Syntheses, crystal structures and magnetic studies of new 2D coordination polymers containing dinuclear manganese(II) repetitive units using a ditopic isonicotinhydrazone based N,N,O-donor ligand

Abstract

Three new complexes of manganese(II) with pseudohalide anions and (E)-N′-(phenyl(pyridin-2-yl)methylene)isonicotinhydrazide (HL), namely a 2D polymer with azide bridged dinuclear unit [Mn2(L)2(μ-N3)2]n (1), a 2D coordination polymer [Mn2(L)2(NCS)2]n (2a) and a monomeric [Mn(HL)(NCS)2(OHCH3)] (2b), were synthesized and characterized by elemental analyses and spectroscopic methods. The structures were established by X-ray diffraction, and further studied by magnetic susceptibility measurements. The isonicotinhydrazide ligand acts as a mononegative tetradentate N3O-donor ligand and coordinates to the manganese center in the enolic form (N–NC–O) in 1 and 2a while in complex 2b coordinates as NNO-donor tridentate neutral ligand in keto form (N–NH–CO). Two bridging azide ligands connect the two metal centers in an end-on (EO) fashion in 1. For complex 2a the enolic oxygen of the hydrazone moiety spans two metal centers to form a dinuclear unit containing Mn2O2 four-membered planar ring. Magnetic measurements revealed antiferromagnetic coupling inside the dimers for 1 and ferromagnetic coupling for 2a.