Monitoring the substrate-induced spin-state distribution in a Cobalt(II)-Salen complex by EPR and DFT

Magri, Giuseppina, Folli, Andrea ORCID: https://orcid.org/0000-0001-8913-6606 and Murphy, Damien M. ORCID: https://orcid.org/0000-0002-5941-4879 2022. Monitoring the substrate-induced spin-state distribution in a Cobalt(II)-Salen complex by EPR and DFT. European Journal of Inorganic Chemistry 2022 (9) , e202101071. 10.1002/ejic.202101071

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Abstract

Ground state changes of (R,R’)-N,N’-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamino Co(II), following coordination of various pyridyl substrate has been examined by CW EPR, pulsed relaxation measurements and DFT. The solution-based Co(II) complex possesses a low spin (LS) state urn:x-wiley:14341948:media:ejic202101071:ejic202101071-math-0001 (with g-values of 1.96, 1.895, 3.14). Upon coordination of the pyridyl substrate, the resulting bound adduct reveals a distribution of LS ‘base-on’ species, possessing a urn:x-wiley:14341948:media:ejic202101071:ejic202101071-math-0002 electronic ground state (with g-values of 2.008, 2.2145, 2.46) and a high spin (HS) species (with geff = 4.6). DFT indicated that the energy gap between the LS and HS state is dramatically lowered (ΔE < 25 kJmol−1) following substrate coordination. DFT suggests the main geometrical difference between the LS and HS systems is the severe puckering of the N2O2 ligand backbone. The results revealed a tentative dependency on the pKa−H of the substrates for the spin distribution where, in most cases, the higher pKa−H substrate values favoured the HS species.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Additional Information:	This is an open access article under the terms of the Creative Commons Attribution License
Publisher:	Wiley-VCH Verlag
ISSN:	1434-1948
Funders:	EPSRC
Date of First Compliant Deposit:	9 March 2022
Date of Acceptance:	11 February 2022
Last Modified:	06 Jan 2024 04:24
URI:	https://orca.cardiff.ac.uk/id/eprint/148200

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