A seven-coordinate Mn(ii) complex with a pyridine-based 15-membered macrocyclic ligand containing one acetate pendant arm: structure, stability and relaxation properties
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61989592%3A15310%2F23%3A73622008" target="_blank" >RIV/61989592:15310/23:73622008 - isvavai.cz</a>
Result on the web
<a href="https://pubs.rsc.org/en/content/articlelanding/2023/dt/d3dt00701d" target="_blank" >https://pubs.rsc.org/en/content/articlelanding/2023/dt/d3dt00701d</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1039/d3dt00701d" target="_blank" >10.1039/d3dt00701d</a>
Alternative languages
Result language
angličtina
Original language name
A seven-coordinate Mn(ii) complex with a pyridine-based 15-membered macrocyclic ligand containing one acetate pendant arm: structure, stability and relaxation properties
Original language description
A new 15-membered pyridine-based macrocyclic ligand containing one acetate pendant arm (N-carboxymethyl-3,12,18-triaza-6,9-dioxabicyclo[12.3.1]octadeca-1(18),14,16-triene, L1) was synthesized and its Mn(II) complex MnL1 was investigated in the context of MRI contrast agent development. The X-ray molecular structure of MnL1 confirmed a coordination number of seven with an axially compressed pentagonal bipyramidal geometry and one coordination site available for an inner-sphere water molecule. The protonation constants of L1 and the stability constants of Mn(II), Zn(II), Cu(II) and Ca(II) complexes were determined by potentiometry, and revealed higher thermodynamic stabilities in comparison with complexes of 15-pyN(3)O(2), the parent macrocycle without an acetate pendant arm. The MnL1 complex is fully formed at physiological pH 7.4, but it shows fast dissociation kinetics, as followed by relaxometry in the presence of an excess of Zn(II). The short dissociation half-life estimated for physiological pH (ca. 3 minutes) is related to fast spontaneous dissociation of the non-protonated complex. At lower pH values, the proton-assisted dissociation pathway becomes important, while the Zn(II) concentration has no effect on the dissociation rate. O-17 NMR and H-1 NMRD data indicated the presence of one inner-sphere water molecule with a rather slow exchange (k(ex)(298) = 4.5 x 10(6) s(-1)) and provided information about other microscopic parameters governing relaxation. The relaxivity (r(1) = 2.45 mM(-1) s(-1) at 20 MHz, 25 degrees C) corresponds to typical values for monohydrated Mn(II) chelates. Overall, the acetate pendant arm in L1 has a beneficial effect with respect to 15-pyN(3)O(2) in increasing the thermodynamic stability and kinetic inertness of its Mn(II) complex, but leads to a reduced number of inner-sphere water molecules and thus lower relaxivity.
Czech name
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Czech description
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Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
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OECD FORD branch
10402 - Inorganic and nuclear chemistry
Result continuities
Project
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Continuities
S - Specificky vyzkum na vysokych skolach
Others
Publication year
2023
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Dalton Transactions
ISSN
1477-9226
e-ISSN
1477-9234
Volume of the periodical
52
Issue of the periodical within the volume
23
Country of publishing house
GB - UNITED KINGDOM
Number of pages
12
Pages from-to
7936-7947
UT code for WoS article
000993897800001
EID of the result in the Scopus database
2-s2.0-85160445439