Development and Characterisation of Highly Conjugated Functionalised Ferrocenylene Macrocycles

Abstract

Multiple synthetic pathways were explored for the preparation of ethynylarene-containing ferrocenylene macrocyles. Accordingly, the synthesis of novel bis-and tris-ferrocenylene macrocycles, containing a diethynylpyridine bridging group was achieved, and evidence is also provided for a number of linearanalogues formed as by-products. The electrochemical properties of the macrocycles were examined, and it was shown that the number of observable redox processes does not necessarily correlate with the number of redox active centres. Additionally, examination of the comproportionation constants of the trisferrocenylene macrocycle demonstrated that the monocationic and dicationic species could be assigned to class II and I/II borderline of the Robin-Day classification, respectively. The synthesis of these molecules presents an opportunity towards the development of conjugated ferrocenylene macrocycles for electronic applications.

A convenient synthesis of ferrocene-(ethynylphenyl)thioacetates

“…All compounds displayed a single one-electron redox process, associated with an Fe 2+ /Fe 3+ pair on the central ferrocene unit, except for compounds 6a / 6 , which showed two distinct one-electron processes (arising from separate Fe 2+ /Fe 3+ pairs on the two ferrocenyl centres). 15 All these processes were determined to be both chemically reversible, with i pa / i pc ≈ 1, and electrochemically reversible, with Δ E ≈ 59 mV. Scan-rate dependence experiments were also performed, by collecting voltammograms at several different scan-rates, demonstrating that all of these processes are also diffusion controlled, with i p ∝ (scan-rate) 1/2 , with the exception of 8a , which displayed a clear change in its redox profile over successive scans, possibly suggesting either molecular instability, or alternatively, deposition of the molecule onto the electrode when these specific measurement conditions were applied (see ESI section 2†).…”

Side-Chain Type Ferrocene Macrocycles

“…To date, the main-chain macrocycles incorporating ferrocene units usually feature 1,1′-disubstituted ferrocene units , and conjugated linkages, such as pyrene , or 1,3-diethynylbenzene − (Figure c). The inherent rotation of the cyclopentadienyl (Cp) ring in ferrocene likely contributes to the formation of these twisted systems by reducing the strain.…”

A convergent growth approach to electroactive ferrocene rich carbosilane- and siloxane-based dendrons, dendrimers, and dendronized polymers

“…For instance, the incorporation of electroactive organometallic units into dendrimer structures is an especially attractive target area because such highly branched macromolecules are good multielectron-transfer mediators in electrocatalytic processes of biological and industrial importance, and this remains a topical challenge. In particular, covalent incorporation of ferrocene units into dendrimers, 9 polymers, 10 and macrocycles 11 can greatly modify their physical and chemical properties. Ferrocene is an ideal donor moiety and the ease of functionalization, the chemical stability, and the diamagnetism in the neutral state (allowing NMR characterization) make this metallocene one of the mostly used building blocks to construct metallomacromolecular architectures.…”