterocycle spacer (Table 1). The Ea₁ of 1 is 58 mV and the Ea₁ of 4 is 138 mV, the Ea₁ of 7 even increase to 344 mV, with the central heterocycle form pyrrole change into imidazole and triazole. The Ea₁ of 2, 5 and 8 are 184 mV, 328 mV and 321 mV, respectively, the central heterocycle form furan change into oxazole and oxadiazole. The Ea₁ of 3, 6 and 9 are 217 mV, 304 mV and 308 mV, respectively, the central spacer form thiophene change into thiazole and thiadiazole. The π-conjugation effects of 3, 6 and 9 were investigated through comparing the dihedral angles to explore the Ea₁ changing trend. The two dihedral angles formed by cyclopentadiene planes to the central thiophene plane both are 8.93° of 3. The two dihedral angles formed by cyclopentadiene planes to the central thiazole plane of 6 are different, the one formed by plane S1-C6-N1-C7-C8 to C1-C2-C3-C4-C5 is 3.52°, the other formed by plane S1-C6-N1-C7-C8 to C9-C10-C16-C17-C18 is 5.30°. The two dihedral angles formed by cyclopentadiene planes to the central thiadiazole plane both are 17.08° of 9 (Figure S3). In theory, the smaller dihedral angle indicate more coplanarity between the cyclopentadienyl planes and the central plane, which suggests there are stronger π-conjugation effects with each other, and the Ea₁ should be lower³². Hence, the π-conjugation effect order is 6 > 3 > 9 indicate by dihedral angles, the order of Ea₁should be 6 (Ea₁=304 mV) < 3 (Ea₁=217 mV) < 9 (Ea₁=308 mV), but this result was disagreement with our experiment. Therefore, the embedded N atoms in 6 and 9 debase charge density of central heterocycle with its stronger electron withdrawing effects, and block the charge transfer between two ferrocenyl units.

The electronic communication effects of 1-9 were discussed through comparing the oxidation potential differences (∆E) with two ferrocenyl units. The ∆E of 1 is 315 mV, the ∆E of 4 is 210 mV. However, the 7 has only one redox wave, of which ∆E cannot be measured. The ∆E of 2 is 161 mV, the ∆E of 5 is 130 mV and the ∆E of 8 is 88 mV. Moreover, the ∆E of 3 is 139 mV, the ∆E of 6 is 124 mV and the ∆E of 9 is 86 mV (Table 1), respectively. Clearly, the values of ∆E are trending downward obviously, which exhibit the embedded N atoms in central spacers have debased electronic communication between two ferrocenyl units.

In general, the shorter distance of bimetal center indicated stronger electrostatic interaction and express larger ∆E^19,31. However, the order of Fe1-Fe2 distance is 1 (8.518 Å)> 6 (8.420 Å) > 9 (8.047 Å) > 3 (7.084 Å)> 2 (6.599 Å) > 8 (6.581 Å) measured from crystal structure (Figure S4), which is disagreement with the ∆E variation trend 9 (86 mV) < 8 (88 mV) < 6 (124 mV) < 3 (139 mV) < 2 (161 mV) <1 (315 mV) in our experiment. Hence, the electronic communication of 1-9 is not affected by the Fe-Fe distance.

The π-conjugation effect of ∆E was discussed by crystal structure data. The torsion angles Fe1-C1-C11-O1 (-80.05°) and Fe1′-C1′-C11′-O1 (80.05°) of 2³¹ are bigger than torsion angles O1-C13-14-Fe1 (-66.93°) and O1-C12-C9-Fe2 (73.20°) of 8 (Table S3), which express the π-conjugation effect of diferrocenyl and central spacer is stronger in 2 than in 8, the electronic communication is stronger in 2 (∆E=161 mV) than in 8 (∆E=88 mV). In theory, the stronger π-conjugation effects indicate the better electronic communication between two ferrocenyl units³². However, the π-conjugation effect deduced by torsion angles is 6 (Table S3) > 3³¹ > 9³³, the electronic communication order should be 6 (∆E=124 mV) > 3 (∆E=139 mV) > 9 (∆E=86 mV), but this result is not inagreement with our experiment, which indicates the embedded N atoms in central spacer is more important than π-conjugation effect for electronic communication.

