Magnetic Properties and Crystal Structures of 1,5-Diphenylverdazyls with Electron Acceptor Groups in the 3-Position

The magnetic properties of four diphenylverdazyls (2−5) with electron acceptor groups in the 3-position were studied by measuring the magnetic susceptibility and heat capacity. The crystal structures of 3 and 4 were determined, and for 2 the crystal structure analysis led to an improved refinement. Verdazyl 2 was found to be an antiferromagnet with a Neel temperature of TN = 1.16 ± 0.04 K. Above the transition temperature TN, 2 behaves as a quasi-one-dimensional Heisenberg ferromagnet with the intrachain exchange interaction of 2J/kB = +7.0 ± 1.0 K. The interchain exchange interaction zJ‘/kB was estimated to be −1.5 ± 0.2 K, where z is the number of interchain bonds per spin. On the other hand, 3 and 5 behave as 1D nonalternating and alternating Heisenberg antiferromagnets with an exchange interaction of 2J/kB = −11.6 K and 2J1/kB = −113 K (alternation parameter α = J2/J1 = 0.4), respectively. The susceptibility of 4 follows the Curie−Weiss law with a negative Weiss constant of −18 K above 100 K. Below 10...