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.