Syntheses, structural diversity and photocatalytic properties of various Co(ii) coordination polymers based on a “V”-shaped 1,3-di(4′-carboxyl-phenyl)benzene acid and different imidazole bridging ligands

Abstract

Four novel Co(II) coordination polymers (CPs) based on a “V”-shaped 1,3-di(4′-carboxyl-phenyl)benzene acid (H₂dpb), namely {[Co₂(dpb)₂(4,4′-bibp)₂]·2(CH₃CN)}_n (1), [Co(Hdpb)₂(4,4′-bibp)]_n (2), {[Co₂(dpb)₂(tib)₂]·H₂O}_n (3) and {[Co(dpb)(bimb)_0.5]·DMF·0.5(CH₃CN)}_n (4) (4,4′-bibp = 4,4′-bis(imidazol-1-yl)biphenyl, tib = 1,3,5-tris(1-imidazolyl)benzene and bimb = 1,4-bis(imidazol-1-ylmethyl)benzene), have been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric (TG) analysis and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analysis reveals that complex 1 possesses a uninodal 4-connected 3D (three-dimensional) cds topology framework with the Schläfli symbol (6⁵·8). Complex 2 shows 1D zigzag chains, which are further assembled into a 3D supramolecular structure by O–H⋯O hydrogen bonds. Complex 3 shows an unprecedented 3-nodal (3,4,6)-connected 3D framework with the Schläfli symbol (6²·7)²(6⁴·7⁵·8⁴·9·10)(6⁴·8²), while complex 4 displays a {Co₂(COO)₄} binuclear SBU-based 3D 6-connected (4⁴·6¹¹)-unprecedented framework. Moreover, the photocatalytic degradation of the four Co(II) compounds (complexes 1–4) has been investigated.