Substituted groups-directed assembly of Cd(ii) coordination polymers based on 5-R-1,3-benzenedicarboxylate and 4,4'-bis(1-imidazolyl)bibenzene: syntheses, structures and photoluminescent properties

Hydrothermal reactions of CdCl2·2.5H2O with 4,4'-bis(1-imidazolyl)bibenzene (bimb) and 1,3-benzenedicarboxylate (1,3-H2BDC), 5-methyl-1,3-benzenedicarboxylate (5-Me-1,3-H2BDC), 5-amino-1,3-benzenedicarboxylate (5-NH2-1,3-H2BDC), 5-hydroxy-1,3-benzenedicarboxylate (5-HO-1,3-H2BDC), 5-nitro-1,3-benzenedicarboxylate (5-NO2-H21,3-BDC), or 5-sulfo-1,3-benzenedicarboxylate (5-HSO3-1,3-H2BDC) resulted in the formation of six Cd(II) coordination polymers, [Cd(5-R-1,3-BDC)(bimb)]n (R = H (1), R = Me (2), R = NH2 (3), R = OH (4)), {[Cd2(H2O)(5-NO2-1,3-BDC)2(bimb)]·2H2O}n (5) and [Cd(5-SO3-1,3-HBDC)(bimb)]n (6). Compounds 1–6 were characterized by elemental analysis, IR, powder X-ray diffraction and single-crystal X-ray diffraction. 1–4 exhibit similar 3D frameworks in which 2D [Cd4(5-R-1,3-BDC)4]n (R = H, Me, NH2 and OH) layers are interlinked by bimb ligands. 5 has a two-fold interpenetrating 3D framework in which 1D [Cd2(5-NO2-1,3-BDC)2]n chains are interconnected by bimb ligands. 6 shows a 3D (3,5)-connected framework in which 2D [Cd2(5-SO3-1,3-HBDC)2]n networks are bridged by bimb ligands. The Schläfli symbols for these six 3D nets are (4·62)(4·66·83) (1–4), (42·6)(42·6·102·12) (5) and (4·6·8)(4·65·83·10) (6). The solid state photoluminescent properties of 1–6 were also investigated.