Stable meta- and para-phenylene bridged porphyrin meso-oxy radical dimers and their NiII and ZnII complexes were synthesized. All the dimers exhibited optical and electrochemical properties similar to the corresponding porphyrin meso-oxy radical monomers, indicating small electronic interaction between the two spins. Intramolecular spin-spin interaction through the π-spacer was determined to be J/kB =-15.9 K for m-phenylene bridged ZnII porphyrin dimer. The observed weak antiferromagnetic interaction has been attributed to less effective conjugation between the porphyrin radical and linking π-spacer due to large dihedral angle. In the case of ZnII complexes, both para- and meta-phenylene bridged dimers formed 1D-chain in solutions and in the solid states through Zn-O coordination.
Keywords: EPR; Magneticity; Porphyrins; Radicals; SQUID.
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