NMR studies confirmed that the aromaticity of central spacers not affect electronic communication. The β-H chemical shifts of 1-6 are 6.383 ppm, 6.152 ppm, 6.806 ppm, 7.272 ppm, 6.941 ppm and 7.523 ppm (Figure S5-S10), respectively. Hence, the aromaticity order of centre heterocycle is 6 > 4 > 5 > 3 > 1 > 2. In theory, the central spacer bridge has stronger aromatic properties, and there is more strongly intermetallic electron transfer interaction^35,36. The order of ∆E value should be 6 > 4 > 5 > 3 > 1 > 2 according to aromaticity. However, this result is also not consistent with experiment. Furthermore, the NMR studies cannot be used in confirming the aromaticity of 7, 8 and 9, because there have no C-H bonds in central heterocycle. Consequently, the central spacers’ aromaticity confirmed by using the Nucleus Independent Chemical Shifts (NICS)^37,38. The NICS are -14.7369, -14.0069, -14.0642, -12.6821, -12.1474, -11.5493, -19.8319, -19.6180 and -20.4250 corresponding to pyrrole, imidazole, triazole, furan, oxazole, oxadiazole, thiophene, thiazole and thiadiazole, respectively. Hence, the aromaticity order is thiadiazole > thiophene > thiazole > pyrrole > triazole > imidazole > furan > oxazole > oxadiazole, and the ∆E order should be 9 > 3 > 6 > 1 > 7 > 4 > 2 > 5 > 8 deduce by NICS. However, it is not consistent with the ∆E variation trend 7 (none ∆E) < 9 (86 mV) < 8 (88 mV) < 6 (124 mV) < 5 (130 mV) < 3 (139 mV) < 2 (161 mV) < 4 (210 mV) < 1 (315 mV) in this work (Table 1). The NMR and NICS studies confirm that the aromaticity of the central spacers not affect the electronic communication.

The Natural Bond Orbital charge (NBO charge) population of heteroatom studies confirmed that electronic communication was highly affected by shorter heteroatom-linked bridge (Table 2). The NBO charges of N bridge in 1, 4 and 7 are -0.36285e, -0.54737e and -0.56883e; the NBO charges of O bridge in 2, 5 and 8 are -0.45454e, -0.46470e and -0.47372e; the NBO charges of S bridge in 3, 6 and 9 are 0.43772e, 0.40189e and 0.36804e, respectively. According to Allen electronegativity theory³⁹, the electronegativity values of C, N, O and S are 2.50, 3.07, 3.50 and 2.44 respectively. Therefore, the NBO charges of N and O atom are negative value; the NBO charge of S atom is positive value. Therefore, the embedded N atoms located in the 3,4-position of central spacer have stronger electron withdrawing effects to debase density of heterocyclic.

The shorter heteroatom-linked bridge NBO charge negative mobile made the electronic communication abated when molecules structure established by deliberately designed (Figure 5). The other atoms NBO charges in central spacer have no obvious relationship with electronic communication (Table S4). Hence, the electronic communication capacity was highly depend on shorter heteroatom-linked bridge NBO charge, this conclusion was consistent with our previous work³¹, and the shorter heteroatom-linked bridge NBO charges was influenced by the molecules structure of central heterocyclic. This work revealed that the electrochemical interaction receded with increase the heteroatom number in central heterocycle spacer, and the electronic interaction could be artificial regulated by modified molecular structure of central heterocycle spacer.

In conclusion, nine 2,5-diferrocenyl five-membered derivatives have been discussed deeply as the systematic electrochemical model. The results revealed electronic interaction had non-significant relationship with the distance of bimetal, π-conjugation effect and aromaticity of the central heterocyclic. The N atoms located in the 3,4-position of center heterocyclic could severe regulate the electronic transfer between two ferrocenyl units, and the intramolecular electronic interaction receded with the increase of heteroatom in centre heterocycle spacer.

