Metal-directed 1-D molecular-box based coordination polymers with mono- and di-nuclear nodes – Construction of 3-D supramolecular networks via hydrogen bonding and S⋯S interactions

Self-assemblies of 4-pyridylthioacetic acid (Hpyta) with CdCl2 or HgCl2 yield the polymeric metal-organic coordination frameworks [Cd(pyta)2(H2O)]n (1) and [Hg(pyta)Cl]n (2). X-ray single-crystal diffraction results reveal that both complexes display similar 1-D neutral coordination arrays containing approximate rectangular molecular box subunits, which are, however, linked via mononuclear CdII and dinuclear Hg2O2 nodes. For 1, the adjacent 1-D motifs are interconnected to form a 2-D layer via O–H⋯O hydrogen bonds and further engender a 3-D network by weak S⋯S interactions; whereas complex 2 possesses a novel 3-D supramolecular architecture with the aid of abundant C–H⋯Cl and S⋯S contacts. Interestingly, due to the intrinsic difference of the metal ions, the carboxylate group of the pyta ligand displays symmetric bidentate chelate mode for 1 and monoatomic bridging fashion for 2; the latter case is unprecedented in coordination chemistry of pyta. These results clearly suggest that it is an effective synthetic strategy by employing coordinative forces and concomitant noncovalent contacts to construct the fine-tuning supramolecular networks.

Graphical abstractTwo 1-D molecular-box based coordination polymers [Cd(pyta)2(H2O)]n (1) and [Hg(pyta)Cl]n (2) with different mono- and di-nuclear nodes directed by the metal ion selection, are achieved by assembly of metal chloride with a versatile flexible molecule 4-pyridylthioacetic acid (Hpyta). The 3-D supramolecular architectures for both complexes with the aid of hydrogen-bonding and weak S⋯S interactions are further analyzed, suggesting that such noncovalent contacts are also important elements in tuning the network structures. The binding features of pyta in all known complexes have been discussed in detail.Figure optionsDownload full-size imageDownload as PowerPoint slide