DFT charge transfer of hybrid molecular ferrocene/Si structures

Abstract

The electrochemical behavior and electronic properties of redox-active ferrocenes grafted onto semiconductor Si(100) substrate were investigated theoretically by first-principles calculations. Organic molecules were attached via the formation of Si-C covalent bonds through two different linkers: vinyl (direct grafting), and N 3 (CH 2 ) 11 (indirect grafting). Redox energies and the electronic properties relating to different spacers in hybrid ferrocene Fc/Si and ferrocenium Fc + / Si structures were theoretically extracted and compared with experimental cyclic voltametry data. Electronic charge transfers are discussed through the alignment positions of the frontier orbitals of the molecule with respect to the Si substrate gap. Periodic boundary conditions were used to investigate the Si(100) as a slab surface and hybrid Fc/Si structures. The resulting projected density of states (PDOS) were compared with molecular results and discussed in the light of experimental data.

Redox-Active Ferrocene grafted on H-Terminated Si(111): Electrochemical Characterization of the Charge Transport Mechanism and Dynamics

“…From the experimental point of view, our electrochemical experimental results are in line with the evidence reported by Simonet 52 , Zannoni et al . 41,49 and Calborean 21 , when dealing with similar hybrid interfaces. The striking result is that the connection of the iron redox couple via a chain of single (N.B: not conjugated) covalent bonds (even in the case of a long, in principle not conducting, alkyl chain) acts as an on/off switch on the ET process involving the ferrocene: the charge of the interface is driven by the external applied potential (bias), which can be switched on (charged, i.e.…”

“…Among the redox-active moieties, ferrocene-based derivatives form a class of attractive organic compounds, which can be considered as model systems. This is due to ferrocene structural stability, aromaticity, ease of modification, associated to a reversible single electron transfer process (Fc + /Fc), low oxidation/reduction potential, and easy to prepare self-assembled monolayers (SAMs) 20,21 . In view of the above fascinating behaviour, ferrocene based SAMs could be exploited as memory elements, where the ferrocene redox centre is used as the charge storage unit and considering the molecule in the neutral or oxidized form as the two states of a bit 22 .…”

“…In view of the above fascinating behaviour, ferrocene based SAMs could be exploited as memory elements, where the ferrocene redox centre is used as the charge storage unit and considering the molecule in the neutral or oxidized form as the two states of a bit 22 . This kind of supramolecular architectures were experimentally characterized in an extensive way as far as concerns the electron transfer ET process 19,21,23–27 , while from a theoretical point of view the fundamental knowledge of the ET dynamics, at an hybrid interface, is a subject yet open for discussion 20,28,29 . Indeed, most of the studies so far refer to ferrocene-terminated alkane thiols attached to a gold substrate.…”

Ferrocene Molecular Architectures Grafted on Si(111): A Theoretical Calculation of the Standard Oxidation Potentials and Electron Transfer Rate Constant

“…The striking result is that the connection of the ferrocene redox couple via a single (not conjugated) covalent bond acts as an on/off switch for the ET process. To the best of our knowledge, this is one of the few works in the literature reporting theoretically calculated values [ 22 , 40 , 41 , 71 ]. Remarkably, a semi-quantitative agreement between the experimental and theoretical values is found for the “short spacer” Si M –Me–FC system: our value is comparable to experimental results obtained for quite similar molecular interfacial architectures: Dalchiele and Roth reported and values, respectively [ 19 , 34 ].…”

“…In particular, chemi-adsorbed ferrocene moieties on silicon surfaces hold the promise to be exploited as a memory elements, where the ferrocene redox center is used as the charge storage component and the oxidation states (neutral or oxidized) as the two bits [ 16 ]. Similar molecular systems were experimentally characterized in a very extensive way, as far as the ET process is concerned [ 17 , 18 , 19 , 20 , 21 , 22 ]. However, from a theoretical point of view, the fundamental knowledge of the ET dynamics, at a hybrid interface, is a subject still open to discussion [ 23 , 24 ].…”