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Highly electron deficient tetrabenzoquinone-appended Ni(II) and Cu(II) porphyrins: spectral, solvatochromatic, electrochemical redox and tuneable F and CN sensing properties

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Abstract

Copper(II) or Nickel(II) complexes of 5,10,15,20-tetrakis(3,4-dioxo-5-t-butylcyclohexa-1,5-dienyl)porphyrin (diOxPM, M = Ni, Cu) exhibited a hypsochromic shift in the B-band as compared to the respective 5,10,15,20-tetrakis(3,5-di-t-butyl-4′-hydroxyphenyl)porphyrin (H2-dtBTPP) and meso-tetrakis(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadienylidene)porphyrinogen (OxP). Thorough investigation of the electrochemical properties of diOxPM (M = Ni, Cu), OxP and H2-dtBTPP lead us to the important observation that the first reduction of diOxPM (M = Ni and Cu) is very much anodically shifted (ΔEredn = 1.1 V) as compared to that of M-dtBTPP (M = Cu or Ni) due to the presence of the strongly electron withdrawing cyclohexadienyl groups. These electron-deficient meso-tetrakis(3,4-benzoquinone)-substituted Ni(II) and Cu(II) porphyrins exhibited very high binding constants (1.5 × 109–2.5 × 107 M−2) with F and CN and can be used to distinguish them from other anions by UV-Vis spectrophotometry. Solvatochromism was combined with anion binding in an attempt to provide the axial ligation mechanism of CN and F ions. These highly electron deficient porphyrins act as F and CN chemosensors in nonaqueous media. However, these porphyrins detect only CN ions in an aqueous medium but remain insensitive towards F ions due to high solvation of F ions in water.

Graphical abstract: Highly electron deficient tetrabenzoquinone-appended Ni(ii) and Cu(ii) porphyrins: spectral, solvatochromatic, electrochemical redox and tuneable F− and CN− sensing properties

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Publication details

The article was received on 27 May 2017, accepted on 18 Aug 2017 and first published on 21 Aug 2017


Article type: Paper
DOI: 10.1039/C7NJ01866E
Citation: New J. Chem., 2017, Advance Article
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    Highly electron deficient tetrabenzoquinone-appended Ni(II) and Cu(II) porphyrins: spectral, solvatochromatic, electrochemical redox and tuneable F and CN sensing properties

    P. Rathi, M. K. Chahal and M. Sankar, New J. Chem., 2017, Advance Article , DOI: 10.1039/C7NJ01866E

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