Paramagnetic Semiconductors: Hybrid Molecular Materials Based on Ethyl- and Methyl-pyridinium-Substituted Verdazyl Radical Cations and the Ni(dmit)2 Anion (dmit = 1,3-Dithiol-2-thione-4,5-dithiolate)

Abstract

Abstract Four kinds of 1:1 salts of 3-(4- and 3-alkyl-pyridinium)-1,5-diphenylverdazyl (alkyl = ethyl and methyl) radical cations with the Ni(dmit)2 anion ([p-EtPyDV]+[Ni(dmit)2]− (1), [m-EtPyDV]+[Ni(dmit)2]− (2), [p-MePyDV]+[Ni(dmit)2]− (3), and [m-MePyDV]+[Ni(dmit)2]− (4)) have been prepared. The magnetic properties of salts 1–4 were discussed based on the results obtained by magnetic susceptibility and ESR measurements of 1–4 and the crystal structure analysis of 1. The results of the crystal structure analysis of salt 1 indicate the dimer formation in Ni(dmit)2 anion molecules, and the dimers are sandwiched between two verdazyl cations [p-EtPyDV]+, indicating the formation of a magnetic linear tetramer in 1. The magnetic susceptibility data for salt 1 have been fitted to a four-spin linear tetramer model using an end exchange interaction of 2J1/kB = −780 K and a central interaction of 2J2/kB = −200 K. The conductivity (σ) of salts 1, 2, 3, and 4 at room temperature was σ = 2.3 × 10−5, 1.8 × 10−4, 1.4 × 10−5, and 5.4 × 10−6 S cm−1 with an activation energy of EA = 0.28, 0.52, 0.21, and 0.33 eV, respectively. The 1:1 salts 1–4 are new molecular paramagnetic semiconductors.