Preparation, crystal structure, and magnetic properties of an oligonuclear complex with 12 coupled spins and an S = 12 ground state

Abstract

A novel oligonuclear compound, containing six manganese( 11) ions and six nitronyl-nitroxide radicals NITPh (NITPh\n= 2-phenyl-4,4,5,5-tetramethyl-4,5-dihydr1oH- -imidazolyl- 1- oxy1 3-oxide), [Mn(hfac),NITPh],, was synthesized, and its crystal\nstructure, magnetic properties, and EPR spectra are reported. This cyclohexamer crystallizes in the trigonal system, space\ngroup R3, with rhombohedral axes a = b = c = 21.21 (1) A, a = p = y = 116.77 (2)O, and Z = 6. The structure consists\nof discrete clusters of six radicals and six Mn ( h f a ~ )in~ ,w hich each transition-metal ion is in a distorted octahedral environment.\nTwo oxygen atoms belonging to two different nitronyl-nitroxide radical ligands occupy two cis coordination positions around\nmanganese. The temperature dependence of the magnetic susceptibility in the range 300-5 K indicates that the manganese(I1)\nand the radical spins are antiferromagnetically coupled to give an S = 12 ground state. The single-crystal EPR spectra of\n[Mn ( h f a ~ ) ~N1TPshho]w~ both M = 1 and M = 2 transitions. The angular dependence of the line width, which is similar\nto that of typical onedimensional materials, is discussed within a model considering the zero-field splitting tensors of the populated\nspin multiplets.