A series of POM-based entangled frameworks with the rigid ligand 1,4-bis(1-imidazolyl)benzene and different isomers of octamolybdate

With BIMB ligand, we have successfully obtained and characterized three novel entangled inorganic–organic hybrid compounds by choosing different metal ions, that is, [Ni(BIMB)2(γ-Mo8O26)0.5]·3H2O (1), [Zn(BIMB)2(γ-Mo8O26)0.5] (2), and [Cu3(BIMB)4(H2O)(δ-Mo8O26)Cl2]·3H2O (3) (where BIMB=1,4-bis(1-imidazolyl)benzene). Compound 1 is a 2-fold interpenetration 4-connected 3D framework with the short Schläfli symbol of (4×64×8)2(42×62×82), in which octamolybdate anion shows γ-isomer; 2 exhibits a (5,6)-connected 3D self-penetrating topological motif with the short Schläfli symbol of (4×57×62)2(42×511×72), and 3 shows a (4,6)-connected self-penetrating 3D framework with the short Schläfli symbol of (42·52·6·7) (44·5·69·8) (54·62) whose octamolybdate has δ-isomer. In addition, the optical band gaps of these three compounds have been measured, which are 2.98 eV for 1, 3.42 eV for 2, and 2.88 eV for 3. Moreover, 2 has photoluminescent property, which can be attributed to ligand-to-metal charge-transfer (LMCT) band.

Graphical abstractWith BIMB ligand, we have obtained and characterized three novel POM-based entangled hybrid compounds. Compound 1 is a 2-fold interpenetration 3D framework; 2 and 3 exhibit self-penetrating 3D polycatenated frameworks.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Three novel octamolybdate-based entanglement frameworks successfully obtained by choosing the rigid ligand 1,4-bis(1-imidazolyl)benzene and different metal ions. Compound 1 is a 2-fold interpenetration 4-connected 3D framework; 2 exhibits a (5,6)-connected 3D self-penetrating topological net, and 3 shows a (4,6)-connected self-penetrating 3D framework. ► In compounds 1 and 2, the octamolybdate anions show the γ-isomer, while in 3 the octamolybdate anion is a δ-isomer. ► Optical band gap of these three compounds have been investigated and the results show that they are all wide gap semiconductors, which are 2.98 eV for 1, 3.42 eV for 2, and 2.88 eV for 3.