A magnetic resonance imaging contrast agent capable of detecting hydrogen peroxide

Abstract

The redox-active ligand N-(2-hydroxy-5-methylbenzyl)-N,N′,N′- tris(2-pyridinylmethyl)-1,2-ethanediamine (Hptp1) was prepared and complexed to manganese(II). The isolated [Mn(Hptp1)(MeCN)]2+ serves as a magnetic resonance imaging contrast agent, with an r1 value comparable to those of other mononuclear gadolinium(III) and manganese(II) complexes. The metal and ligand are stable in aerated aqueous solutions, but the addition of H2O2 causes the complex to oxidatively couple to itself through a bimolecular reaction involving the phenol groups of two Hptp1 ligands. The binuclear product is less paramagnetic per manganese(II) than its mononuclear precursor, lowering the measured r1 per manganese(II). The manganese(II) complex with Hptp1 can thereby serve as a sensor for oxidative stress. © 2012 American Chemical Society.