Nickel(II) complex of a biradical

Structure, magnetic properties, high NMR temperature sensitivity and moderately fast molecular dynamics

Sergey P. Babailov, Eugenia V. Peresypkina, Yves Journaux, Kira E. Vostrikova

    Research output: Contribution to journalArticle

    5 Citations (Scopus)

    Abstract

    A novel nickel(II) complex of a tridentate iminonitroxyl biradical, [Ni(bisimpy)MeOH(ReO4)2], (1) (bisimpy = 2,6-bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-2-yl-1-oxyl)pyridine) was structurally and magnetically characterized. Due to an effective separation of the molecules in solid the magnetic behavior of 1 differs considerably from that of a related complex studied earlier, the spin carriers in the former having been strongly ferromagnetically coupled even at room temperature. Dynamic behavior of the paramagnetic cation [Ni(bisimpy)(CD3OD)3] in CD3OD solution was studied by 1H NMR. A temperature dependence of the spectrum of 1 has been analyzed using a dynamic NMR approach. It was shown that an interconversion of two conformers is liable for a fast dynamic process occurring in solution of 1 at elevated temperatures. An estimated value of ΔG(298 K) for this process was found to be of 59 ± 3 kJ/mol. It was confirmed that a considerable extension of the measurable rate constants range compared to that for diamagnetic compounds is a result of the paramagnetic chemical shifts in the Ni complex. Application of paramagnetic d-metal complexes as probes for studying of the free-energy changes in chemical exchange processes, as well as the advantages of this method compared to diamagnetic species are considered. The investigated complex represents an example of the new type of thermometric NMR sensors being to our knowledge is the most temperature sensitive reagent among the d-metal paramagnetic coordination compounds.

    Original languageEnglish
    Pages (from-to)405-412
    Number of pages8
    JournalSensors and Actuators, B: Chemical
    Volume239
    DOIs
    Publication statusPublished - 1 Feb 2017

    Fingerprint

    Nickel
    Molecular dynamics
    Magnetic properties
    Nuclear magnetic resonance
    nickel
    molecular dynamics
    magnetic properties
    nuclear magnetic resonance
    imidazoles
    metals
    Temperature
    temperature
    reagents
    chemical equilibrium
    Coordination Complexes
    pyridines
    Chemical shift
    Metal complexes
    free energy
    Pyridine

    Keywords

    • Biradical
    • Iminonitroxide
    • nickel(II)
    • Paramagnetic shift reagent
    • Temperature sensing

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Instrumentation
    • Condensed Matter Physics
    • Surfaces, Coatings and Films
    • Metals and Alloys
    • Electrical and Electronic Engineering
    • Materials Chemistry

    Cite this

    Nickel(II) complex of a biradical : Structure, magnetic properties, high NMR temperature sensitivity and moderately fast molecular dynamics. / Babailov, Sergey P.; Peresypkina, Eugenia V.; Journaux, Yves; Vostrikova, Kira E.

    In: Sensors and Actuators, B: Chemical, Vol. 239, 01.02.2017, p. 405-412.

    Research output: Contribution to journalArticle

    Babailov, Sergey P. ; Peresypkina, Eugenia V. ; Journaux, Yves ; Vostrikova, Kira E. / Nickel(II) complex of a biradical : Structure, magnetic properties, high NMR temperature sensitivity and moderately fast molecular dynamics. In: Sensors and Actuators, B: Chemical. 2017 ; Vol. 239. pp. 405-412.
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    AB - A novel nickel(II) complex of a tridentate iminonitroxyl biradical, [Ni(bisimpy)MeOH(ReO4)2], (1) (bisimpy = 2,6-bis(4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-2-yl-1-oxyl)pyridine) was structurally and magnetically characterized. Due to an effective separation of the molecules in solid the magnetic behavior of 1 differs considerably from that of a related complex studied earlier, the spin carriers in the former having been strongly ferromagnetically coupled even at room temperature. Dynamic behavior of the paramagnetic cation [Ni(bisimpy)(CD3OD)3] in CD3OD solution was studied by 1H NMR. A temperature dependence of the spectrum of 1 has been analyzed using a dynamic NMR approach. It was shown that an interconversion of two conformers is liable for a fast dynamic process occurring in solution of 1 at elevated temperatures. An estimated value of ΔG‡(298 K) for this process was found to be of 59 ± 3 kJ/mol. It was confirmed that a considerable extension of the measurable rate constants range compared to that for diamagnetic compounds is a result of the paramagnetic chemical shifts in the Ni complex. Application of paramagnetic d-metal complexes as probes for studying of the free-energy changes in chemical exchange processes, as well as the advantages of this method compared to diamagnetic species are considered. The investigated complex represents an example of the new type of thermometric NMR sensors being to our knowledge is the most temperature sensitive reagent among the d-metal paramagnetic coordination compounds.

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