Enzyme Control Over Ferric Iron Magnetostructural Properties

Abstract

Fe3+ complexes in aqueous solution can exist as discrete mononuclear species or multinuclear magnetically coupled species. Stimuli‐driven change to Fe3+ speciation represents a powerful mechanistic basis for magnetic resonance sensor technology, but ligand design strategies to exert precision control of aqueous Fe3+ magnetostructural properties are entirely underexplored. In pursuit of this objective, we rationally designed a ligand to strongly favor a dinuclear μ‐oxo‐bridged and antiferromagnetically coupled complex, but which undergoes carboxylesterase mediated transformation to a mononuclear high‐spin Fe3+ chelate resulting in substantial T1‐relaxivity increase. The data communicated demonstrate proof of concept for a novel and effective strategy to exert biochemical control over aqueous Fe3+ magnetic, structural, and relaxometric properties.

Macrocyclic complexes of Fe(iii) with mixed hydroxypropyl and phenolate or amide pendants as T1 MRI probes

“…2,3,5 The strong Lewis acidity of the Fe(III) center promotes deprotonation of bound waters at relatively low pK a values to form terminal hydroxides or bridging oxides. [15][16][17][18] Ready ionization of other ligand groups bound to Fe(III) can further complicate solution chemistry. 19,20 Further considerations as outlined in recent reviews involve controlling the oxidation and spin state of iron complexes under biological conditions.…”

Fluoropolymer-MOF Hybrids with Switchable Hydrophilicity for 19F MRI-Monitored Cancer Therapy

“…This aggregation induces rapid recognition by the mononuclear phagocytic system (MPS) leading to short circulation times, and unsatisfactory diagnosis and delivery efficiency . (2) Current ZIF-8-based MRI contrast agents mainly incorporate paramagnetic transition metal ions such as Mn 2+ , Fe 3+ , and Gd 3+ for 1 H MRI and hence suffer from a high endogenous background signal because 1 H is present in biological tissues in great abundance. − …”