In previous work, we have shown that going from the mononuclear [Co(bmsab)] 2 -to the radicalbridged dinuclear complex [{Co(H 2 tmsab)]} 2 (µ-tmsab)] 3 -slows down the relaxation rate by a factor of up to 350. Here bmsab is the dianion of 1,2-bis(methanesulfonamide) benzene and tmsab is the tetraanion of 1,2,4,5-tetrakis(methanesulfonamide)benzene. Fits of the magnetic data suggested the presence of both strong local ZFS, as well as strong exchange interactions. However, the complex could only be obtained through "crystal picking", resulting in extremely low yields.