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)hydrazine^41,42, ferrocenecarbonyl-hydrazine⁴³, N-(Ferrocenecarbonylmethyl)ferrocenecarboxamide⁴⁴, ferroceneamidine^45,46 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, ν_C-H]; 1612 cm^-1 [Cp, ν_C=C]; 1432 cm^-1 [C₃H₂N₂, ν_N=C]; 1414 cm^-1 [C₃H₂N₂, ν_C=C]; 1104, 1000 cm^-1 [Cp, δ_C-H]; 809 cm^-1 [Cp, γ_C-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, ν_C-H]; 1613 cm^-1 [Cp, ν_C=C]; 1588 cm^-1 [C₃HNO, ν_N=C]; 1409 cm^-1 [C₃HNO, ν_C=C]; 1105, 1001 cm^-1 [Cp, δ_C-H]; 815 cm^-1 [Cp, γ_C-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, ν_C-H]; 1543 cm^-1 [Cp, ν_C=C]; 1470 cm^-1 [C₃HNS, ν_N=C]; 1259 cm^-1 [C₃HNS, ν_C=C]; 1104, 1029 cm^-1 [Cp, δ_C-H]; 813 cm^-1 [Cp, γ_C-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, ν_C-H]; 1648 cm^-1 [Cp, ν_C=C]; 1471 cm^-1 [C₂HN₃, ν_N=C]; 1104, 1025 cm^-1 [Cp, δ_C-H]; 827 cm^-1 [Cp, γ_C-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, ν_C-H]; 1604 cm^-1 [Cp, ν_C=C]; 1579 cm^-1 [C₂N₂O, ν_O-C]; 1457 cm^-1 [C₂N₂O, ν_N=C]; 1104, 1025 cm^-1 [Cp, δ_C-H]; 809 cm^-1 [Cp, γ_C–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, ν_C-H]; 1572 cm^-1 [Cp, ν_C=C]; 1518 cm^-1 [C₂N₂S, ν_S-C]; 1410 cm^-1 [C₂N₂S, ν_N=C]; 1104, 1000 cm^-1 [Cp, δ_C-H]; 820 cm^-1 [Cp, γ_C-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%).

Acknowledgements (not compulsory)

We are grateful to the Natural Science Foundation of China (22065028), the Natural Science Foundation of Inner Mongolia (2017MS(LH)0202) and University Scientific research Foundation of Inner Mongolia (NJZY17102).

Author contributions statement

All authors reviewed the manuscript. Y.Q.H and L.M.H. conceived and designed the experiments. Y.Q.H and N.W. analyzed the data. Y.Q.H wrote the manuscript. Y.Q.H, L.M.H. and N.W. are involved in the related discussion. All authors reviewed the manuscript.

Competing Interests: The authors declare no competing interests.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and

institutional affiliations.

