Synthesis, structural diversity, and thermal decomposition kinetics of four interpenetrating Zn(II)/Cd(II)/Ni(II) coordination polymers

Four interpenetrating coordination polymers, namely, [Zn(bib)(0.5)(2,6-ndc)](n) (1), {[Cd(bib)(2,6-ndc)]center dot 2H(2)O}(n) (2), [Cd-2(bib)(2)(1,4-ndc)(2)]center dot H2O}(n) (3), [Ni-2(bib)(1.5)(1,4-ndc)(2)(H2O)](n )(4), (bib = 1,4-bis(2-methyl-imidazol-1-yl) butane, 1,4-H(2)ndc = Naphthalene-1,4-dicarboxylic acid, 2,6-H(2)ndc = Naphthalene-2,6-dicarboxylic acid) have been synthesized under solvothermal conditions. Their structures were characterized by elemental analysis, IR spectra, single-crystal and powder X-ray diffractions. Structural analyses reveal that compound 1 exhibits a 3-fold interpenetrating 3D net with pcu topology. Compound 2 presents a 5-fold interpenetrating 3D dia framework. Compound 3 displays an unusual [2 + 2] 4-fold interpenetrating 3D dia framework. Compound 4 features a 2-fold interpenetrating 3D framework. Simultaneous TG-DSC techniques were applied to assess the thermal decomposition behavior of compounds 1-4. TG measurements indicate that compounds show higher stability as the interpenetrating number increase. The thermal analysis kinetic parameters (apparent activation energy E and the pre-exponential factor A) of skeleton collapse for the compounds 1-4 were calculated by the methods of Kissinger and Ozawa-Doyle. The thermodynamic parameters (Delta H-not equal, Delta G(not equal), and Delta S-not equal) at peak temperatures were also calculated.