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

Abstract

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(μ_1,1-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(μ_1,3-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.