Three cyano-coordinated cobalt porphyrin dimers were synthesized and thoroughly characterized. The X-ray structure of the complexes reveals that cyanide binds in a terminal fashion in both the and isomers of ethane- and ethylene-bridged cobalt porphyrin dimers, while in the ethylene-bridged dimer, cyanides bind in both terminal and bridging modes. The nonconjugated ethane-bridged complex stabilizes exclusively a diamagnetic metal-centered oxidation of type Co(por)(CN) both in the solid and in solution. In contrast, the complexes with the conjugated ethylene-bridge contain signatures of both paramagnetic ligand-centered oxidation of the type Co(por)(CN) and diamagnetic metal-centered oxidation of type Co(por)(CN) with the metal-centered oxidized species being the major component in the solid state as observed in XPS, while the ligand-centered oxidized species are present in a significant amount in solution. H NMR spectrum in solution displays two set of signals corresponding to the simultaneous presence of both the diamagnetic and paramagnetic species. EPR and magnetic investigation reveal that there is a moderate ferromagnetic coupling between the unpaired electrons of the low-spin Co center and the porphyrin π-cation radical in Co(por)(CN) species as well as an antiferromagnetic coupling between the two Co(por) units through the ethylene and CN bridges.

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http://dx.doi.org/10.1021/acs.inorgchem.4c01150DOI Listing

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