Bistability of Fc-PTM-Based Dyads: The Role of the Donor Strength

Abstract

Bistability of valence tautomeric donor–acceptor dyads formed by covalently linking a ferrocene-based electron-donor and the perchlorotriphenylmethyl radical, as the electron-acceptor, is tuned via a chemical modification of the ferrocene group. Specifically, the methylation of the ferrocene unit increases the strength of the donor group stabilizing the zwitterionic state in polar solvents and leading to an intriguing coexistence of neutral and zwitterionic species in solvents of intermediate polarity. Bistability in the crystalline phase is demonstrated by temperature dependent Mössbauer spectra. This complex and interesting behavior is quantitatively rationalized in the framework of a bottom-up modeling strategy. Optical spectra in solution are first analyzed to extract and parametrize an effective two-state molecular model, which is then adopted to rationalize the observed bistability in the solid state as due to cooperative electrostatic interchromophore interactions.

Reversible switching of the Au(111) work function by near infrared irradiation with a bistable SAM based on a radical donor–acceptor dyad

“…1). [23][24][25][26][27][28] The acceptor strengths of these two units are different because of their distinct electronic configurations, i.e., an open-shell for the radical and a closed-shell for the non-radical form. In both SAMs, one cyclopentadienyl ring of Fc is connected to the acceptor unit by a vinylene bridge while the other ring is connected by a carboxylate alkyl chain to a disulfide group (DS) acting as anchoring group for binding to Au(111) substrate (see Fig.…”

Design of Perchlorotriphenylmethyl (PTM) Radical‐Based Compounds for Optoelectronic Applications: The Role of Orbital Delocalization

“…Several works have demonstrated the possibility of tuning the PTM optical properties by introducing electroactive groups connected to PTM by vinylene bridges (see Figure ). In particular, recent works,, have studied the influence of the introduction of donor groups (D) connected to the PTM, which acts as an electron acceptor (A); as a consequence of the strong D‐A character, Intramolecular Electron Transfer (IET) absorption bands appear in the near IR region. However, these IET absorption bands have a very low intensity so that the absorption spectra remain dominated by the intense absorption band associated to the PTM radical (unless in the case of star trisubstituted compound where additional bands at low energy also appear) ,.…”

Effect of the Molecular Polarizability of SAMs on the Work Function Modification of Gold: Closed‐ versus Open‐Shell Donor–Acceptor SAMs

“…Another compound with interesting physical properties is a donor‐acceptor (D–A) dyad based on ferrocene (Fc) as donor unit and polychlorotriphenylmethyl (PTM) radical as an acceptor unit, connected by a conjugated vinylene bridge . This D–A radical dyad exhibits high chemical and thermal stability and presents very different electronic, optical, and magnetic properties compared to the corresponding closed‐shell form where the PTM radical unit is replaced by a non‐radical polychlorotriphenylmethane (αHPTM) one .…”