Heterometallic cobalt(ii) calix[6 and 8]arenes: synthesis, structure and electrochemical activity

Ignaszak, Anna; Patterson, Nigel; O'Brien, Connor; True, Allison; Elsegood, Mark R.J.; Prior, Timothy J.; Redshaw, Carl

Abstract

Heterometallic cobalt p-tert-butylcalix[6 and 8]arenes have been generated from the in situ reaction of lithium reagents (n-BuLi or t-BuOLi) or NaH with the parent calix[n]arene and subsequent reaction with CoBr2. The reverse route, involving the addition of in situ generated Li[Co(Ot-Bu)3] to p-tert-butylcalix[6 and 8]arene, has also been investigated. X-ray crystallography reveals the formation of complicated products incorporating differing numbers of cobalt and lithium or sodium centers, often with positional disorder, as well as, in some cases, the retention of halide. The electrochemical analysis revealed several oxidation events related to the subsequent oxidation of Co(ii) centers and the reduction of the metal cation at negative potentials. Moreover, the electrochemical activity of the phenol moieties of the parent calix[n]arenes resulted in dimerized products or quinone derivatives, leading to insoluble oligomeric products that deposit and passivate the electrode. Preliminary screening for electrochemical proton reduction revealed good activity for a number of these systems. Results suggest that [Co6Na(NCMe)6(μ-O)(p-tert-butylcalix[6]areneH)2Br]·7MeCN (6·7MeCN) is a promising molecular catalyst for electrochemical proton reduction, with a mass transport coefficient, catalytic charge transfer resistance and current magnitude at the catalytic turnover region that are comparable to those of the reference electrocatalyst (Co(ii)Cl2).

Citation

Ignaszak, A., Patterson, N., O'Brien, C., True, A., Elsegood, M. R., Prior, T. J., & Redshaw, C. (2022). Heterometallic cobalt(ii) calix[6 and 8]arenes: synthesis, structure and electrochemical activity. RSC advances, 12(19), 11672-11685. https://doi.org/10.1039/d2ra01009g

• Journal Article Type: Article
• Acceptance Date: Mar 14, 2022
• Online Publication Date: Apr 14, 2022
• Publication Date: Apr 14, 2022
• Deposit Date: Apr 15, 2022
• Publicly Available Date: Apr 19, 2022
• Journal: RSC Advances
• Print ISSN: 2046-2069
• Electronic ISSN: 2046-2069
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 12
• Issue: 19
• Pages: 11672-11685
• DOI: https://doi.org/10.1039/d2ra01009g
• Keywords: General Chemical Engineering; General Chemistry
• Public URL: https://hull-repository.worktribe.com/output/3970575