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      https://www.ias.ac.in/article/fulltext/jcsc/123/06/0827-0837

    • Keywords

       

      Molecular spin; phenolate complex; spin density calculation; structure elucidation.

    • Abstract

       

      Synthesis, structure and properties of new five-coordinate phenolate complexes of di-iron(III) bisporphyrin are reported here, in which phenol binds in $\eta^1$-fashion as an axial ligand. The solid and solution EPR at 120K and 1H NMR spectral pattern in solution provide unequivocal evidence for the high spin (S = 5/2) nature of the complex. Mulliken spin density calculation using DFT demonstrates the positive spin densities at the meso carbons and negative spin densities at the methylene carbons and, as a result, the meso and methylene protons are shifted in the upfield and down field regions, respectively in the 1H NMR spectra of the molecule. Also, the ortho- and para-protons of the phenolate ligands are observed to be shifted in the upfield region while meta-protons are shifted downfield. The alternating shift pattern, which is the opposite sign of the chemical shifts for meta-versus ortho- and para-protons, was also explained due to negative and positive spin densities, respectively on the carbons and indicative of 𝜋 spin delocalization on the phenolate ligand. Thus, the calculated spin density maps accounted for the essential 1H NMR spectroscopic features that are observed here for the phenolate complexes of di-iron(III) bisporphyrin. The temperature dependence of the signals follows the Curie law which is indicative of single spin state throughout the temperature range of −40 to +40°C. The single crystal X-ray structure of the corresponding chloro derivative, trans 1,2-bis(chloroiron(III) octaethyl porphyrinyl)ethene, has also been reported here which authenticates the high-spin nature of the complex.

    • Author Affiliations

       

      Susovan Bhowmik1 Debangsu Sil1 Ranjan Patra1 Sankar Prasad Rath1

      1. Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
    • Dates

       
  • Journal of Chemical Sciences | News

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