Six New Metal-Organic Frameworks Based on Polycarboxylate Acids and V-shaped Imidazole-Based Synthon: Syntheses, Crystal Structures, and Properties

Solvothermal reactions of 4,4'-bis(imidazol-1-yl)diphenyl ether (BIDPE) with deprotonated 5-hydroxy-isophthalic acid (5-OH-H(2)bdc), and benzene-1,3,5-tricarboxylic acid (H(3)btc) in the presence of cadmium(II), zinc(II), cobalt(II), nickel(II), and manganese(II) salts in H2O or H2O/DMF produced six new complexes, namely, [Cd(BIDPE)(5-OH-bdc)center dot H2O](n) (1), [Co(BIDPE)(5-OH-bdc)center dot H2O](n) (2), [Zn-3(BIDPE)(3) (5-OH-bdC)(3)center dot 4H(2)O](n) (3), [Ni(BIDPE)(2)(5-OH-bdc)(H2O)center dot 3H(2)O](n) (4), {[Mn-2(BIDPE)(2)(5-OH-bdc)(2)](n), (5), and [Ni(BIppE)(2)(Hbtc)(H2O)](n) (6). These complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Compounds 1 and 2 reveal the same two-dimensional (2D) sheets with a 32-membered [(Cd/Co)(2)(BIDPE)(2)] metallocyclic ring constructed from BIDPE and 5-OH-H(2)bdc with Cd or Co salts. For compound 3, six identical 2D sheets are polycatenated in parallel to form a rare 2D 2D framework; it displays ferroelectric behavior with a remnant electric polarization (P-r) of 0.033,mu C/cm(2) and an electric coercive field (E-c) of 11.15 kV/cm. In compounds 4 and 6, only one carboxyl group coordinated to the Ni atom from 5-OH-H(2)bdc or H(3)btc. Compound S exists as binuclear Mn clusters, which are linked by BIDPE and 5-OH-H(2)bdc to generate a 2D sheet and displays weak antiferromagnetic character. In addition, the thermal stabilities and photochemical properties of these new complexes have been studied.