Construction of Alkali-metal-based Imidazolecarboxylate Coordination Polymers as Efficient Catalysts for Solventfree Ring-opening polymerization of ɛ-Caprolactone.

A series of new alkali-metal-based coordination polymers, [Li(H2IMDC)(H2O)]n (1), [Na2(H2IMDC)2(H3IMDC)2(H2O)4]n (2), and [K(H2IMDC)(H2O)]n (3), have been constructed under solvothermal conditions by using imidazole-4,5-dicarboxylic acid (H3IMDC) as ligand. The structure of the complexes has been determined by single-crystal X-ray diffraction and further characterized by elemental analyses, IR spectra, powder X-ray diffraction and thermogravimetric analyses. The single crystal Xray structural studies showed that their structural dimensionalities varying from 1-D zigzag chain, 2-D 44-sql network to 3-D 4,6-connected coordination framework are strongly governed by the ionic radii and coordination geometries of the metal cations. For the first time, the alkali-metal-based coordination polymers were demonstrated to be effective catalysts for the solvent-free ring-opening polymerization (ROP) of ɛ-caprolactone. The catalytic activity of complexes 1–3 depends on the metal cations, increasing in the order Li+ < Na+ < K+. [ABSTRACT FROM AUTHOR]