Unexpected diversity and novel features within a family of new azide-bridged MnIIcomplexes of pyridyl/imineligands

Abstract

A family of tetradentate ligands, [N,N′-bis(pyridine-2-yl)]ethane-1,2-diamine (L1), [N,N′-bis(pyridine-2-yl)]propane-1,3-diamine (L2) and [N,N′-bis(pyridine-2-yl)]butane-1,4-diamine (L3) has been prepared. These ligands differ only in the number of CH2 groups separating two pyridyl/imine moieties, however, in reactions with MnII and N−3 salts, they produce structurally very diverse solids; [Mn2(L1)3(N3)]n(ClO4)3n (1), [Mn2(L2)2(N3)2](PF6)2 (2) and [Mn2(L3)(N3)2]n(ClO4)2n (3). Complexes 1, 2 and 3 consist of azido-bridged magnetically dilute Mn2 pairs, arranged as 1-D, discrete and 2-D arrays, respectively. In these materials, the connection between Mn centers within the dinuclear entities occurs through mono-1,3-N−3, bis-1,3-N−3 and bis-1,1-N−3 bridges, respectively, for 1, 2 and 3. Bulk magnetic measurements reveal that the coupling within such units is antiferromagnetic (J = −1.8 cm−1, 1; J = −4.8 cm−1, 2) and ferromagnetic (J = +1.45 cm−1, 3), depending on whether the N−3 binding mode is end-to-end (EE) or end-on (EO). The reported values are given according to the convention H = −2JS1S2 for the spin-Hamiltonian.