Supramolecular Isomerism in Coordination Polymers of Isophthalato‐Bridged Mn II 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)(H 2 O) 2 ] · (dpyo) · (H 2 O)} n (colorless) ( 1 ) and {[Mn(isop)(H 2 O)(dpyo) 0.5 ] · (dpyo) 0.5 · (H 2 O) 2 } n (pink) ( 2 ). Both isomers crystallize in the same crystal system (triclinic) and space group ( P $\bar {1}$ ). The structural determination of 1 reveals an isophthalato‐bridged 1D coordination polymer, {[Mn(isop)(H 2 O) 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 π‐π 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 × 10 –5 for 1 and J = –1.06 ± 0.03 cm –1 , g = 2.01 ± 0.01 and R = 2.8 × 10 –5 for 2 .(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)