Dinuclear Fe(III) Hydroxypropyl-Appended Macrocyclic Complexes as MRI Probes
Year: 2021
Type: article
Abstract: Four high-spin Fe(III) macrocyclic complexes, including three dinuclear and one mononuclear complex, were prepared toward the development of more effective iron-based magnetic resonance imaging (MRI) contrast agents. All four complexes contain a 1,4,7-triazacyclononane macrocyclic backbone with two hydroxypropyl pendant groups, an ancillary aryl or biphenyl group, and a coordination site for a water ligand. The pH potentiometric titrations support one or two deprotonations of the complexes, most likely deprotonation of hydroxypropyl groups at near-neutral pH. Variable-temperature 17 O NMR studies suggest that the inner-sphere water ligand is slow to exchange with bulk water on the NMR time scale. Water proton T 1 relaxation times measured for solutions of the Fe(III) complexes at pH 7.2 showed that the dinuclear complexes have a 2- to 3-fold increase in r 1 relaxivity in comparison to the mononuclear complex per molecule at field strengths ranging from 1.4 T to 9.4 T. The most effective agent, a dinuclear complex with macrocycles linked through para-substitution of an aryl group (Fe 2 (PARA)), has an r 1 of 6.7 mM –1 s –1 at 37 °C and 4.7 T or 3.3 mM –1 s –1 per iron center in the presence of serum albumin and shows enhanced blood pool and kidney contrast in mice MRI studies.
Source: Inorganic Chemistry
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3166981230