論文

A novel purely organic radical, 5-methoxy-2,2-diphenyl-1,2-dihydroquinoline N -oxyl ( 2 ), has been synthesized and structurally characterized in order to examine the substituent effect on the known derivative, 2,2-diphenyl-1,2-dihydroquinoline N -oxyl ( 1 ). Based on SQUID measurement, 2 exhibited a ferromagnetic interaction obeying the Bleaney–Bowers equation with 2 J = +17 cm−1. X-ray analysis revealed that the 5-methoxy substitution induces an offset π-stacking, resulting in ferromagnetic interactions.

Two aromatic nitroxyl radical derivatives of 2,2-diphenyl-1,2-dihydroquinoline N-oxyl (1), namely, 5-[2-(trimethylsilyl)ethynyl]-2,2-diphenyl-1,2-dihydroquinoline N-oxyl (2) and 5-ethynyl-2,2-diphenyl-1,2-dihydroquinoline N-oxyl (3), were synthesized, and their magneto-structural correlation was described in connection with their assembled structures. Single-crystal XRD analysis of 3 revealed a hydrogen bond between the oxygen atom in the nitroxyl group and the terminal hydrogen atom of the ethynyl group with dO⋯(H)C = 3.099(5) Å. SQUID measurements revealed that 3 follows a 1D antiferromagnetic chain model with J = −10.4 cm−1. In contrast, a slight increase in the χMT value to 0.44 emu K mol−1 was observed in 2, with a decreasing temperature indicating the presence of a weak intermolecular ferromagnetic interaction. These magnetic behaviors differ from that of the unsubstituted radical 1.