INORGANIC CHEMISTRY FRONTIERS RESEARCH ARTICLE Cite this: Inorg. Chem. Front., 2015, 2, 157 Received 11th November 2014, Accepted 7th December 2014 DOI: 10.1039/c4qi00201f rsc.li/frontiers-inorganic A 2-D coordination polymer incorporating cobalt(II), 2-sulfoterephthalate and the flexible bridging ligand 1,3-di(4-pyridyl)propane† Amitabha Datta,* a Kuheli Das, b Chiara Massera, c Jack K. Clegg,* d Michael C. Pfrunder, d Eugenio Garribba, e Jui-Hsien Huang,* a Chittaranjan Sinha,* b Tapas Kumar Maji, f Takashiro Akitsu g and Shingo Orita g The cobalt derivative {[Co 3 (2-stp) 2 (dpp) 4 ]·2H 2 O} n (1) has been hydro(solvo)thermally synthesised by com- bining sodium 2-sulfoterephthalic acid (2-stpH 2 Na) and divalent cobalt nitrate in presence of the flexible N-donor co-ligand dpp (1,3-di(4-pyridyl)propane). Single-crystal X-ray diffraction shows that 1 is a two- dimensional coordination polymer with carboxylate and sulfonate oxygens and pyridyl nitrogens co- ordinated to the two symmetry independent octahedral cobalt(II) centres. UV-Vis, magnetic and EPR studies show that the cobalt(II) centres are high-spin. Compound 1 proved to be robust to the removal of the solvent water molecules, which was achieved by heating the sample to yield the desolvated complex {[Co 3 (2-stp) 2 (dpp) 4 ]} n (2). 2 was also characterised by single-crystal X-ray diffraction at 331 K. Gas sorption studies on this material showed only surface binding of N 2 and modest uptake for CO 2 . The crystallo- graphic analysis also shows that upon desolvation, the flexible propyl groups of the dpp ligand adjust their positions, reducing the potentially accessible void volumes and accounting for the gas adsorption results. Introduction The preparation of coordination polymers has received signifi- cant interest due to both their diverse network topologies 1 and the wide number of potential applications in catalysis, storage, separation and sensing, along with their many interesting physical properties including unusual chirality, luminescence and magnetism. 2 While it is possible to design new coordi- nation polymers with the help of reticular methods 3 and, to some extent, predict their properties using computational methods, 4 the applicability of these methods are often limited to systems in which rigid symmetric ligands is to be employed. Accordingly, the most used building blocks in the construction of coordination properties have been the bipyridine and imida- zole-type ligands containing N donor groups, and the versatile aromatic carboxylic ligands. The incorporation of flexible brid- ging ligands into coordination polymers has received signifi- cantly less attention due to the unpredictability of the connectivity of the final assembly. 5,6 Despite this limitation, the use of flexible components has the potential to yield materials with structures and functions that are inaccessible when rigid components alone are employed. 5,7 With the aim of producing materials with either unusual topologies or physical properties, we have recently investigated the formation of new metal–organic frameworks incorporating the rigid but non-symmetrical 2-sulfoterephthalate (2-stp) ligand. 8 This ligand presents a diverse number of potential coordination and bridging modes, along with multiple accessi- ble protonation states due to the presence of both the carboxy- late and the sulfonate groups. In addition, the aromatic spacer provides π-surfaces for intermolecular interactions. When 2-stp was used in combination with the rigid linear 4,4′- bipyridine (bipy) building block both a zinc-containing † Electronic supplementary information (ESI) available: Additional details of the physical methods, additional figures and additional topological discussion, crys- tallographic data in CIF format. CCDC 936366 and 1003710. For ESI and crystal- lographic data in CIF or other electronic format see DOI: 10.1039/c4qi00201f a Department of Chemistry, National Changhua University of Education, Changhua 50058, Taiwan. E-mail: amitd_ju@yahoo.co.in, juihuang@cc.ncue.edu.tw b Department of Chemistry, Jadavpur University, Kolkata – 700032, India. E-mail: c_r_sinha@yahoo.com c Dipartimento di Chimica, Università degli Studi di Parma, Viale delle Scienze 17/A, 43124 Parma, Italy d School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane St Lucia, QLD 4072, Australia. E-mail: j.clegg@uq.edu.au e Dipartimento di Chimica e Farmacia, and Centro Interdisciplinare per lo Sviluppo della Ricerca Biotecnologica e per lo Studio della Biodiversita della Sardegna, Universitá di Sassari, Via Vienna 2, I-07100 Sassari, Italy f Molecular Materials Laboratory, Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur, Bangalore 560064, India g Department of Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan This journal is © the Partner Organisations 2015 Inorg. Chem. Front. , 2015, 2, 157–163 | 157 Published on 15 December 2014. Downloaded on 12/08/2016 01:19:01. View Article Online View Journal | View Issue