Ramandeep, K. et al. Understanding and Controlling Short- and Long-Range Electron/Charge-Transfer Processes in Electron Donor-Acceptor Conjugates. Am. Chem. Soc.142(17), 7898-7911, DOI: https://doi.org/10.1021/jacs.0c01452 (2020).
Albert, C. A. et al. Control over Near-Ballistic Electron Transport through Formation of Parallel Pathways in a Single-Molecule Wire. Am. Chem. Soc. 141(1), 240-250, DOI: https://doi.org/10.1021/jacs.8b09086 (2019).
Masayuki, N. Karin, S. et al. Intramolecular Electron Transfers in a Series of [Co₂Fe₂] Tetranuclear Complexes. Chem.58(18), 11912-11919, DOI: https://doi.org/10.1021/acs.inorgchem.9b00776 (2019).
Ke, Q. Shukkoor, M. K. Jian, L. et al. Carbohydrate-functionalized polythiophene biointerface: design, fabrication, characterization and application for protein analysis. Applied Surface Science.486, 561-570, DOI: https://doi.org/10.1016/j.apsusc.2019.04.231 (2019).
Kristina, H. Christoph, F. Katja, H. Redox-Controlled Stabilization of an Open-Shell Intermediate in a Bioinspired Enzyme Model. J. Inorg. Chem.31, 3537-3547, DOI: https://doi.org/10.1002/ejic.201800570 (2018).
My, P. T. C. Quail, J. W. et al. Enantiopure Ferrocenophanes with Phosphorus in Bridging Positions: Thermostability and Ring-Opening Polymerization. Organometallics. 38(9), 2092-2104, DOI: https://doi.org/10.1021/acs.organomet.9b00114 (2019).
Wang,Y. P. Lin, T. B. et al. 2D HETCOR NMR spectra and unequivocal assignments of (E)- and (Z)-1-ferrocenyl-2-phenylethene, and (1E,3E)- and (1Z,3E)-1-ferrocenyl-4-phenyl-1,3-butadiene, (E)-1,2-diferreocenylethene, and (1E,3E)-1,4-diferrocenyl-1,3-butadiene in ¹³C NMR spectra. Polyhedron. 127, 410-419, DOI: https://doi.org/10.1016/j.poly.2016.10.006 (2017).
Ma, J. X. Nico, K. et al. 1,1′-Dialkynylferrocenes as Substrates for Bidirectional Alkyne Metathesis Reaction. J. Org. Chem. 20, 4510-4518, DOI: https://doi.org/10.1002/ejoc.201500483 (2015).
Peng, H. Baokang, J. et al. Synthesis, electrochemistry and IR spectroelectrochemistry of bisferrocenyl bridged benzene derivates. Journal of Organometallic Chemistry. 697, 57-64, DOI: https://doi.org/10.1016/j.jorganchem.2011.10.019 (2012).
Eric, G. Bertrand, G. et al. Intramolecular Electron Transfers Thwart Bistability in a Pentanuclear Iron Complex. Inorganic Chemistry. 55(18), 9178-9186, DOI: https://doi.org/10.1021/acs.inorgchem.6b00791 (2016).
Han, W. X. Shi, Y. Z. et al. Synthesis and electrochemical, linear and third-order nonlinear optical properties of ferrocene-based D-π-A dyes as novel photoredox catalysts in photopolymerization under visible LED irradiations. Dyes and Pigments. 166, 140-148, DOI: https://doi.org/10.1016/j.dyepig.2019.03.023 (2019).
Rani, A. Michal, V. et al. Real-Time Detection of Redox Events in Molecular Junctions. Am. Chem. Soc. 136(6), 2674-2680, DOI: https://doi.org/10.1021/ja412668f (2014).
Xie, R. J. Han, L. M. et al. Molecular structure and electrochemistry of carbon-bridged diferrocenyl compounds. Coord. Chem. 63(10), 1700-1710, DOI: https://doi.org/10.1080/00958972.2010.487102 (2010).
Julio, A. Angel, E. K. Structural and pH Control on the Electronic Communication between Two Identical Ferrocene Sites. Organometallics. 18(26), 5733-5734, DOI: https://doi.org/10.1021/om990678r (1999).
Alessandro, D. Annalisa, B. et al. Electron transfer within C₄ unsaturated spacers between terminal ferrocenyl moieties. Inorganica Chimica Acta. 374(1), 442-446, DOI: https://doi.org/10.1016/j.ica.2011.03.014 (2011).
Victor, N. N. Semyon, V. D. et al. Probing Electronic Communications in Heterotrinuclear Fe-Ru-Fe Molecular Wires Formed by Ruthenium(II) Tetraphenylporphyrin and Isocyanoferrocene or 1,1′-Diisocyanoferrocene Ligands. Chem. 54(22), 10711-10724, DOI: https://doi.org/10.1021/acs.inorgchem.5b01614 (2015).
