Dysprosium(III) and thulium(III) complexes of DO3A-monoanilides: an investigation of electronic effects on their relaxometric and amide-based PARACEST properties

Authors

Melissa M. Lewis, Department of Chemistry, The University of Western Ontario, London, ON N6A 5B7, Canada
Mark Milne, Department of Chemistry, The University of Western Ontario, London, ON N6A 5B7, Canada
Robert Bartha, Robarts Research Institute, Western University, 1151 Richmond St. N., London, ON N6A 5B7, Canada
Robert H.E. Hudson, Department of Chemistry, The University of Western Ontario, London, ON N6A 5B7, Canada

Document Type

Article

Publication Date

2-2015

Journal

Canadian Journal of Chemistry

Volume

93

Issue

2

First Page

244

Last Page

252

URL with Digital Object Identifier

10.1139/cjc-2014-0314

Abstract

A series of 1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate monoamide (DO3A-monoanilide) complexes Dy³⁺ and Tm³⁺ were prepared and their magnetic properties evaluated in the context of their potential use as pH sensors. The ligands varied by para-substitution of the aniline moiety and represent electron-withdrawing and electron-donating groups. Only the Tm³⁺ complexes produced chemical exchange saturation transfer (CEST) spectra with CEST intensities due to the amide proton ranging from 1% to 8%. A maximum CEST signal was observed under slightly alkaline conditions (pH ∼8) when electron-donating groups were present, whereas the strongly electron-withdrawing nitro group produced a maximum CEST at neutral pH (pH = 7). The T₁ and T₂ relaxivities of the Dy³⁺ and Tm³⁺ complexes were also assessed. The T₁ relaxivities of the Dy³⁺ and Tm³⁺ complexes were both low (r₁ ≤ 0.3 mM⁻¹ s⁻¹, 25 °C, pH = 7) but, as expected, the Dy³⁺ complexes had much higher T₂ relaxivities (r₂ = 2–7 mM⁻¹ s⁻¹, 25 °C, pH = 7) as compared to the Tm³⁺-based chelates (r₂ ≤ 0.09 mM⁻¹ s⁻¹, 25 °C, pH = 7).

Notes

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