Chiroptical Redox Switching of Tetra‐Cationic Derivatives of Azoniahelicenes

0505705 - ÚOCHB 2020 RIV DE eng J - Journal Article
Rončević, Igor - Jirásek, Michael - Severa, Lukáš - Reyes Gutierrez, Paul Eduardo - Teplý, Filip - Bednárová, Lucie - Hromadová, M. - Pospíšil, Lubomír
Chiroptical Redox Switching of Tetra‐Cationic Derivatives of Azoniahelicenes.
ChemElectroChem. Roč. 6, č. 12 (2019), s. 3002-3008. ISSN 2196-0216. E-ISSN 2196-0216
Institutional support: RVO:61388963
Keywords : helquats * redox switching * voltammetry * spectroelectrochemistry * circular dichroism
OECD category: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis)
Impact factor: 4.154, year: 2019
Method of publishing: Limited access
https://onlinelibrary.wiley.com/doi/abs/10.1002/celc.201900204

New tetra- and di-cationic azoniahelicenes provide electrochemical, spectroelectrochemical and electronic circular dichroism (ECD) data reflecting their differences in electron transfer (ET) kinetics. Di-cationic helquats containing two seven-membered rings are irreversibly reduced in two ET steps. Substitution by redox-active ethenylpyridinium in the alpha or gamma position with respect to nitrogen atoms of the helquat core yields tetra-cationic derivatives with reversible ET steps and communicating redox centres. Redox-inactive substituents in di-cationic azoniahelicenes retain ET irreversibility. Redox switching of ECD of tetra-cationic enantiomers was observed. Unlike fully aromatic helquat, the ECD response of tetra-cationic helquats to periodic reduction-oxidation cycles is slower, owing to a strong adsorption on electrodes. Quantum chemical calculations (DFT) indicate that the first ET step of tetra-cationic derivative substituted in the gamma position yields a folded structure, which favours the internal donor-acceptor interaction. This explains the spectroelectrochemical differences between both tetra-cations.
Permanent Link: http://hdl.handle.net/11104/0297121