Synthesis, structural characterization and magnetic properties of mixed-valent bis-bipyridine manganese carboxylate clusters

Abstract Procedures have been developed for the synthesis of complexes containing the cations [Mn 4 O 2 (O 2 CR) 4 (L) 2 ] 2+ (R=Me, Et, Ph) ( 1 ) and [Mn 4 O 2 (MeO) 3 (O 2 CPh) 2 (L) 2 (MeOH)] 2+ ( 2 ). Treatment of the corresponding [Mn 3 O(O 2 CR) 6 (py) 3 ](ClO 4 ) complex with the ligand 1,2-bis(bipyridine-6′-yl)ethane (L) in MeCN or MeOH leads to the formation of 1 and 2 , respectively. Both complexes contain [Mn 4 O 2 ] cores. Complex 1 has overall antiferromagnetic coupling resulting in a S =1 spin ground state. The metal centers in the core of complex 2 are also antiferromagnetically coupled, but in this case the spin ground state is S =7/2. Complex 2 also displays an out of phase signal in the ac magnetic susceptibility study, indicating it to be a new example of single molecule magnet (SMM).