Synthesis of 2,5-diferrocenyl five-membered heterocyclic compounds and their electrochemistry

Abstract

A series of 2,5-diferrocenyl substituted five-membered heterocyclic compounds, 2,5-diferrocenyl-1-phenylpyrrole (1), 2,5-diferrocenyl-1-(4-fluorophenyl)-pyrrole (2), 2,5-diferrocenyl-1-(4-ethoxyphenyl)-pyrrole (3), 2,5-diferrocenyl-1-(4-ethylphenyl)-pyrrole (4), 2,5-diferrocenylthiophene (5), and 2,5-diferrocenylfuran (6), were synthesized using one-pot cycloaddition of ferrocenyl alkyne and characterized by elemental analysis, FT-IR, MS, and NMR. The molecular structures of 1, 2, 5, and 6 were determined using single-crystal X-ray diffraction. Electronic communication between two ferrocenyl units of 1-6 was investigated using cyclic voltammetry. These compounds have two well-resolved electrochemically reversible one-electron-transfer processes using [NBu 4 ] [PF 6 ] as the supporting electrolyte. The electrochemical studies reveal that electronic communication between two ferrocenyl units depend on the heteroatoms.

The Intramolecular Electronic Interaction Regulated by Five-membered Heterocycle Spacer

“…The molecular structures and the corresponding data of 1-3 are referenced form our academic paper 31 .…”

“…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) > (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) < (139 mV) < 2 (161 mV) <1 (315 mV) in our experiment.…”

“…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 oneelectron-transfer processes 31 . The 7 as an exceptional case display one redox well-resolved wave ( Figure 2), and it is electrochemical reversible two-electron-transfer process 32 .…”

“…In our research group previous works, the spacers' charge density, properties of substituent and coplanarity of block connections were identi ed as key factors of intramolecular electron-transfers 27-30 . In recent work, the single-heteroatom-ve-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 ve-membered heterocycle spacer containing two and more heteroatoms were still unknown.…”

Synthesis of tetraferrocenylbenzene by cycloaddition reaction with alkyl cobalt clusters as reaction precursors

“…The first oxidation potential of 1 (410 mV) is lower than 2 (476 mV), illustrating that trimethylsilyl has stronger electron-donating effects [28,29]. The electronic communication effect of 1 and 2 was discussed through comparing the half-wave potential differences Tetraferrocenylbenzene 455 (ΔE 1/2 ) between ferrocenyl units.…”