A hydrocarbon hexaradical with three localized 1,3-cyclopentanediyl triplet diradicals linked by 1,3,5-trimethylenebenzene as ferromagnetic coupler: Synthesis of the azoalkane precursor, photochemical generation of the polyradical, and EPR characterization of its septet-spin ground state

The unknown trisazoalkane 3 was prepared and photodenitrogenated into the novel septet hexaradical H-3, which is composed of three localized 1,3-cyclopentanediyl triplet diradicals as spin carriers, connected to the cross-conjugated ferromagnetic coupler 1,3,5-trimethylenebenzene. On nitrogen extrusion during the UV photolysis of the trisazoalkane 3 in the toluene matrix at 77 K, the characteristic triplet, quintet, and septet EPR signals for the corresponding diradical D-3, tetraradical T-3, and hexaradical H-3 were observed, all persistent for months at 77 K. Computer simulation of the EPR signals for the hexaradical gave the zero-field parameters D = 0.00907 cm(-1) and E = 0.000187 cm(-1), which is in good agreement with related polyradicals.