Three novel coordination polymers have been obtained by the reaction of M(NO 3 ) 2 ·6H 2 O (M = Mn II and Co II ) or FeCl 2 ·4H 2 O with KNCS and DPDS [di(4-pyridyl)disulfi de] l igand, [Mn-(NCS) 2 (DPDS) 2 ] 2 ·DPDS·H 2 O (1), [Fe(NCS) 2 (DPDS) 2 ]·3H 2 O (2), and [Co(NCS) 2 (DPDS) 2 ]·2H 2 O (3). The three complexes exhibit infinite linear chain structures, where the metal ions are connected by double N,N′-DPDS bridges, that are further connected through hydrogen bonding to give pseudo-3D structures which contain channels where solvent and/or free DPDS molecules are located. The number and type of these guest molecules will have a determining influence in the final crystal system and space groups adopted for every compound obtained, which will be analyzed. H-bonding promotes interpenetrated 3D networks in 1− 3. Characterization by IR, UV−vis, X-ray diffraction, ESR spectroscopy, and magnetic measurements is developed. Slight antiferromagnetic interactions are observed, essentially in the Fe(II) and Co(II) compounds, that are associated with the double DPDS bridges.
■ INTRODUCTIONThe quick development in the very recent years of the research on the formerly known 4,4′-dipyridine type of ligands is related to their use in very important present fields of investigation, such as metal organic frameworks (MOFs), 1 coordination polymers (CPs), 2 spin crossover (SCO) systems, 3 and others. These ligands are well-known to be excellent different-size spacers in order to connect chains or sheets, increasing their dimensionality, increasing the structural flexibility, and generating voids of a quadrangular type. The 4,4′-relative position of the N donor atoms provides the extension of these polymers, with the rigidity being a limiting factor for a selfassembly strategy. The design and synthesis of coordination polymers are of great interest for crystal engineering. The structural motifs in the CPs range from zero to threedimensional, and their infinite network topologies are interesting for the development of host−guest functional materials such as multiferroics, 4 since many of these types of compounds present some kind of magnetic ordering. In particular, porous MOFs are increasingly being studied for potential storage of different kinds of molecules. 5 Structures and, therefore, the properties of these materials may be controlled by choosing appropriate bridging ligands and metal ions.Among this kind of ligands, one of the less studied groups is that where the extreme pyridine rings are connected through sulfur atoms. In particular, the di(4-pyridyl)disulfide (DPDS) ligand 6 has an intermediate rigidity associated with the S−S bond, allowing a characteristic twisted shape and giving rise, in combination with the geometry of the metal ion, to a structural diversity of coordination polymers. This ligand also possesses two enantiomer forms (M and P) and even has potential biological applications in their broken conformations. 7 Furthermore, the DPDS ligand is known to transform in the DPS (di(4-pyridyl)sulfide) one and ot...
