Syntheses, structures, and magnetic properties of terephthalato bridged dinuclear copper(II) and manganese(II) complexes with a tetradentate N-donor Schiff base

Three dinuclear compounds of the types [Cu2(L)2(μ-tp)](ClO4/PF6)2 (1/2) and [Mn2(L)2(μ-tp)](ClO4)2 H2O (3) [L = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,3-propanediamine and tp = terephthalate dianion] have been synthesized and characterized. Structures of 1–3 are solved using single crystal X-ray diffraction measurements. The structural analyses show bis(monodentate) in 1/2 and bis(bidentate) in 3 of terephthalate bridging motifs resulting dicationic dinuclear unit [M2(L)2(μ-tp)]2+ [M = Cu (1/2) and Mn (3)]. Each metal center adopts distorted trigonal bipyramidal geometry in 1/2 and a distorted octahedral geometry in 3 with MN4O and MN4O2 chromophores, respectively. Chelation by the tetradentate Schiff base along with bis(monodentate) and bis(bidentate) bridging of terephthalate complete pentacoordination around each copper(II) center in 1/2 and hexacoordination around each manganese(II) center in 3, respectively. Variable-temperature magnetic susceptibility measurements of 1–3 in the 2–300 K temperature range reveal weak antiferromagnetic interaction presumably due to long bridging arm.

Graphical abstractSyntheses, crystal structures and magnetic behaviours of two dinuclear copper(II) and one dinuclear manganese(II) terephthalate complexes with a tetradentate N-donor Schiff base (L) described. Interesting variation of bridging motifs of tp from bis(monodentate) to bis(bidentate) is revealed through change of the metal ions from copper(II) to manganese(II) observed. Variable-temperature magnetic susceptibility measurements show weak antiferromagnetic coupling between the metal centers mediated through long tp bridging.Figure optionsDownload full-size imageDownload as PowerPoint slide