Both isotopes of silver [107Ag and 109Ag] were simultaneously polarized by dynamic nuclear polarization (DNP) Large liquid-state NMR enhancements were achieved allowing the Ag NMR characterization of the complexes in mM concentration range. Since both isotopes have long T1, the hyperpolarized NMR signal of one isotope could still be observed even after the magnetization of the other isotope had already been destroyed by rf excitation pulses.

Both isotopes of silver [ 107 Ag and 109 Ag] were simultaneously polarized by dynamic nuclear polarization (DNP) Large liquid-state NMR enhancements were achieved allowing the Ag NMR characterization of the complexes in mM concentration range. Since both isotopes have long T 1 , the hyperpolarized NMR signal of one isotope could still be observed even after the magnetization of the other isotope had already been destroyed by rf excitation pulses. KeywordsAg; NMR; ligands; isotopes; dynamic nuclear polarization Silver compounds and complexes are important class of materials due to the extensive inorganic, organometallic, and medicinal chemistry of the Ag + ion. A number of Ag + complexes, in particular, the diphosphine complexes Ag(dppe) 2 + and Ag(dppp) 2 + , have been shown to have potent antimicrobial and anticancer properties. [1] Complexes of the β-emitting radionuclide 111 Ag such as Ag(dotete) + have been suggested for the targeted radiotherapy of cancer. [2] Ag has two naturally abundant, spin I=1/2 isotopes: 107 Ag (51.83 %, 107 γ=1.723 MHz/T) and 109 Ag (48.17 %, 109 γ=1.9808 MHz/T) and thus, NMR spectroscopy would be a very useful method for the structural characterization of silver complexes as well as for the study of reactions involving Ag + ions. [3] However, Ag NMR is hampered by two major difficulties which arise from the very low gyromagnetic ratio γ of Ag isotopes: (i) low sensitivity and (ii) long spin-lattice relaxation time T 1 . [3] In spite of the major advances in NMR technology, conventional Ag NMR still requires high concentrations and/or prohibitively long experimental acquisition times. For instance, INEPT experiments can only improve the Ag NMR signal enhancement by a factor of 8.7.

In this work, we describe a novel DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) based ligand with a chromophoric tropone coordinating sidearm (1). Ln3+ complexes of 1 have one inner sphere water molecule. The r1 relaxivity of Gd1 is similar to that of the commercial Gd-based MRI agents. The neutral O-donor atom of the tropone moiety slows down the water exchange rate by a factor of 3 compared to GdDOTA. In addition, Nd1 and Yb1 complexes exhibit significant NIR emission in aqueous solutions indicating that the tropone unit is an efficient sensitizer for these Ln3+-ions. Therefore, this new ligand is a promising platform for the design of Ln3+ based dual MR/optical imaging probes.