Magnetic Spin States of O₂ Confined in a Graphitic Slit-Shaped Nanospace at Low Temperature

Abstract

The magnetic susceptibility of O 2 molecules confined in slit-shaped graphitic micropore systems with the slit pore width w of 0.75, 0.96, and 1.45 nm was measured at diffrent coverages F and over the temperature range of 1.7-100 K. For all micropore systems, the adsorbed O 2 at a very low coverage showed the paramagnetism without any obvious magnetic transition, which is quite close to the paramagnetism of bulk gaseous oxygen. An antiferromagnetic behavior appeared with an increase in F. This behavior was caused not by the formation of 2D lattices or bulk solid phases but by the random magnetism for the systems of w ) 0.75 and 0.96 nm. The random magnetism indicates the cluster formation of the O 2 molecules in the nanospace. The paramagnetism and the random magnetism arise from an enhanced intermolecular interaction of O 2 in the unique potential field of the narrow slit space. The O 2 assembly in the micropores showed a different magnetic behavior dpending on the pore width. Besides the cluster formation, a phase like the θ phase, which appears in the O 2 bilayer on the 2D graphite surface, was observed for 0.4 < F < 0.8 in the micropores of w ) 1.45 nm. This suggest that the micropores with w ) 1.45 nm provide an enhanced formation of the specific 2D phase. These unusual magnetic behaviors were presumed to be caused by the special critical phenomenon in the nanospace.

Bioinorganic transformations of liver iron deposits observed by tissue magnetic characterisation in a rat model

“…The measurements on the freeze-dried livers were performed by directly placing the powders into gelatine capsules, while the liquid suspension of ferritin was introduced into ESR-grade quartz tubes. In order to assure the absence of any magnetic contribution coming from adsorbed oxygen in the samples, repeated runs above and below its boiling temperature were used in the measurements of each sample [20,31]. These precautions made it increase the duration of the magnetic experiment up to typically 10 h per sample.…”

Functional Porous Coordination Polymers

“…128, 229, 292, 310, 318, 398 O 2 and NO are among the smallest stable paramagnetic molecules under ambient conditions and have the potential to form new molecular‐based magnetic and dielectric materials. However, many attempts to form 1D arrays of these paramagnetic gas molecules through confinement of the molecules in porous coordination polymers399 as well as carbon materials400, 401 were not successful. Unlike aromatic and polar molecules which can take part in intermolecular interactions, such as π–π stacking and hydrogen bonding, these simple molecules can only enter into weak van der Waals force interactions which are not strong enough to form 1D assemblies.…”

Chemistry of coordination space of porous coordination polymers

“…O 2 and NO are among the smallest stable paramagnetic molecules under ambient conditions and have the potential to form new molecular-based magnetic and/or dielectric materials. However, we were not successful in many attempts to form 1D arrays of these paramagnetic gas molecules through confinement of the molecules in porous coordination polymers [68] or in microporous carbon materials [57,69]. Therefore, to form a regular assembly of these simple molecules in a nanochannel, it is important that we use not only the strong confinement effect of nanospace but also the commensurability between the host structure and guest molecule mentioned above, the amount adsorbed in each unit pore of CPL-1 shows precisely integral value [46,47].…”