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In recent years synthesis and properties of metal-coordinated radicals have gained momentum due to their importance in biology. The determination of molecular structure, investigating the magnetic, spectral and redox properties, and correct assignment of electronic structure of metal complexes of 2-anilino-4,6-di-tert-butylphenol-derived ligands in their deprotonated forms have drawn the attention of inorganic chemists due to redox-active nature of such ligands [1]. As a part of our continuing efforts to understand the properties of metal-coordinated ligand radical species from the standpoint of modeling Galactose Oxidase activity [2,3], we have directed our attention to designing new ligands of 2-anilino-4,6-di-tert-butylphenol appended with benzylthioether, ethylthioether, thioalkylpyridines and azo functionality [4,5], to investigate their coordination behavior towards transition metal ions, and to investigate radical coupling-driven reactions.
In this presentation, an account of detailed molecular (X-ray), spectroscopic and magnetic, and reactivity (redox) aspects of a number of ligand radical-coordinated metal complexes involving a group of redox-active ligands to correctly assign the spin-state of the metal and oxidation level of the coordinated ligands will be discussed. Our designed chelating ligands provide bis-phenolate(2−) and phenoxyl(1−) radical, o-amidophenolate(2−), o-iminobenzosemiquinonate(1−) radical and o-benzoquinone forms of the coordinating ligands. The electronic structure of the complexes is then rationalized by the Density Functional Theory (DFT) and Time-Dependent (TD)-DFT calculations, which successfully rationalize the observed properties of the complexes. Radical-driven reactivity aspects (N–N and –O–C–O– bond formation) will also be discussed.
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