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. 2019 Oct 18;5(10):e02580.
doi: 10.1016/j.heliyon.2019.e02580. eCollection 2019 Oct.

Synthesis, crystal structures and electrochemical properties of ferrocenyl imidazole derivatives

Ayomide H Labulo  1 , Bernard Omondi  1 , Vincent O Nyamori  1
Affiliations

Synthesis, crystal structures and electrochemical properties of ferrocenyl imidazole derivatives

Ayomide H Labulo et al. Heliyon. .

Abstract

Six ferrocenyl imidazole derivatives substituted with -Cl, -NO2 and -CH3 on the 2-position of the 1H-imidazole ring have been synthesized. Of the six compounds, the di-substituted ferrocenes, i.e. compounds 4 (1,1'-ferrocenylmethyl(2-chloroimidazole)), 5 (1,1'-ferrocenyl(2-nitroimidazole)), and 6 (1,1'-ferrocenylmethyl(2-methylimidazole)) are reported for the first time. The structure-property relationships of compounds 4, 5 and 6 were investigated by means of UV-visible, FTIR, 1H-NMR, 13C-NMR spectroscopy and electrochemical studies. UV-visible analysis in acetonitrile showed that the π -π* band of compounds 2 (1-ferrocenylmethyl(2-nitroimidazole)) and 5 appeared at longer wavelength compared to 1 (1-ferrocenylmethyl(2-chloroimidazole)), 3 (1-ferrocenylmethyl(2-methylimidazole)), 4 and 6. This phenomenon is due to the different electronics around the imidazole moieties. In cyclic voltammetry analysis, all compounds exhibited a quasi-reversible redox wave for the ferrocenyl and imidazole moieties. Density functional theoretical (DFT) calculations with the B3LYP/6-311+G(d) basis set were performed on compounds 1-6, and the calculated HUMO-LUMO band gap energies correlated with those obtained from electrochemical and spectroscopic data. The X-ray crystallographic analysis highlighted the effect of electron-withdrawing and electron-donating substituents on the conformation of the cyclopentadienyl rings attached to the ferrocenyl moiety.

Keywords: Cyclic voltammetry; DFT calculations; Ferrocenyl imidazole derivatives; Materials chemistry; Theoretical chemistry; UV-vis spectroscopy.

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Figures

Scheme 1
Scheme 1
Reaction schemes of (a) ferrocenemethanol and (b) 1,1′-diferrocenemethanol for the synthesis of compounds 1–6.
Fig. 1
Fig. 1
1H-NMR of compounds (a) 4 (b) 5 and (c) 6.
Fig. 2
Fig. 2
13C-NMR of compounds (a) 4 (b) 5 and (c) 6.
Fig. 3
Fig. 3
ORTEP diagrams, along with the atom-numbering scheme for compounds (a) 4 and (b) 5. The thermal ellipsoids are depicted at 50% probability.
Fig. 4
Fig. 4
UV-visible spectra of 0.005M solutions of 1-6 in acetonitrile.
Fig. 5
Fig. 5
UV-visible spectra of 0.005 M solutions of compound 1 in DMF, acetonitrile, methanol and DCM.
Fig. 6
Fig. 6
Cyclic voltammogram of compounds (a) 1–3 and (b) 4–6 in 0.5 M NaClO4/acetonitrile at a platinum working electrode.
Fig. 7
Fig. 7
Lobes of the frontier molecular orbitals for the symmetric compound 5 obtained from the M1 theoretical model.
See this image and copyright information in PMC

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