Air-stable diradical dications with ferromagnetic interaction exceeding the thermal energy at room temperature: from a monomer to a dimer

Two tetraazacyclophane dications ( 1 2+ and 2 2+ ) with different remote substituents have been synthesized, isolated and characterized. Their electronic structures and physical property were studied by various spectroscopic techniques, single crystal X-ray diffraction, super conducting quantum interference device (SQUID) measurements and theoretical calculations. The dications have triplet ground states with ferromagnetic interaction exceeding the thermal energy at room temperature. The solid-state structures of these species were tunable by substituent effect, with 1 2+ as a monomer and 2 2+ as a dimer.