Fluorinated Mn(III)/(II)‐Porphyrin with Redox‐Responsive 1H and 19F Relaxation Properties

A new fluorinated manganese porphyrin, (Mn‐TPP‐p‐CF3) is reported capable of providing, based on the Mn(III)/Mn(II) equilibrium, dual 1H relaxivity and 19F NMR response to redox changes. The physical‐chemical characterization of both redox states in DMSO‐d6/H2O evidenced that the 1H relaxometric and...

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Published inChemistry : a European journal Vol. 29; no. 53
Main Authors Pinto, Sara M A, Ferreira, Ana R R, Teixeira, Daniela S S, Nunes, Sandra C C, Ana L M Batista de Carvalho, Almeida, Joseany M S, Garda, Zoltan, Pallier, Agnés, Alberto A C C Pais, Brett, Christopher M A, Tóth, Éva, Marques, Maria P M, Pereira, Mariette M, Carlos F G C Geraldes
Format Journal Article
LanguageEnglish
Published Weinheim Wiley Subscription Services, Inc 21.09.2023
Subjects
Air monitoring
Ascorbic acid
Chelates
Chemistry
Deoxygenation
Fluorination
Magnetic resonance imaging
Manganese
NMR
Nuclear magnetic resonance
Porphyrins
Redox potential
Reduction
Reoxidation
Spectrometry
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Summary:A new fluorinated manganese porphyrin, (Mn‐TPP‐p‐CF3) is reported capable of providing, based on the Mn(III)/Mn(II) equilibrium, dual 1H relaxivity and 19F NMR response to redox changes. The physical‐chemical characterization of both redox states in DMSO‐d6/H2O evidenced that the 1H relaxometric and 19F NMR properties are appropriate for differential redox MRI detection. The Mn(III)‐F distance (dMn−F=9.7–10 Å), as assessed by DFT calculations, is well tailored to allow for adequate paramagnetic effect of Mn(III) on 19F T1 and T2 relaxation times. Mn‐TPP‐p‐CF3 has a reversible Mn(II)/Mn(III) redox potential of 0.574 V vs. NHE in deoxygenated aqueous HEPES/ THF solution. The reduction of Mn(III)‐TPP‐p‐CF3 in the presence of ascorbic acid is slowly, but fully reversed in the presence of air oxygen, as monitored by UV‐Vis spectrometry and 19F NMR. The broad 1H and 19F NMR signals of Mn(III)‐TPP‐p‐CF3 disappear in the presence of 1 equivalent ascorbate replaced by a shifted and broadened 19F NMR signal from Mn(II)‐TPP‐p‐CF3. Phantom 19F MR images in DMSO show a MRI signal intensity decrease upon reduction of Mn(III)‐TPP‐p‐CF3, retrieved upon complete reoxidation in air within ~24 h. 1H NMRD curves of the Mn(III)/(II)‐TPP‐p‐CF3 chelates in mixed DMSO/water solvent have the typical shape of Mn(II)/Mn(III) porphyrins.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.202301442