pH, solvent and metal ion induced octamolybdate-based metal–organic complexes decorated with a pyridyl-carboxylate ligand containing an amide group†
Abstract
Three octamolybdate-based metal–organic complexes constructed from a pyridyl-carboxylate ligand containing an amide group, 3-(2-pyridinecarboxylic acid)amido pyridine (HPCAP), namely, H2{[Cu3(PCAP)4(H2O)2](β-Mo8O26)}·10H2O (1), H{[Cu(PCAP)(H2O)](β-Mo8O26)0.5} (2) and H2[Co(H2O)6][Co2(PCAP)4(γ-Mo8O26)(H2O)2]·10H2O (3), have been successfully synthesized under hydrothermal or solvothermal (methanol–water mixed solvent) conditions. Single-crystal X-ray analyses reveal that compound 1 is a 2D layer based on infinite 1D [Cu3(PCAP)4]n2n+ chains and bidentate β-Mo8O264− anions. In compound 2, 1D “thin centipede” [Cu2(PCAP)2]n2n+ chains were connected by tetradentate β-Mo8O264− anions through the Cu–O bond to form a 2D network. In compound 3, γ-Mo8O264− anions were connected by adjacent [Co2(PCAP)4(H2O)2] moieties through Co–O and Mo–N bonds forming an uncommon 1D “fat centipede” chain. The adjacent chains were further extended to a 2D supramolecular network through hydrogen bonding interactions. The title compounds represent the first examples of introducing a pyridyl-carboxylate ligand containing an amide group into the POM system. The pH value, solvent and metal ions play key roles in the construction of the final architectures and show a great influence on the structural diversities of the title compounds. The electrochemical properties of compound 1 and the photocatalysis properties of the title compounds have been reported.