Polyelectrolyte‐Stabilized Nanotemplates Based on Gd(III) Complexes with Macrocyclic Tetra‐1,3‐diketones as a Positive MR Contrast Agents

The work presents for the first time aqueous colloids prepared from Gd(III) complexes with 1,3‐diketone derivatives as promising candidates for positive MR contrast agents (CA). The obtained colloids are based on reprecipitation of water insoluble Gd(III) complexes from organic to aqueous phases with further stabilization via layer‐by‐layer deposition of oppositely charged polyelectrolytes. A complex of experimental techniques reveals amorphous 3–6 nm sized Gd(III)‐based hard templates encapsulated into soft polyelectrolyte capsules. Magnetic field and coating effects on T 1 ‐ and T 2 ‐relaxivities for colloids with mono‐, bi‐ and tri‐layer polyelectrolyte deposition onto Gd(III)‐based templates are revealed. The relaxivities of the mono‐layered colloids are greater than those of commercial mononuclear Gd(III) CA. Water molecular correlation times in aqueous solutions of novel Gd(III)‐based nanoparticles were calculated. T 1 ‐ and T 2 ‐ weighted MRI data show strong positive contrast.