Magnetic behaviour of the ferrimagnetic ((1)over-bar/2,5/2,(1)over-bar/2) linear trimer in complexes of Mn(hfac)(2) with bis- and trisnitroxide radicals

Characterisation and magnetic properties of new metal-radical complexes wit h bivalent Mn having a general formula {[Mn(hfac)(2)](m)(R)(n)} are given. In these complexes, the aminoxyl radicals have magnetic, triplet or quartet , ground state and form with Mn2+ heterospin structures. They show 1D, 2D a nd 3D behaviour depending on the crystal structure, chemical formula and mo lecular structure of radical. In the ordered state, the complexes form a fe rrimagnetic structure due to a strong negative coupling between the radical and Mn spins. Magnetic anisotropy in some single crystals was studied. The 3D complex {[Mn(hfac)(2)](3)(3R(T))(2)} with a linear triradical can be de scribed within a sublattice model of ferrimagnetism, one sublattice of whic h is formed by 1D chains, while the other consists of magnetically isolated Mn2+ ions. Its comparatively high T-C = 45 K is accounted for the large in terchain exchange interaction (3.9 K) through the isolated Mn2+. Analysis of their paramagnetic properties shows that the higher energy exci tations are related to the desintegration of the ferrimagnetic ((1) over ba r/2, 5/2,(1) over bar/2) linear trimer species, which can be isolated in al l these compounds.