Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

EPR/ENDOR and computational study of outer sphere interactions in copper complexes of phenolic oximes

Healy, M. R., Carter, Emma, Fallis, Ian, Forgan, R. S., Gordan, R. J., Kamenetzky, E, Love, J. B., Morrison, C. A., Murphy, Damien and Tasker, P. A. 2015. EPR/ENDOR and computational study of outer sphere interactions in copper complexes of phenolic oximes. Inorganic Chemistry 54 (17) , pp. 8465-8473. 10.1021/acs.inorgchem.5b01180

Full text not available from this repository.

Abstract

Copper complexes of the phenolic oxime family of ligands (3-X-salicylaldoximes) are used extensively as metal solvent extractants. Incorporation of electronegative substituents in the 3-position, ortho to the phenol group, can be used to buttress the interligand H-bonding, leading to an enhancement in extractant strength. However, investigation of the relevant H-bonding in these complexes can be exceedingly difficult. Here, we have combined EPR, ENDOR, DFT, and X-ray crystallography to study this effect. Analysis of the 1H ENDOR data revealed a variation in the Cu···H16 (oxime proton) distance from 2.92 Å for the unsubstituted complex [Cu(L2)2] to 3.65 Å for the X = CH2N(C6H13)2 substituted complex [Cu(L3)2]. DFT calculations showed that this variation is caused by changes to the length and strength of the H-bond between the oximic hydrogen and the phenolate oxygen. Noticeable changes to the Cu···H15 (azomethine proton) distances and the Cu···N bonding parameters were also observed in the two complexes, as revealed through the NA and NQ ENDOR data. Distortions in the structure of the complex and variations in the oximic proton to phenolate oxygen H-bond strength caused by the substituent (X) were confirmed by DFT and X-ray crystallography. DFT directly evidenced the importance of the interaction between H16 and the amine nitrogen of CH2N(C6H13)2 in the buttressed complex and indicated that the high strength of this interaction may not necessarily lead to an enhancement of copper extraction, as it can impose an unfavorable geometry in the inner coordination sphere of the complex. Therefore, ENDOR, DFT, and X-ray structural data all indicate that the aminomethyl substituent (X) ortho to the phenolic oxygen atom provides a particularly strong buttressing of interligand H-bonding in these copper complexes and that these outer sphere interactions can significantly influence structure and stability.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: American Chemical Society
ISSN: 0020-1669
Last Modified: 24 Jun 2018 22:27
URI: http://orca.cf.ac.uk/id/eprint/86863

Citation Data

Cited 2 times in Google Scholar. View in Google Scholar

Cited 6 times in Scopus. View in Scopus. Powered By Scopus® Data

Cited 1 time in Web of Science. View in Web of Science.

Actions (repository staff only)

Edit Item Edit Item