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Title: Molecular Approach to Alkali-Metal Encapsulation by a Prussian Blue Analogue FeII/CoIII Cube in Aqueous Solution: A Kineticomechanistic Exchange Study
Author: Gonzálvez, Miguel A.
Bernhardt, Paul V.
Font Bardia, Ma. Mercedes
Gallen Ortiz, Albert
Jover Modrego, Jesús
Ferrer García, Montserrat
Martínez López, Manuel, 1957-
Keywords: Complexos metàl·lics
Metalls alcalins
Metal complexes
Alkali metals
Issue Date: 6-Dec-2021
Publisher: American Chemical Society
Abstract: The preparation of a series of alkali-metal inclusion complexes of the molecular cube [{CoIII(Me3-tacn)}4{FeII(CN)6}4]4- (Me3-tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane), a mixed-valent Prussian Blue analogue bearing bridging cyanido ligands, has been achieved by following a redox-triggered self-assembly process. The molecular cubes are extremely robust and soluble in aqueous media ranging from 5 M [H+] to 2 M [OH-]. All the complexes have been characterized by the standard mass spectometry, UV-vis, inductively coupled plasma, multinuclear NMR spectroscopy, and electrochemistry. Furthermore, X-ray diffraction analysis of the sodium and lithium salts has also been achieved, and the inclusion of moieties of the form {M-OH2}+ (M = Li, Na) is confirmed. These inclusion complexes in aqueous solution are rather inert to cation exchange and are characterized by a significant decrease in acidity of the confined water molecule due to hydrogen bonding inside the cubic cage. Exchange of the encapsulated cationic {M-OH2}+ or M+ units by other alkali metals has also been studied from a kineticomechanistic perspective at different concentrations, temperatures, ionic strengths, and pressures. In all cases, the thermal and pressure activation parameters obtained agree with a process that is dominated by differences in hydration of the cations entering and exiting the cage, although the size of the portal enabling the exchange also plays a determinant role, thus not allowing the large Cs+ cation to enter. All the exchange substitutions studied follow a thermodynamic sequence that relates with the size and polarizing capability of the different alkali cations; even so, the process can be reversed, allowing the entry of {Li-OH2}+ units upon adsorption of the cube on an anion exchange resin and subsequent washing with a Li+ solution.
Note: Versió postprint del document publicat a:
It is part of: Inorganic Chemistry, 2021, vol. 60, p. 18497-18422
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ISSN: 0020-1669
Appears in Collections:Articles publicats en revistes (Institut de Nanociència i Nanotecnologia (IN2UB))
Articles publicats en revistes (Institut de Química Teòrica i Computacional (IQTCUB))
Articles publicats en revistes (Química Inorgànica i Orgànica)

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