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Enhanced selectivity for Mg2+ with a phosphinate-based chelate: APDAP versus APTRA

Walter, Edward R.H.; Fox, Mark A.; Parker, David; Williams, J.A. Gareth

Enhanced selectivity for Mg2+ with a phosphinate-based chelate: APDAP versus APTRA Thumbnail


Authors

Edward R.H. Walter



Abstract

o-Aminophenol-N,N,O-triacetate, known as APTRA, is one of the most well-established ligands for targeting magnesium ions but, like other aminocarboxylate ligands, it binds Ca2+ much more strongly than Mg2+. The synthesis of an O-phosphinate analogue of APTRA is reported here, namely o-aminophenol-N,N-diacetate-O-methylene-methylphosphinate, referred to as APDAP. Metal binding studies monitored using UV-visible spectroscopy show that the affinity of APDAP for Ca2+ is reduced by over two orders of magnitude compared to APTRA, and for Zn2+ by over three orders of magnitude, whereas the affinity for Mg2+ is attenuated to a much lesser extent, by a factor of only about 7. The selectivity towards Mg2+ is thus substantially improved. DFT calculations support the notion that longer P–O and P–C bonds in APDAP (compared to corresponding C–O and C–C bonds in APTRA) favour a larger angle at the metal, an effect that is less unfavourable for smaller ions like Mg2+ than for larger ions such as Ca2+. Derivatives of APDAP can be anticipated that will offer improved sensing of Mg2+ in the presence of Ca2+, in the physiologically important millimolar concentration range.

Citation

Walter, E. R., Fox, M. A., Parker, D., & Williams, J. G. (2018). Enhanced selectivity for Mg2+ with a phosphinate-based chelate: APDAP versus APTRA. Dalton Transactions, 47(6), 1755-1763. https://doi.org/10.1039/c7dt04698g

Journal Article Type Article
Acceptance Date Jan 5, 2018
Online Publication Date Jan 16, 2018
Publication Date Feb 14, 2018
Deposit Date Jan 17, 2018
Publicly Available Date Jan 5, 2019
Journal Dalton Transactions
Print ISSN 1477-9226
Electronic ISSN 1477-9234
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 47
Issue 6
Pages 1755-1763
DOI https://doi.org/10.1039/c7dt04698g