Chalcogen controlled redox behaviour in peri-substituted S, Se and Te naphthalene derivatives
Abstract
Cyclic and square wave voltammetry of (PhE)2 peri-disubstituted naphthalene[1,8-cd]dichalcoganyls and acenaphthene[5,6-diyl]dichalcoganyls (E = S, Se, Te, 12 compounds) is reported. Mixed (E1 = Se, Te; E2 = Br, I) naphthalene[1,8-cd]halochalcoganyls were also investigated, as well as an exemplar bearing two PhS(=O) groups and another bearing one PhSe and one Ph2P(=S) substituent. The voltammetry, in CH2Cl2/0.4 M [nBu4N][PF6] at both platinum and glassy carbon macro-disk working electrodes, shows two sequential chemically reversible and electrochemically quasi-reversible oxidation processes, and the lack of accessible reductions. Additional oxidations above +1.5 V vs. Fc+/0 have not been investigated in detail. In situ and ex situ EPR spectroscopy conclusively demonstrate that both anodic processes are 1e transfers; persistent radical cations could be generated for all the dichalcoganyls except when E1 = E2 = Te; for the latter case thermally stable dications are generated instead. The complex possible solution conformations of these compounds in 0, +1 and +2 charge states were modelled with DFT at the B3LYP-D3(BJ)/6-31+G(d) level of theory in a CH2Cl2 PCM continuum solution model and adiabatic ionisation energies calculated, which correlate linearly (R = 0.88) with the Ea1p values. Crystal structures of four solvolysis and hydrolysis products of the ditellurium dications are reported and were modelled computationally. Interpretative comparisons to unsubstituted naphthalene[1,8-cd]dichalcogenoles are reported and the crystal structure of naphtho(1,8-cd)(1,2-dithiolium) tetrafluoroborate has been obtained. This is the first structure reported for any salt of this cation radical. Electron transfer mechanisms of both the (PhE)2 and E2 peri-disubstituted naphthalene series are correlated using a redox molecular orbital interpretative framework.
Citation
Roemmele , T L , Knight , F R , Crawford , E , Robertson , S D , Bode , B E , Buehl , M , Slawin , A M Z , Woollins , J D & Boeré , R T 2023 , ' Chalcogen controlled redox behaviour in peri -substituted S, Se and Te naphthalene derivatives ' , New Journal of Chemistry , no. 46 , 22363 . https://doi.org/10.1039/D2NJ04737C
Publication
New Journal of Chemistry
Status
Peer reviewed
ISSN
1144-0546Type
Journal article
Description
Funding: Research funding for this work was provided by ongoing Discovery Grants from the Natural Sciences and Engineering Research Council of Canada (Lethbridge). A Sabbatical leave from the University of Lethbridge (RTB), and an RSE Fellows Visitors to Scotland grant from the Royal Society of Edinburgh (JDW, RTB) are gratefully acknowledged.Collections
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