Theoretical Study and Structural Relationships of Free Energies of Electron Transfer, Electrochemical Properties and Electron Transfer Kinetics of Ferrocene Derivatives with Fullerenes in Nanostructures of [(R)₂Cp₂-Fe].C_n Supramolecular Complexes

Abstract

Ferrocene (Cp₂-Fe) and its derivatives are part of a broad-spectrum of organometallic compounds that are commonly used in electronics and semiconductors. Fullerenes are a family of carbon allotropes composed entirely of carbon in the form of spheres, ellipsoids and cylinders. Various empty carbon fullerenes (C_n) have been obtained and investigated. The Cp₂-Fe derivatives have exhibited important electron-transfer properties. Topological indices have been proposed to correlate structures with properties. They have been successfully employed to construct effective and useful mathematical methods to establish clear relationships between structural data and the physical properties of these materials. In this study, the number of carbon atoms in the fullerenes was used as an index to establish a relationship between the structures of ferrocenyl derivatives (1–15), ferrocenyl fullerene complexes 1–15 (the most well-known redox systems) and fullerenes C_n (n = 60, 70, 76, 82 and 86) A-1 to O-5, which are commonly denoted as [Fc-x].C_n. The Rehm-Weller equation was applied to build the relationship between the structures and the free energies for electron transfer (ΔG_et(1) to ΔG_et(4) ) of the complexes [Fc-x].C_n (A-1 to O-5). The calculations are presented for the four reduction potentials ( ^Red.E₁ to ^Red.E₄ ) of the fullerenes C_n . The reduction potentials of the fullerenes C_n have been applied to calculate the four free energies of electron transfer (ΔG_et(1) to ΔG_et(4) ) of supramolecular complexes [Fc-x].Cn (A-1 to O-5). Based on Marcus theory and Planck's equation, the first four free activation energies of electron transfer and the wavelengths (ΔG_et(1) ^# to ΔG_et(4) ^# and λ _et , n = 1–4, respectively) for the photoelectron transfer process were also calculated for [Fc-x].Cn (A-1 to O-5).

Keywords:

• Fullerenes
• ferrocenes
• Rehm-Weller equation
• free energy of electron transfer
• electron transfer properties
• activated free energies of electron transfer
• kinetic constant of electron transfer
• Marcus theory
• molecular modeling

Acknowledgments

The corresponding author gratefully acknowledges colleagues in the Chemistry Department of The University of Queensland (UQ) and the Chemistry Department of The University of New England (UNE)-Australia for their useful suggestions.