Synthesis, structure, novel topology and reversible crystal-to-amorphous transformation of calcium coordination polymers from a flexible tripodal acid with additional amide groups

Two novel coordination polymers, [Ca(HTCMBT)(H2O)2]n (1) and {[Ca6(TCMBT)4(H2O)14]·(H2O)3}n (2), have been successfully synthesized from a tripodal flexible ligand, N,N′,N″-tris(carboxymethyl)-1,3,5-benzenetricarboxamide (H3TCMBT). Single crystal X-ray diffraction analyses reveal that 1 possesses a 2D network, in which each double layer is composed of dinuclear calcium clusters and OSBUs, and such layers further stack through hydrogen bonds to form a 3D supramolecular framework, while 2 exhibits a 3D architecture comprising mononuclear and dinuclear calcium units and OSBUs, which is a quite rare (5,6,8)-connected net with an unprecedented {3.46.52.6}2{32.44.54.64.7}{32.48.57.69.72} topology. In addition, 2 displays an interesting reversible crystal-to-amorphous transformation.

Graphical abstractOne of two novel calcium(II) complexes from a flexible tripodal acid with amide groups exhibits a rare (5,6,8)-connected net with an unprecedented {3.46.52.6}2{32.44.54.64.7}{32.48.57.69.72} topology and an interesting reversible crystal-to-amorphous transformation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two calcium coordination polymers have been synthesized from a tripodal flexible ligand. ► Complex 1 and 2 possess 2D and 3D networks, respectively. ► They all have organic secondary building units with each constructed by two ligands. ► Complex 2 exhibits an unprecedented topology and reversible crystal-to-amorphous transformation.