Supramolecular isomerism in coordination polymers of isophthalato-bridged MnII complexes using 4,4'-dipyridyl N,N′-dioxide

A one-pot reaction of three components [Mn-II, isophthalate dianion (isop) and 4,4'-dipyridyl N,N'-dioxide (dpyo)] in water/methanol (1:1) causes self-assembly resulting in two 3D supramolecular isomers of the same stoichiometry, {[Mn(isop)(H2O)(2)]center dot(dpyo)center dot(H2O)}(n) (colorless) (1) and {[Mn(isop)(H2O)(dpyo)(0.5)]center dot(dpyo)(0.5)center dot(H2O)(2)}(n) (pink) (2). Both isomers crystallize in the same crystal system (triclinic) and space group (P (1) over bar). The structural determination of 1 reveals an isophthalato-bridged 1D coordination polymer, {[Mn(isop)(H2O)(2)](n), having 16- and 8-membered rings where isophthalate acts simultaneously as chelating and bridging ligand connected to three metal centers. In isomer 2 the 1D chains transform to a 2D arrangement through bridging dpyo that replaces a water molecule at metal axial position. Both the crystal structures result in a 3D supramolecular network achieved through H-bonding among the 1D (in 1) or 2D (in 2) coordination polymers with lattice water and dpyo molecules and also by means of pi-pi interactions in 1. Low-temperature magnetic measurement indicates antiferromagnetic interaction in both the isomers and the best fits are given by the exchange parameters J = -0.56 +/- 0.02 cm(-1), g = 2.01 +/- 0.01 and R = 3.1 x 10(-5) for 1 and J = -1.06 +/- 0.03 cm(-1), g = 2.01 +/- 0.01 and R = 2.8 x 10(-5) for 2. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).