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A New Heptadentate Picolinate–Based Ligand and Its Corresponding Gd(III) Complex: the Effect of Picolinate versus Acetate Pendant on Complex Property

Abstract

To attain high relaxivity as well as stability, a new water–soluble, water–coordinated Gd(III) complex, which was synthesised by reacting equimolar amounts of picolinate–based ligand H4peada and GdCl3•xH2O at pH ~ 6.5, was examined. The number of inner sphere water molecules (q) in the complex was found to be 1.7 ± 0.1 from luminescence lifetime measurements of its Tb(III) congener, complex 2. At 1.41 T, 25 °C, and pH = 7.4, the longitudinal relaxivity (r1) value the complex was found to be 6.08 mM–1s–1; which remained almost constant in the pH range 4–10. The r1 relaxivity value has not been affected in the presence of 100 fold excess of bicarbonate and phosphate anions, whereas in case of fluoride ion, the value dropped to 4.6 mM–1s–1 due to a binding interaction of fluoride ion by replacing inner sphere water molecules of the complex. From potentiometric titration method, the stability constant of the complex was found to be logKGdL = 17.0 ± 0.08 (in 0.15 M KCl and 25 °C). At pH = 7.4, pGd value of ligand H4peada was found to be 14.01 which was comparable to the commercially available MRI contrast agent Omniscan®. Phantom MR images of the complex under clinical MR scanner at 1.5 T also demonstrated the usefulness of complex 1 as potential MRI contrast agent.

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Publication details

The article was received on 03 Nov 2017, accepted on 30 Nov 2017 and first published on 30 Nov 2017


Article type: Paper
DOI: 10.1039/C7DT04150K
Citation: Dalton Trans., 2017, Accepted Manuscript
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    A New Heptadentate Picolinate–Based Ligand and Its Corresponding Gd(III) Complex: the Effect of Picolinate versus Acetate Pendant on Complex Property

    C. Mukherjee, B. Phukan and R. Varshney, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT04150K

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