Template-directed Synthesis Of A Series Of Coordination Polymers Using Metal Complexes As Templates

Coordination polymers (CPs), are assembled by the central metal ions and organic ligands or ions, to form crystalline materials with periodic and highly regular network by the intermolecular forces including coordination bonds, Van der Wals forces, hydrogen bonds,π-π stacking. CPs are series of compounds with abundant topologies as well as size-controllable channel systems, unique optical, electrical and magnetic properties. And they have attracted much more attention owing to their potential applications in storage and separation, catalysis, sensing, and fluorescent properties. More attention has been paid to the design and synthesis of new coordination polymers with interesting structures and characteristic phy-chemical properties. As one effective practice strategy, template-directed method has been more and more popular in synthesizing new CPs with intriguing structural architectures. And transition metal compounds have been widely researched in some series of inorganic materials for its large number of positive charge, adjustable molecular size and structural diversities. Our group has been committed to the synthesis of CPs by using the transition metal complexes as templates, and a series of metal-oxalate compounds with open frameworks or zeolite topologies networks have been successfully constructed.In this paper, we continued to study the synthesis of novel CPs by employing cobalt amine complexes as templates under hydrothermal/solventthermal conditions. Then the structures were analyzed and summarized, which can offer some theoretical evidence for directional synthesis of CPs with specific pore sizes, channels and topologies. Specific research results are as follows:1:A novel cadmium-oxalate compound,[Co(NH3)6]2[Cd8(C2O4)11(H2O)4]·8H2O (HNU-1), has been synthesized under hydrothermal condition in the presence of [Co(NH3)6]Cl3. Structure analysis shows that HNU-1contains12-ring channels in multiple directions. The [Co(NH3)6]3+cations and unusual hydrogen-bonded (H2O)4clusters are found in the12-ring channels with an alternative arrangement. It is believed that the (H2O)4clusters play a co-templating role in the crystallization of HNU-1. What’s more, we further summarized and analysized the relationship between the sizes of templates and the channel of the coordination polymers.2:Three novel coordination polymers,[Co(en)3]2[Zr2(C2O4)7]·4H2O (HNU-2),[Co(NH3)6][Ce(C2O4)3(H2O)]·H2O (HNU-3),[Co(dien)2][Gd(C2O4)3]·0.75H2O (HNU-4), have been hydrothermal synthesized by using [Co(en)3]Cl3、[Co(NH3)6]Cl3and [Co(dien)2]Cl3as templates, respectively. The metals (Zr4+, Ce3+and Gd3+) in the three compounds are all coordinated with four oxalates in similar with the In3+in the NKB-1possessing zeolite GIS topology network, and they can be regarded as four-connected building units, to form a OD dimer and two1D "zigzag" chains, respectively. HNU-2～HNU-4can be used as potential MBBs to construct high-dimensional structures with zeolite topologies.3:Two compounds,{[Co(en)3](H3O)2}[Cd(BTC)2Cl](HNU-5) and [Co(NH3)6][Cd2(BTC)2Cl]·3H2O (HNU-6), were synthesized under hydrothermal conditions by using [Co(en)3]Cl3and [Co(NH3)6]Cl3as templates, respectively. Structure analysis shows that HNU-5is a1D "zigzag" chain, while HNU-6is a3D open-framework structure, though they were synthesized under the same condition except the different templates. The coordination modes of the benzenetricarboxylic acids and Cl atoms are different in the two compounds, and it leads to the structures transformed from1D to3D. This may be due to the smaller size and the more hydrogen atoms to form stronger hydrogen bondings with the host framework of [Co(NH3)6]Cl3, when compared to [Co(en)3]Cl3, and this make the3D framework more stable.