Preparation, Crystal Structure, and Magnetic Properties of an Oligonuclear Complex with 12 Coupled Spins and an S=12 Ground State

Article abstract of DOI:10.1021/ja00217a017

A novel oligonuclear compound, containing six manganese(II) ions and six nitronyl-nitroxide radicals NITPh (NITPh = 2-phenyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl 3-oxide), 6, was synthesized, and its crystal structure, magnetic properties, and EPR spectra are reported.This cyclohexamer crystallizes in the trigonal system, space group <*>, with rhombohedral axes a = b = c = 21.21(1) Angstroem, α = β = γ =116.77(2)^o, and Z = 6.The structure consists of discrete clusters of six radicals and six Mn(hfac)2, in which each transition-metal ion is in a distorted octahedral environment.Two oxygen atoms belonging to two different nitronyl-nitroxide radical ligands occupy two cis coordination positions around manganese.The temperature depndence of the magnetic susceptibility in the range 300-5 K indicates that the manganese(II) and the radical spin are antiferromagnetically coupled to give an S = 12 ground state.The single-crystal EPR spectra of 6 show both M = 1 and M = 2 transitions.The angular dependence of the line width, which is similar to that of typical one-dimensional materials, is discussed within a model considering the zero-field splitting tensors of the populated spin multiplets.