A 2D (4,4) network based on tetranuclear manganese(II)-terephthalato building units: Synthesis, crystal structure and magnetic studies C.P. Raptopoulou ⇑ , Y. Sanakis, K.N. Lazarou, A.N. Georgopoulou, M. Pissas, V. Psycharis Institute of Advanced Materials Physicochemical Processes Nanotechnology and Microsystems, NCSR ‘‘Demokritos’’, 15310 Aghia Paraskevi, Athens, Greece article info Article history: Received 16 September 2014 Accepted 16 October 2014 Available online 24 October 2014 Keywords: Coordination polymers Crystal structure Manganese(II) complexes Magnetic properties Terephthalato ligands abstract A two-dimensional network [Mn 4 (O 2 C-C 6 H 4 -CO 2 ) 4 (dmf) 4 (H 2 O) 2 ] n 2n(dmf) (12n(dmf)) is reported. The repeating units in 1 consist of linear tetranuclear subunits [Mn 4 (O 2 C-C 6 H 4 -CO 2 ) 4 (dmf) 4 (H 2 O) 2 ] linked through the carboxylato groups of the terephthalato ligands. The layers of 1 extend parallel to the bc crys- tallographic plane and are further associated to 3D supramolecular network through hydrogen bonding interactions. Magnetic susceptibility studies from powdered samples of 1 revealed very weak exchange coupling between the Mn II ions within the tetranuclear repeating unit. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The term coordination polymers (CPs) is used to describe a large and continuously growing class of polymeric compounds derived from metal ions or metal clusters linked via organic and sometimes inorganic ligands which extend into one, two or three-dimensions. CPs have attracted much interest in the last two decades partly due to their aesthetic and often unusual network architectures and partly due to their unique physicochemical properties which ren- der them promising for potential applications, such as gas storage, gas/vapor separation, size-, shape-, and enantio-selective catalysis, molecule-based magnetic materials, luminescent and fluorescent materials, semiconductors, and drug storage and delivery [1]. In particular, CPs based on metal carboxylate clusters as sec- ondary building units (SBUs) and organic links have led to 3D por- ous structures, i.e. metal–organic frameworks (MOFs), whose pore size and functionality can be varied systematically due to the spe- cific structural characteristics of the SBUs where each metal ion is locked into certain position by the carboxylates. In a variety of cases, metal carboxylates behave as simultaneously SBUs and organic linkers, i.e. cases where carboxylates contain more than one –COO  entities which can either fulfill the coordination requirements of the metal ions in one SBU and also connect the SBUs together in one-, two- and three-dimensions. Within that respect, the terephthalate dianion,  O 2 C-C 6 H 4 -CO 2  , has been widely used as an effective bridging ligand between metal ions tak- ing advantage of the coordination versatility of its two carboxylato moieties and its rigid skeleton. For example, [Mn 3 (O 2 C-C 6 H 4 - CO 2 ) 3 (def) 2 ] n , MOF-73 [2] (def = diethyl formamide), consists of tri- nuclear SBUs formed through two l-syn,syn, two l 2 -j 2 O: jO 0 and two l 2 -j 2 O: j 2 O 0 –COO  moieties; the latter also link the [Mn 3 ] SBUs into one direction, thus forming Mn–O–C rods. The benzene units of the terephthalato ligands connect each rod to four neigh- boring rods, resulting in a pcu arrangement with rhombic channels into which the def molecules reside as coordinated guests. Replacement of the bigger def molecules with the smaller dmf molecules resulted in an analogous structure, [Mn 3 (O 2 C-C 6 H 4 - CO 2 ) 3 (dmf) 2 ] n [3], with rhombic channels of comparable dimen- sions. Analogous reactions have afforded 3D porous materials based on dinuclear, [Mn 2 (O 2 C-C 6 H 4 -CO 2 ) 2 (dmf) 2 ] n [4], or mononu- clear [Mn(O 2 C-C 6 H 4 -CO 2 )(H 2 O) 2 ] n SBUs [5], as well as 2D networks with 3 6 topology, [Mn 3 (O 2 C-C 6 H 4 -CO 2 ) 3 (dma) 4 ] n (dma = dimethyl- acetamide) [6], [Mn 3 (O 2 C-C 6 H 4 -CO 2 ) 3 (dmf) 4 ] n [7], and [Mn 3 (- atpa) 3 (dmf) 4 ] n (atpa = 2-aminoterephthalic acid) [8]. In an attempt to construct metal-carboxylate networks with unprece- dented topologies and network architectures, other multidentate ligands have been simultaneously used, thus leading to mixed ligand manganese-terephthalato 1D, 2D and 3D networks [9]. With these considerations in mind we have embarked into a research program targeting the development of CPs of various dimensionalities and network topologies, based on manganese- terephthalato SBUs in the presence and/or absence of other multid- entate ligands. We present herein, the synthesis, crystallographic and magnetic study of [Mn 4 (O 2 C-C 6 H 4 -CO 2 ) 4 (dmf) 4 (H 2 O) 2 ] n- 2n(dmf) (12n(dmf)) which presents two-dimensional structure. http://dx.doi.org/10.1016/j.poly.2014.10.011 0277-5387/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +30 210 6503346; fax: +30 210 6519430. E-mail address: craptop@ims.demokritos.gr (C.P. Raptopoulou). Polyhedron 85 (2015) 783–788 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly