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We investigated the coordination properties of original macrocyclic Ln3+ complexes comprising an imidazothiadiazole heterocycle. The thermodynamic stability of the Gd3+ complex was determined by a combination of potentiometric and photophysical measurements. The kinetic inertness was assessed in highly acidic media. The solution structure of the Ln3+ complex was unambiguously determined by a set of photophysical measurements and ¹H, 13C, 89Y NMR data in combination with DFT calculations, which proved coordination of the heterocycle to Ln3+. The ability of the imidazothiadiazole moiety to sensitize Tb3+ luminescence was investigated. Finally, the relaxation properties were investigated by recording ¹H nuclear magnetic relaxation dispersion (NMRD) profiles and 17O measurements. The water exchange rate is similar to that of GdDOTA as the less negative charge of the ligand is compensated for by the presence of a bulky heterocycle. Relaxivity is constant over a large range of pH values, demonstrating the favorable properties of the complex for imaging purposes. [ABSTRACT FROM AUTHOR]

We present the in vitro characterisation of a Gd3+-based contrast agent that responds to Zn2+ upon interaction with Human Serum Albumin. We show that the contradictory in vivo behaviour is related to Gd3+-accumulation in Zn-rich tissues. This highlights the importance of the biodistribution of such contrast agents. [ABSTRACT FROM AUTHOR]

We propose quantitative assessment of zinc by combining nuclear and MR imaging. We use a cocktail of a Gd3+-complex providing a Zn2+-dependent MRI response and its 165Er3+ analogue allowing for concentration assessment. 165Er is readily obtained in a cyclotron and purified, which is indispensable for successful quantification of metal ions. [ABSTRACT FROM AUTHOR]

We investigated the coordination properties of original macrocyclic Ln 3+ complexes comprising an imidazothiadiazole heterocycle. The thermodynamic stability of the Gd 3+ complex was determined by a combination of potentiometric and photophysical measurements. The kinetic inertness was assessed in highly acidic media. The solution structure of the Ln 3+ complex was unambiguously determined by a set of photophysical measurements and 1 H, 13 C, 89 Y NMR data in combination with DFT calculations, which proved coordination of the heterocycle to Ln 3+ . The ability of the imidazothiadiazole moiety to sensitize Tb 3+ luminescence was investigated. Finally, the relaxation properties were investigated by recording 1 H nuclear magnetic relaxation dispersion (NMRD) profiles and 17 O measurements. The water exchange rate is similar to that of GdDOTA as the less negative charge of the ligand is compensated for by the presence of a bulky heterocycle. Relaxivity is constant over a large range of pH values, demonstrating the favorable properties of the complex for imaging purposes.

We propose quantitative assessment of zinc by combining nuclear and MR imaging. We use a cocktail of a Gd3+-complex providing a Zn2+-dependent MRI response and its 165Er3+ analogue allowing for concentration assessment. 165Er is readily obtained in a cyclotron and purified, which is indispensable for successful quantification of metal ions.