Unexpected changes in the population of coordination isomers for the lanthanide ion complexes of DOTMA-tetraglycinate

Cemile Kumas, W. Shirangi Fernando, Piyu Zhao, Martín Regueiro-Figueroa, Garry E. Kiefer, André F. Martins, Carlos Platas-Iglesias, A. Dean Sherry

Research output: Contribution to journalArticle

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Abstract

Lanthanide complexes with DOTA-tetraglycinate (DOTA-(gly)4) heavily favor the square antiprismatic (SAP) coordination isomer in aqueous solution, a structural feature that has made them useful as water-based paraCEST agents. In an effort to create amide-based paraCEST agents with rapid water exchange rates, we prepared the analogous tetraglycinate complexes with DOTMA, a ligand known to favor the twisted square antiprismatic (TSAP) coordination structures. Unexpectedly, NMR investigations show that the LnDOTMA-(gly)4 complexes, like the LnDOTA-(gly)4 complexes, also favor the SAP isomers in solution. This observation led to density functional theory (DFT) calculations in order to identify the energy terms that favor the SAP structures in lanthanide complexes formed with macrocyclic DOTA- and DOTMA-tetraamide ligands. The DFT calculations revealed that, regardless the nature of the ligand, the TSAP isomers present more negative hydration energies than the SAP counterparts. The extent to which the TSAP isomer is stabilized varies, however, depending on the ligand structure, resulting in different isomeric populations in solution.

Original languageEnglish (US)
Pages (from-to)9297-9305
Number of pages9
JournalInorganic Chemistry
Volume55
Issue number18
DOIs
StatePublished - Sep 19 2016

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glycyl-glycyl-glycyl-glycine
Lanthanoid Series Elements
Isomers
isomers
Ions
Ligands
ligands
Density functional theory
ions
density functional theory
Water
Amides
Hydration
water
amides
hydration
Nuclear magnetic resonance
aqueous solutions
nuclear magnetic resonance
N-(1-(2,3-dioleyloxy)propyl)-N,N,N-trimethylammonium

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Unexpected changes in the population of coordination isomers for the lanthanide ion complexes of DOTMA-tetraglycinate. / Kumas, Cemile; Fernando, W. Shirangi; Zhao, Piyu; Regueiro-Figueroa, Martín; Kiefer, Garry E.; Martins, André F.; Platas-Iglesias, Carlos; Sherry, A. Dean.

In: Inorganic Chemistry, Vol. 55, No. 18, 19.09.2016, p. 9297-9305.

Research output: Contribution to journalArticle

Kumas, C, Fernando, WS, Zhao, P, Regueiro-Figueroa, M, Kiefer, GE, Martins, AF, Platas-Iglesias, C & Sherry, AD 2016, 'Unexpected changes in the population of coordination isomers for the lanthanide ion complexes of DOTMA-tetraglycinate', Inorganic Chemistry, vol. 55, no. 18, pp. 9297-9305. https://doi.org/10.1021/acs.inorgchem.6b01390
Kumas, Cemile ; Fernando, W. Shirangi ; Zhao, Piyu ; Regueiro-Figueroa, Martín ; Kiefer, Garry E. ; Martins, André F. ; Platas-Iglesias, Carlos ; Sherry, A. Dean. / Unexpected changes in the population of coordination isomers for the lanthanide ion complexes of DOTMA-tetraglycinate. In: Inorganic Chemistry. 2016 ; Vol. 55, No. 18. pp. 9297-9305.
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