Solvent-, Cation- and Anion-Induced Structure Variations in Manganese-Based TCNQF4 Complexes: Synthesis, Crystal Structures, Electrochemistry and Their Catalytic Properties

Jinzhen Lu, Brendan F. Abrahams, Robert W. Elliott, Richard Robson, Alan M. Bond, Lisandra L. Martin

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2 Citations (Scopus)

Abstract

The reaction of Mn(BF4)2⋅x H2O with (Pr4N)2TCNQF4 (TCNQF4=2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) in a mixture of CH3OH/CH2Cl2 gives a 2:3 stoichiometric complex of (Pr4N)2[Mn2(TCNQF4)3(CH3OH)2] (1). If the solvent system used for the crystallisation of 1 is changed to CH3OH/DMF, then a different product, [Mn(TCNQF4)(DMF)2]⋅(CH3OH)2 (2), is obtained. The use of Li2TCNQF4 instead of (Pr4N)2TCNQF4 leads to the generation of [Mn2(TCNQF4)2(DMF)4]⋅3 DMF (3). An unexpected mixed oxidation state network with a composition of [MnII 4MnIII 16O10(OH)6(OCH3)24(TCNQF4)2](NO3)2⋅24 CH3OH (4), is formed if Mn(NO3)2⋅x H2O is used in place of Mn(BF4)2⋅x H2O in the reaction that leads to the formation of 3. Compounds 1–3 have been characterised by X-ray crystallography; FTIR, Raman and UV/Vis spectroscopy; and electrochemistry. Compound 4 has only been analysed by X-ray crystallography and vibrational spectroscopy (Raman, FTIR), owing to rapid deterioration of the compound upon exposure to air. These results indicate that relatively minor changes in reaction conditions have the potential to yield products with vastly different structures. Compound 1 adopts an anionic 2D network with unusual π-stacked dimers of the TCNQF4 2− dianion, whereas 2 and 3 are composed of similar neutral sheets of [Mn(TCNQF4)(DMF)2]. Interestingly, the solvent has a significant influence on the stacking of the sheets in the structures of 2 and 3. In compound 4, clusters with a composition of [MnII 4MnIII 16O10(OH)6(OCH3)24(CH3OH)4]6+ serve as eight-connecting nodes, whereas TCNQF4 2− ligands act as four-connecting nodes in a 3D network that has the same topology as fluorite. Compound 3 exhibits an exceptionally high super-catalytic activity for the electron-transfer reaction between ferricyanide and thiosulfate ions in aqueous media.

Original languageEnglish
Pages (from-to)24-34
Number of pages11
JournalChemPlusChem
Volume83
Issue number1
DOIs
Publication statusPublished - 1 Jan 2018

Keywords

  • cluster compounds
  • electron transfer
  • heterogeneous catalysis
  • manganese
  • structure elucidation

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