Single-Crystal to Single-Crystal Structural Transformations of Amino-Acid-Based Coordination Polymers: Syntheses and Structural Characterization

A discrete complex [Zn(tpro)2(H2O)2] (1, Htpro = L-thioproline), and two structural isomers of coordination polymers, a 1D chain of [Zn(tpro)2]n (2) and a layer structure of [Zn(tpro)2]n (3), have been synthesized and characterized. The discrete complex 1 undergoes a single-crystal to single-crystal temperature-driven structural transformation, leading to a 1D helical coordination polymer 2. Compound 3 has a 2D homochiral layer network with a (4,4) topology. These layers are mutually linked through hydrogen bonding interactions, resulting in the formation of a 3D network. When 1 was heated, it undergoes almost completely conversion to the microcrystalline of compound 2, which was confirmed by powder X-ray diffractions (PXRD). After removing the coordinated water molecules by heating at temperature of up to 150 C, the carboxylate motifs could be activated and their orientations became distorted, after which, they attacked the activation sites of the Zn(II) centers, leading to a the formation of a 1D helix. Moreover, a portion of the PXRD pattern of 3 was converted into a pattern for 2, and the ratio between 2 and 3 was precisely determined by the simulating study of the synchrotron in situ PXRD patterns. Consequently, such a 0D complex is capable of underdoing single-crystal to single-crystal transformations and can be converted into 1D and/or 2D amino acid-based coordination polymers. Prime Archives in Polymer Technology www.videleaf.com