Isolable Triradical Trication of Hexaaza[1₆]paracyclophane with Embedded 9,10-Anthrylenes: A Frustrated Three-Spin System

Abstract

A new derivative of hexaaza[1 6 ]paracyclophane in which p -phenylenes are alternately replaced by 9,10-anthrylenes was prepared to investigate the impact on overall π-conjugation as well as conformational change of the macrocycle. The charge and spin distribution for one-electron and three-electron oxidation of the macrocycle was elucidated by means of electrochemical, spectroelectrochemical, EPR spectroscopic, and SQUID magnetometric methods. In particular, the triradical trication was successfully isolated as an air-stable salt, and moreover, its structure was disclosed by X-ray analysis. The triradical trication was characterized as a spin-frustrated three-spin system with the antiferromagnetic exchange interaction ( J / k B ≃ – 74 K).