Structural and Magnetic Study of O2 Molecules Arranged along a Channel in a Flexible Single-Crystal Host Family

We report the magnetic behaviors of O-2 molecules, which aligned in the channels of four types of single-crystal adsorbents, [M-2(bza)(4)(PYZ)](n) (bza = benzoate; pyz = pyrazine; M = Rh-II (1a) and Cu-II (1b)) and [M-2(bza)(4)(2-mpyz)](n) (2-mpyz = 2-methylpyrazine; M = Rh-II (2a) and Cull (2b)). The X-ray single-crystal structures at various temperatures from 10 to 298 K were determined for O-2-included crystals of la and 2a. All adsorbed O-2 molecules exhibited abnormal magnetic phases above 4 T in the temperature range around 55-105 K. The magnetic behaviors of adsorbed O-2 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 O-2 aggregates involving transformation which is supported by the surrounding of the channels of the single-crystal hosts under the applied magnetic field.