John, R. H. Yu, J. X. et al. Unraveling the Interplay of Backbone Rigidity and Electron Rich Side-Chains on Electron Transfer in Peptides: The Realization of Tunable Molecular Wires. Am. Chem. Soc. 136(35), 12479-12488, DOI: https://doi.org/10.1021/ja507175b (2014).
Yu, J. X. John, R. H. The effect of a macrocyclic constraint on electron transfer in helical peptides: A step towards tunable molecular wires. Commun. 50, 1652-1654, DOI: https://doi.org/10.1039/c3cc47885h (2014).
Alexander, H. Dieter, S. et al. Diferrocenes containing thiadiazole connectivities. Inorganica Chimica Acta. 374, 112-118, DOI: https://doi.org/10.1016/j.ica.2011.02.058 (2011).
Wang, Y. Q. Han, L. M. et al. Synthesis, structure and electrochemistry of new diferrocenyl pyridine derivatives. Polyhedron. 54, 221-227, DOI: https://doi.org/10.1016/j.poly.2013.02.043 (2013).
Huang, C. B. Huang, Y. F. et al. Cycloheptyl-fused N,N,N′-chromium catalysts with selectivity for vinyl-terminated polyethylene waxes: thermal optimization and polymer functionalization. Dalton Trans. 47, 13487-13497, DOI: https://doi.org/10.1039/C8DT03052A (2018).
Cendrine, P. Christophe, C. et al. Topological Effects on Intramolecular Electron Transfer via Quantum Interference. Chem. 36(22), 5037-5049, DOI: https://doi.org/10.1021/ic970013m (1997).
Rajneesh, M. Rekha, S. et al. Star shaped ferrocenyl truxenes: synthesis, structure and properties. Dalton Trans. 43, 6891-6896, DOI: https://doi.org/10.1039/C4DT00210E (2014).
James, R. W. Karl, J. S. et al. 3,5-Diferrocenylpyridine: Synthesis, characterisation, palladium(II) dichloride complex and electrochemistry. Polyhedron. 36, 73-78, DOI: https://doi.org/10.1016/j.poly.2012.01.028 (2012).
Ritu, S. Dhara, P. et al. A mini review: recent developments of heterocyclic chemistry in some drug discovery scaffolds synthesis. Journal of Medicinal and Chemical Sciences. 3(1), 71-78, DOI: 26655/JMCHEMSCI.2020.1.9 (2020).
Tauchman, J. Jakub, T. et al. Synthesis, crystal structures and electrochemistry of ferrocenyl-substituted 1,3,4-oxadiazoles. Czech. Chem. Commun. 75, 1023-1040, DOI: 10.1135/cccc2010064 (2010).
Liu, Z. S. Zhu, N. et al. Detecting the electron density of benzene using ferrocene as an indicator. Coord. Chem. 65(16), 2804-2810, DOI: https://doi.org/10.1080/00958972.2012.704024 (2012).
Xie, R. J. Han, L. M. et al. An effective method for the synthesis of monoferrocenylbenzene derivatives. Coord. Chem. 65(23), 4086-4095, DOI: https://doi.org/10.1080/00958972.2012.732696 (2012).
Xie, R. J. Han, L. M. et al. The effect of acetyl on the electronic communication of carbon-bridged diferrocene. Coord. Chem. 64(18), 3180-3188, DOI: https://doi.org/10.1080/00958972.2011.616198 (2011).
Xie, R. J. Han, L. M. et al. Synthesis of ortho-diferrocenylbenzene with cobalt clusters as reaction precursors: Crystal structure and electrochemical properties. Polyhedron. 38(1), 7-14, DOI: https://doi.org/10.1016/j.poly.2012.02.018 (2012).
Hu, Y. Q. Han, L. M. et al. Synthesis of 2,5-diferrocenyl five-membered heterocyclic compounds and their electrochemistry. Coord. Chem. 66(19), 3481-3497, DOI: https://doi.org/10.1080/00958972.2013.841902 (2013).
Hu, Y. Q. Zhu, N. et al. Channel of Electronic Interactions in Diferrocenyl Pyrrole Derivatives. Acta Physico-Chimica Sinica. 31(2), 227-236, DOI: 3866/PKU.WHXB201411061 (2015).
Alexander, H. Dieter, S. et al. Diferrocenes containing thiadiazole connectivities. Inorganica Chimica Acta. 374(1), 112-118, DOI: https://doi.org/10.1016/j.ica.2011.02.058 (2011).
Smith, M. B. March, J. March’s Advanced Organic Chemistry. 2, 54, DOI: https://doi.org/10.1002/9780470084960.ch2 (2007).
