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Download fileLigand Noninnocence in Cobalt Dipyrrin–Bisphenols: Spectroscopic, Electrochemical, and Theoretical Insights Indicating an Emerging Analogy with Corroles
journal contribution
posted on 17.01.2019, 17:51 authored by Wenqian Shan, Nicolas Desbois, Sandrine Pacquelet, Stéphane Brandès, Yoann Rousselin, Jeanet Conradie, Abhik Ghosh, Claude P. Gros, Karl M. KadishThree cobalt dipyrrin–bisphenol
(DPPCo) complexes with different meso-aryl groups
(pentafluorophenyl, phenyl, and mesityl) were synthesized and characterized
based on their electrochemistry and spectroscopic properties in nonaqueous
media. Each DPPCo undergoes multiple oxidations and reductions with
the potentials, reversibility, and number of processes depending on
the specific solution conditions, the specific macrocyclic substituents,
and the type and number of axially coordinated ligands on the central
cobalt ion. Theoretical calculations of the compounds with different
coordination numbers are given in the current study in order to elucidate
the cobalt-ion oxidation state and the innocence or noninnocence of
the macrocyclic ligand as a function of the changes in the solvent
properties and degree of axial coordination. Electron paramagnetic
resonance spectra of the compounds are obtained to experimentally
assess the electron spin state. An X-ray structure of the six-coordinate
complex is also presented. The investigated chemical properties of
DPPCo compounds under different solution conditions are compared to
those of cobalt corroles, where the macrocycle and metal ion also
possess formal 3– and 3+ oxidation states in their air-stable
forms.