catena-Poly[[[bis(2,2′-bipyridine)manganese(II)]-μ4-3,3′-sulfanediyldipropionato] bis(perchlorate)]

The title compound, [Mn2(C6H8O4S)(C10H8N2)4](ClO4)2, which was crystallized from an aqueous solution, features two MnII atoms in the asymmetric unit, each being coordinated by four N-atom donors from 2,2′-bipyridine ligands and two O atoms of two different 3,3′-sulfanediyldipropionate (L) ligands, with the O atoms in cis positions. The two carboxylate groups of each L ligand, which adopt a syn-anti coordination mode, combine with four MnII atoms, yielding one-dimensional chains extending along [010].

The author thanks the Natural Science Foundation of Jiangsu for financial support.

Comment
In recent years, a great deal of effort has been devoted to metal-organic coordination polymers owning to their structures and potential applications. (Gardner et al., 1995;Seo et al., 2000;) Many ligands including rigid carboxylate arms have been used in the design of metal-organic materials with desired topologies (Cao et al., 2002;Xu et al., 2005). Compared to rigid carboxylate arms, relative fewer complexes have been reported derived from flexible carboxylate arms (Cao et al., 2004;Yong et al., 2004). We know that the formation of crystal structure is sensitive to the flexibility of carboxylate arms, and such flexibility may increase the probability of making tube-like or cage-like structure. Herein, in the course of ongoing studies on the exploration on carboxylate ligand with flexible carboxylate arms, we choose a multi-carboxylate ligand, namely 3,3'-thiodipropionic acid, which can act not only as chelating ligand, but also as bridging ligand, to assemble new coordination polymers. In this contribution, in the hope of obtaining a supramolecular complex, we used 3,3'-thiodipropionic acid reacting with manganese salts as well as 2,2'-bipyridine ligands and synthesized a new one-dimensional complex. Here, we report the preperation and X-ray characterization of the complex, namely (Mn 2 L(bpy) 4 ).(ClO 4 ) 2 .
The molecular structure of the complex is depicted in Figure 1. In the complex, the local coordination of the manganese atom are defined by four nitrogen donors from bpy ligands with Mn···N distance from 2.236 (2) to 2.293 (2)Å and by two oxygen atoms of different L ligands with Mn···O distance from 2.124 (2) to 2.121 (6) Å, yielding a distorted octahedral geometry. Two carboxylic groups of each L ligand, which adopt syn-anti coordination mode, combine with four manganese(II) atoms to form a one-dimensional chain (shown in Figure 2). The distance of two manganese(II) atom bridged by L ligand is 4.7693 Å. Figure 3 shows the molecular packing diagram of the complex viewed in the ac plane. In the complex, two carboxylic groups and the sulfur atom of each L ligand adopt syn-anti conformation to debase the steric hindrance.

Experimental
A solution of Mn(ClO 4 ) 2.(H 2 O) 6 (0.365 g, 1 mmol) was slowly added to a mixture of L ligand (0.180 g, 1 mmol) and NaOH (0.040 g, 1 mmol) in water (10 ml) with stirring under heating. Then a solution of bpy (0.198 g, 1 mmol) in ethanol (5 ml) was dropped into the mixture. The resulting solution was continued with stirring for another 2 h under heating and filtered when cooled to room temperature. The yellow crystals suitable for X-ray crystallographic analysis were obtained after a week.

Refinement
Crystals of the title complex are triclinic, space group P-1. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were visible in difference maps and were subsequently treated as riding atoms with distances restraints of C-H = 0.97 (CH 2 ) or 0.93Å (CH). Fig. 1. The asymmetric unit of the title compound, showing the atom-labelling scheme. For the sake of clarity, hydrogen atoms have been omitted.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.