Four new metal–organic frameworks based on a rigid linear ligand: synthesis, optical properties and structural investigation

Abstract

Four coordination polymers, namely, {[Cd(L)(BIP)]·3H₂O}_n (1), {[Co(L)(BIBP)(H₂O)₄]·4H₂O}_n (2), {[Ni(L)(BIBP)(H₂O)₂]·2DMF}_n (3), [Ni(L)(BIMB)(DMF)(H₂O)]_n (4), have been synthesized based on a rigid linear carboxylate ligand (H₂L = 2′,5′-dimethoxy-[1,1′:4′,1′′-terphenyl]-4,4′′-dicarboxylic acid) and different lengths of imidazole ligands (BIP = 1,4-di(1H-imidazol-1-yl)benzene; BIBP = 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl; BIMB = 4,4′-bis((1H-imidazol-1-yl)methyl)-1,1′-biphenyl). These complexes have been characterized by single crystal X-ray diffraction, infrared spectroscopy, thermogravimetry, elemental analysis, and powder X-ray diffraction measurements. Complex 1 is a 6-connected 3-fold interpenetrating pcu net with the point symbol {4¹²·6³}, 2 is a 1D supramolecular chain-like structure, 3 and 4 can be simplified as 4-connected sql nets with the point symbol {4⁴·6²}. In addition, UV-visible spectra and photoluminescent properties are also investigated in detail.