Dysprosium(III) and thulium(III) complexes of DO3A-monoanilides: An investigation of electronic effects on their relaxometric and amide-based PARACEST properties
Document Type
Article
Publication Date
1-1-2015
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).