Luo, M. H. Han, L. M. et al. Synthesis and structural characterization of ferrocenyl indenyl derivatives. Coord. Chem. 63(21), 3805-3815, DOI: https://doi.org/10.1080/00958972.2010.521937 (2010).
Cendrine, P. Christophe, C. et al. Topological Effects on Intramolecular Electron Transfer via Quantum Interference. Inorganic Chemistry. 36(22), 5037-5049, DOI: https://doi.org/10.1021/ic970013m (1997).
Chemical Bonding and Aromaticity in Furan, Pyrrole, and Thiophene: A Magnetic Shielding Study. Journal of Organic Chemistry. 78(16), 8037-8043, DOI: https://doi.org/10.1021/jo401319k (2013).
Kate, E. H. Peter, B. K. Shielding in and around Oxazole, Imidazole, and Thiazole: How Does the Second Heteroatom Affect Aromaticity and Bonding? Journal of Organic Chemistry. 80(14), 7150-7157, DOI: https://doi.org/10.1021/acs.joc.5b01010 (2015).
Leland, C. A. Electronegativity is the average one-electron energy of the valence-shell electrons in ground-state free atoms. Journal of the American Chemical Society. 111(25), 9003-9014, DOI: https://doi.org/10.1021/ja00207a003 (1989).
Alberto, T. Pedro, M. et al. Aza-wittig reactions of iminophosphoranes derived from ferrocenylazido ketones: preparation and electrochemical study of novel ferrocenyl-substituted azaheterocycles. Tetrahedron. 55(51), 14701-14718, DOI: https://doi.org/10.1016/S0040-4020(99)00916-3 (1999).
Raspopova, E. A. Popov, L. D. et al. Synthesis, structure, and complexing ability of pyrrole-2-carbaldehyde ferrocenoylhydrazone. Russian Journal of General Chemistry. 78(8), 1586-1593, DOI: https://doi.org/10.1134/S1070363208080215 (2008).
Gabin, M. M. Jouda, J. et al. Synthesis and antimycobacterial activity of a series of ferrocenyl derivatives. European Journal of Medicinal Chemistry. 46(1), 31-38, DOI: https://doi.org/10.1016/j.ejmech.2010.10.004 (2010).
Petr, S. Ivana, C. et al. The crystal structures, molecular spectra and thermal behaviour of carbamoylferrocene and ferrocenecarbonylhydrazide. Polyhedron. 29(1), 134-141, DOI: https://doi.org/10.1016/j.poly.2009.06.034 (2010).
Alberto, T. Pedro, M. et al. Synthesis of the first homobimetallic thiazole–ferrocene ligand displaying metal–metal interaction and redox-switchable proton affinity. Tetrahedron Letters. 43(47), 8453-8457, DOI: https://doi.org/10.1016/S0040-4039(02)02097-X (2002).
Zhang, P. T. Yang, X. Y. et al. Pyridinylpyrimidines selectively inhibit human methionine aminopeptidase-1. Bioorganic & Medicinal Chemistry. 21(9), 2600-2617, DOI: https://doi.org/10.1016/j.bmc.2013.02.023 (2013).
Omid, K. A. Nader, S. et al. Synthesis of a series of carbon‐14 labeled tetrahydropyrido[4,3-d]pyrimidin-4(3H)-ones. Journal of Labelled Compounds and Radiopharmaceuticals. 56(14), 722-725, DOI: https://doi.org/10.1002/jlcr.3110 (2013).
Ma, J. Cui, X. L. et al. Ferrocenylimidazoline palladacycles: efficient phosphine-free catalysts for Suzuki-Miyaura cross-

No competing interests reported.

SupportingInformation.docx
Additional information Crystallographic data for the structural analysis have been deposited at the Cambridge Crystallographic Data Centre, CCDC No. 1536574 and 1431129 for 6 and 8 respectively. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: t44-1223-336033; Email: [email protected]).

PDF

Version 1

posted 08 Mar, 2021

You are reading this latest preprint version

The Intramolecular Electronic Interaction Regulated by Five-membered Heterocycle Spacer

Status:

Version 1

Abstract

Figures

Introduction

Results And Discussion

Methods

Declarations

Acknowledgements (not compulsory)

Author contributions statement

References

Additional Declarations

Supplementary Files

Status:

Version 1