Three novel and various isopolymolybdate-based hybrids built from the carboxyl oxygen atoms of in situ ligands: substituent-tuned assembly, architectures and properties.

By changing the N-donor groups of benzonitrile-based reactants, three novel isopolymolybdate-based compounds, [Cu(DBIBA)3][δ-HMo8O26] (1), [Cu(H2O)(DIBA)(DIBAH)(γ-HMo8O26)]·2H2O (2), and [CuI(DTBA)(Mo2O6)] (3) (HDBIBA = 3,5-di(benzoimidazol-1-yl)benzoic acid, HDIBA = 3,5-di(1H-imidazol-1-yl)benzoic acid and HDTBA = 3,5-di(1,2,4-triazol-1-yl)benzoic acid) were synthesized, in which the benzene carboxylate-based ligands DBIBA, DIBA and DTBA were in situ transformed from the benzonitrile-based ligands under hydrothermal conditions. Selecting benzoimidazol as the N-donor group, compound 1 with a 3D (6, 8)-connected framework is constructed from {Cu3(DBIBA)3} hexagonal ring building units and [δ-Mo8O26]4- polyoxoanions. Replacing the benzoimidazol with the imidazol group, a 3D (3, 4, 6)-connected framework 2 containing two types of {(γ-Mo8O26)(DIBA)2} building blocks was obtained. When the triazol groups are introduced, compound 3 displays a 3D framework, which is constructed from {(Mo4O13)(DTBA)2}n chains bridged by CuI atoms. It is interesting to note that the carboxyl oxygen atoms from the in situ ligands participate in the construction of isopolymolybdates in compounds 2 and 3. In addition, the various N-donor groups of in situ ligands show a great effect on the oxidation state of copper ions, the novel polymolybdate unit and the final architectures of the title compounds. The electrochemical properties and photocatalytic activities of compounds 1-3 were investigated herein.