Structural and magnetic study of O2 molecules arranged along a channel in a flexible single-crystal host family.

We report the magnetic behaviors of O2 molecules, which aligned in the channels of four types of single-crystal adsorbents, [M2(bza)4(pyz)]n (bza = benzoate; pyz = pyrazine; M = RhII (1a) and CuII (1b)) and [M2(bza)4(2-mpyz)]n (2-mpyz = 2-methylpyrazine; M = RhII (2a) and CuII (2b)). The X-ray single-crystal structures at various temperatures from 10 to 298 K were determined for O2-included crystals of 1a and 2a. All adsorbed O2 molecules exhibited abnormal magnetic phases above 4 T in the temperature range around 55−105 K. The magnetic behaviors of adsorbed O2 molecules between four inclusions were discussed. The existence of the metastable state, which was also suggested by hysteresis on the M−H curves, was revealed by analysis of the time course of the magnetization. Considering that the abnormal magnetic behavior occurred at relatively high temperatures and a low magnetic field, it was suggested that these behaviors were induced because of the changes of magnetic interaction of included O2 aggregates ...