Hydrothermal synthesis, crystal structure and properties of three-dimensional Co(ii)-4f heterometallic-organic frameworksElectronic supplementary information (ESI) available. CCDC 888136 (1), 888133 (2), 888134 (3), 888137 (4), 888131 (5), 888135 (6) and 888132 (7). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2ce26082d

Seven novel heterometallic-organic frameworks [Ln 2 Co(HBidc) 2 (SO 4 ) 2 (H 2 O) 8 ] n (Ln = Pr ( 1 ), Eu ( 2 ), Gd ( 3 ), Tb ( 4 ), Dy ( 5 ), Ho ( 6 ), Er ( 7 ), H 3 Bidc = 1 H -benzimidazole-5,6-dicarboxylic acid) have been synthesized under hydrothermal conditions and were characterized by elemental analysis, FT-IR, TGA analysis, powder X-ray diffraction and single crystal X-ray diffraction. Complexes 1-7 display a similar 3D (4,4)-connected 4 2 ·8 4 ( PtS ) framework. Moreover, the photoluminescence of 2 , 4 and 5 and magnetism of 3-5 have also been investigated. Seven heterometallic-organic frameworks have been constructed using H 3 Bidc with a Co(II) salt and rare earth oxide. Complexes 2 , 4 and 5 displayed lanthanide-centered luminescence and 5 may be a single molecular magnet.