Alkyl Chains Modulated Magnetization Dynamics of Mononuclear Trigonal Prismatic Co^II Complexes

Four benzeneboron-capped mononuclear Co^II complexes with different alkyl substitutions on the fourth position of phenylboronic acid were obtained. The Co^II ions are all wrapped by the pocket-like ligands and located in trigonal prismatic coordination geometries. Alternating-current magnetic susceptibility measurements reveal that they show different magnetization dynamics, such as distinct relaxation rates at the same temperature, the faster QTM rates for the ethyl and propyl substituted complexes, as well as different relaxation processes. Magneto-structural correlation study reveals that the various deviations of coordination geometry of Co^II ion, diverse crystal packings and possible different vibration modes of substituents caused by modifying alkyl chains are the key factors affecting the magnetization dynamics. This work demonstrates that the alkyl chains even locating far away from the metal center can have a large impact on the magnetic behavior of the Co^II complex with a very rigid coordination geometry, offering a new perspective towards transition metal based single-molecule magnets.