Magnetic properties of hexanuclear manganese antiferromagnetic clusters {Mn6}

We report a study of magnetic properties of a series of hexanuclear manganese metallamacrocycles {Mn6}. The magnetic properties are characterized by antiferromagnetic (AFM) coupling constants J1∕kB≈−4.0K, between the nearest neighbors, and J2∕kB≈−1.2K, between the next-nearest neighbors. The temperature dependence of H1 NMR linewidth is observed to be consistent with the AFM singlet ground state with a total spin ST=0. H1 nuclear spin-lattice relaxation rate 1∕T1 shows a strong enhancement at low temperatures with a peak around T≈J1, as commonly observed in AFM molecular rings and clusters.