A supramolecular switch between ground high- and low-spin states using 2,2 ':6 ',2 ''-terpyridine-6,6 ''-diyl bis(tert-butyl nitroxide)

Biradical 2,2':6',2 ''-terpyridine-6,6 ''-diyl bis(tert-butyl nitroxide) (tpybNO) showed intramolecular ferromagnetic coupling with 2J/k(B) = +2.14(10) K and its complex [Zn(tpybNO)(MeOH)(2)](BF4)(2) exhibited intramolecular antiferromagnetic coupling with 2J/k(B) = -7.5(4) K, suggesting exchange coupling switchable by means of supramolecular chemistry.