Long-Range Intramolecular Electronic Communication in Bis(ferrocenylethynyl) Complexes Incorporating Conjugated Heterocyclic Spacers: Synthesis, Crystallography, and Electrochemistry

Abstract

A new series of bis(ferrocenylethynyl) complexes, 3-7, and a mono(ferrocenylethynyl) complex, 8, have been synthesized incorporating conjugated heterocyclic spacer groups, with the ethynyl group facilitating an effective long-range intramolecular interaction. The complexes were characterized by NMR, IR, and UV-vis spectroscopy as well as X-ray crystallography. The redox properties of these complexes were investigated using cyclic voltammetry and spectroelectrochemistry. Although there is a large separation of ∼14 Å between the two redox centers, ΔE(1/2) values in this series of complexes ranged from 50 to 110 mV. The appearance of intervalance charge-transfer bands in the UV-vis-near-IR region for the monocationic complexes further confirmed effective intramolecular electronic communication. Computational studies are presented that show the degree of delocalization across the Fc-C≡C-C≡C-Fc (Fc = C5H5FeC5H4) highest occupied molecular orbital.

Multiferrocenyl Cobalt‐Based Sandwich Compounds

“…Predominantly, Δ E °′ correlates nicely with the electronic coupling parameter , , . However, a high degree of electronic coupling was observed for species with a low redox splitting , . Furthermore, there are class I compounds according to the classification of Robin and Day known, that show high Δ E °′ values , , , …”

Ferrocenylethynyl - a versatile platform for new molecules to novel materials

“…Shah et al recently reported a new series of bis(ferrocenylethynyl) complexes incorporating novel heterocyclic spacers [1]. They also synthesized one mono(ferrocenylethynyl) compound for comparison with the bis(ferrocenylethynyl)s (see Chart 9).…”

“…ven six decades after its discovery, ferrocene still remains a hot topic for new materials researchers. Ferrocene and ferrocene-based materials are versatile and have been successfully used in a variety of domains such as electrochemistry [1][2][3][4], sensors [5], nonlinear optics and luminescent systems [6,7], pharmaceuticals [8,9], automobiles [10,11], fine organic synthesis [12], materials chemistry [13][14][15][16][17], liquid crystals [18][19][20], paramagnetic and ferromagnetic systems [21,22] and bio-organometallic chemistry [23], etc. During its long journey ferrocene chemistry has witnessed the emergence of many structural motifs built around the ferrocene platform, suitably grafting ene, phenylene(ethylene) and ethynyl spacers between two ferrocenes or between a ferrocene and an organic/inorganic group.…”

“…(i) data for the neutral spectra, (ii) the mono-cation, and difference spectra (iii-v) are shown. Adapted with permission from ref[1]. Copyright (2013) American Chemical Society.…”

Synthesis and Characterisation of Fused Heterocyclic Molecular Rods: A Combined Experimental and Theoretical Study on Diethynyl Dithienothiophenyl Derivatives

“…To date, there are only a few reports on DTT alkyne derivatives,‐ that present a thorough characterisation of a range of structurally diverse units. These include metallated alkynes such as gold, iron, platinum and ferrocene, while DFT modeling, was reported for structures yet to be prepared in the literature, for applications such as molecular wires.…”