Structure, magnetic properties and spin density of two alternative Mn(II) coordination polymers based on 1,4-bis(2'-carboxyphenoxy)benzene.

Two novel manganese coordination polymers [Mn2(μ2-bcpb)(μ4-bcpb)(2,2'-bipy)2]n (1) and [Mn2(μ3-bcpb)2(2,2'-bipy)2(H2O)]n (2) (H2bcpb = 1,4-bis(2'-carboxylato phenoxy)-benzene; 2,2'-bipy = 2,2'-bipyridine), have been synthesized successfully from the same reactants. This unusual selectivity was corroborated by X-ray powder diffraction. Single crystal X-ray diffraction analysis of complex 1 reveals that neighboring Mn(II) ions are linked via two bcpb2- anions to form a dinuclear Mn(II) subunit [Mn2(μ1,1-COO)2]2+ with a Mn⋯Mn distance of 3.3758 (6) Å. And π⋯π interactions between aromatic rings of the bcpb2- and 2,2'-bipy ligands stabilize the two-dimensional extended coordination network with the unprecedented Schläfli symbols {4·62}2{42·62·82}. In the [Mn2(μ1,3-COO)2]2+ subunit of 2, two linking bcpb2- ligands subtend an interaction distance of 4.4048(6) Å. Intermolecular O-H⋯O hydrogen bonds involving oxygen atoms of carboxylic acid and coordinated water molecules connect adjacent 1D chain molecules into a 2D network. Experimental temperature-dependent magnetic susceptibility measurements and spin density analyses by DFT disclose that compounds 1 and 2 display different magnetic properties.