RT Journal Article
T1 Expanding the ligand classes used for Mn(II) complexation: oxa-aza macrocycles make the difference
A1 Kálmán, Ferenc K
A1 Nagy, Viktória
A1 Uzal Varela, Rocío
A1 Pérez Lourido, Paulo Antonio
A1 Esteban Gómez, David
A1 Garda, Zoltán
A1 Pota, Kristof
A1 Mezei, Roland
A1 Pallier, Agnès
A1 Tóth, Éva
A1 Platas Iglesias, Carlos
A1 Tircsó, Gyula
K1 2303 Química Inorgánica
AB We report two macrocyclic ligands based on a 1,7-diaza-12-crown-4 platform functionalized with acetate (tO2DO2A2−) or piperidineacetamide (tO2DO2AMPip) pendant arms and a detailed characterization of the corresponding Mn(II) complexes. The X−ray structure of [Mn(tO2DO2A)(H2O)]·2H2O shows that the metal ion is coordinated by six donor atoms of the macrocyclic ligand and one water molecule, to result in seven-coordination. The Cu(II) analogue presents a distorted octahedral coordination environment. The protonation constants of the ligands and the stability constants of the complexes formed with Mn(II) and other biologically relevant metal ions (Mg(II), Ca(II), Cu(II) and Zn(II)) were determined using potentiometric titrations (I = 0.15 M NaCl, T = 25 °C). The conditional stabilities of Mn(II) complexes at pH 7.4 are comparable to those reported for the cyclen-based tDO2A2− ligand. The dissociation of the Mn(II) chelates were investigated by evaluating the rate constants of metal exchange reactions with Cu(II) under acidic conditions (I = 0.15 M NaCl, T = 25 °C). Dissociation of the [Mn(tO2DO2A)(H2O)] complex occurs through both proton− and metal−assisted pathways, while the [Mn(tO2DO2AMPip)(H2O)] analogue dissociates through spontaneous and proton-assisted mechanisms. The Mn(II) complex of tO2DO2A2− is remarkably inert with respect to its dissociation, while the amide analogue is significantly more labile. The presence of a water molecule coordinated to Mn(II) imparts relatively high relaxivities to the complexes. The parameters determining this key property were investigated using 17O NMR (Nuclear Magnetic Resonance) transverse relaxation rates and 1H nuclear magnetic relaxation dispersion (NMRD) profiles.
PB Molecules
SN 14203049
YR 2021
FD 2021-03-10
LK http://hdl.handle.net/11093/2365
UL http://hdl.handle.net/11093/2365
LA eng
NO Molecules, 26(6): 1524 (2021)
NO Ministerio de Economía y Competitividad (España) | Ref. CTQ2016-76756-P
DS Investigo
RD 14-sep-2024