Syntheses, structures and magnetic properties of azido- and phenoxo-bridged complexes of manganese containing tridentate aroylhydrazone based ligands

Five new compounds have been prepared by the reaction of MnCl2·4H2O with aroylhydrazone in the presence of NaN3: [Mn(L1)(N3)(HOCH3)]2 (1), [Mn(L2)(N3)(HOCH3)]2 (2), [Mn(L3)(N3)(HOCH3)0.75(EtOH)0.25]2 (3), [Mn(L4)(N3)(HOCH3)]2 (4) and [Mn2(L2)2(HOCH3)2]n (5). (HL1 = (E)-3-hydroxy-N′-(1-(pyridin-2-yl)ethylidene)-2-naphthohydrazide, HL2 = (E)-N′-(phenyl(pyridin-2-yl)methylene)furan-2-carbohydrazide, H2L3 = (Z)-N′-(4-oxo-4-phenylbut-2-en-2-yl)isonicotinohydrazide, H2L4 = (E)-N′-(5-bromo-2-hydroxybenzylidene)isonicotinohydrazide). In absence of NaN3 the mononuclear complex [Mn(H2L5)2(EtOH)2Cl2] (6) was obtained by the reaction of MnCl2·4H2O and H2L5 ((E)-N′-(2-hydroxy-3-methoxybenzylidene)isonicotinohydrazide). All the compounds have been characterized by elemental analyses, IR spectra, single crystal X-ray diffraction and magnetic susceptibility measurements. Compound 6 exhibits mononuclear structure, 1–4 dinuclear structure whereas complex 5 yields two-dimensional sheets parallel to the (1 0 0) plane in which the deprotonated H2L4 act as bridging ligand. The magnetic study reveals dominating antiferromagnetic interactions in 1 and 5 whereas the ferromagnetic coupling dominates in 2–4. The magnetic properties are interpreted in terms of the electronic structure of the Mn ions and structural parameters.

Graphical abstractFour new, dinuclear, azido bridged complexes of Mn(II) and Mn(III) were prepared. Presence of the azide in a suitable ratio and its absence were resulted in a two-dimensional phenoxo bridged coordination polymer and a mononuclear complex of Mn(II), respectively. Both ferromagnetic and antiferromagnetic coupling via end-on bridging azide are seen.Figure optionsDownload full-size imageDownload as PowerPoint slide