ic6b02964_si_002.cif (73.69 kB)
Adding a Second Quinol to a Redox-Responsive MRI Contrast Agent Improves Its Relaxivity Response to H2O2
dataset
posted on 2017-02-13, 15:49 authored by Meng Yu, Meghan B. Ward, Alicja Franke, Stephen L. Ambrose, Zachary L. Whaley, Thomas Miller Bradford, John D. Gorden, Ronald J. Beyers, Russell C. Cattley, Ivana Ivanović-Burmazović, Dean D. Schwartz, Christian R. GoldsmithThe overproduction
of reactive oxygen species has been linked to a wide array of health
disorders. The ability to noninvasively monitor oxidative stress in vivo could provide substantial insight into the progression
of these conditions and, in turn, could facilitate the development
of better diagnosis and treatment options. A mononuclear Mn(II) complex
with the redox-active ligand N,N′-bis(2,5-dihydroxybenzyl)-N,N′-bis(2-pyridinylmethyl)-1,2-ethanediamine (H4qtp2)
was made and characterized. A previously prepared Mn(II) complex with
a ligand containing a single quinol subunit was found to display a
modest T1-derived relaxivity response
to H2O2. The introduction of a second redox-active
quinol both substantially improves the relaxivity response of the
complex to H2O2 and reduces the cytotoxicity
of the sensor but renders the complex more susceptible to transmetalation.
The addition of H2O2 partially oxidizes the
quinol subunits to para-quinones, concomitantly increasing
the r1 from 5.46 mM–1 s–1 to 7.17 mM–1 s–1. The oxidation of the ligand enables more water molecules to coordinate
to the metal ion, providing an explanation for the enhanced relaxivity.
That the diquinol complex is only partially oxidized by H2O2 is attributed to its activity as an antioxidant; the
complex can both catalytically degrade superoxide and serve as a hydrogen
atom donor.