Crystal Structures And Luminescence Of Complexes Of Bis-[(3,5-dimethyl)-4-pyrazole]methane: Toward The Effect Of Second Ligands

Spaced-bipyrazole ligands are a family of polydentate, middle-hard-base donors that can form stable coordination compounds with most of transition metal ions. Because of their labile, non-chelating and linking coordination modes, the ligands can be used as linkage for construction of structurally intriguing coordination polymers, thus they have attracted extensive attention of current coordination chemistry. For that reason, we prepared a ligand, namely, bis-[(3,5-dimethyl)-4-pyrazole]methane (DMPM) and, using it as primary ligand, along with different second ligand, synthesized 11 coordination polymers, which were structurally identified by single crystal and powder X-ray diffractions, and some of which were photophysically investigated. Herein, we report the structures and properties of these products sorted according to the types of second ligands.Chapter 1 introduces briefly the progress of coordination chemistry research and the factors affecting the construction of complexes. Subsequently a survey on the on-going advance of DMPM coordination chemistry is made and finally the aim of the present work is elucidated.In chapter 2, we reports three new complexes, synthesized from reactions of DMPM, as main ligand, and linking anions (I-, SCN-,SO42-), as second ligands, with metal salts. Among the products, [Cd(I)2(DMPM)] (1) is a zero-dimensional (0-D) dinuclear complex, while [Cd(SCN)2(DMPM)2]n (2) and [Cu(SO4)(DMPM)]n (3) are 1-D. In all three compounds, the first ligands act as angular linkers. In crystal packing, all three compounds give the high-dimensional supramolecular systems unified via hydrogen bonds.Chapter 3 includes four Cd2+ complexes with DMPM as primary ligand and aromatic polycarboxylic acids (phthalic (H2PA), terephthalic (H2TPA), isophthalic (H2IPA), and benzene-1,3,5-tricarboxylic (H3BTA)) as axiliary ligands. X-Ray structural analysis reveals that [Cd(BA)(Cl)(DMPM)2]n (4) is uniquely assembled in 1-D because the H2PA losses one of two carboxylates and so acts as a terminal ligand, stopping the extension of coordination polymer along its propagation. For the reason, the complex, in virtue of the linking of DMPM, structures as a chain running along a direction. Complexes, [Cd(TPA)(DMPM)]n(5), [Cd(IPA)(DMPM)]n(6), [Cd(HBTA)(DMPM)]n(7), are 2-D. Particularly, the first ligands in 5 are cis-configured, incorporating into TPAs, give a plain three-connection (6,3) topology. Instead, those in 6 are configured as either cis or trans, of which the cis, combining to Cd2+ ions, furnishes the zigzag chains and the trans, combining to Cd2+ ions, furnishes the helices. With incorporation of Cd2+ into the diversely configured DMPMs and angular IPAs, the ternary polymer gives a binodal (52.62.72)(53.63) topologized net. Indicatively, the first ligands in 7 are all trans-configured, to work together with HBTA, rendering a (4, 4) network. Luminescence spectra of three 2-D complexes suggest that the energies of DMPM-based emissions of them are analogous, but not the widths. A suggestion of the observation is that the photoresponse of DMPM is subject to its coordination manner. What is more, the thermal analysis reveals that the complexes are decomposed in the same way, but different in the desertion temperature of DMPM, based on which we can conclude that the second ligands affect not only the coordination mode of DMPM and assembly of coordination polymers, but also their luminosity and thermal property.In chapter 4, four complexes with DMPM as first ligand and pyridine dicarboxylic acids (2,5-pyridine dicarboxylic acid (2,5-PDC), 2,6- pyridine dicarboxylic acid (2,6-PDC)) as second ligands, are demonstrated, of which the [Cd(3-PDC)2(DMPM)]n (8) is 2-D and can be reduced into a (44, 62) topological network, therein the 2,5-PDC appears as 3-picolinic acid for the decarboxylation of 2-position and gives the double-stranded helix, in combination to Cd2+. Instead, the [Zn(2,5-PDC)(DMPM)]n (9) constructs as a 1-D triple strand. In another comparison, the Cl-involving [Cd2(2,6-PDC)(μ2-Cl)(Cl)(DMPM)·H2O]n (10) configures as a 2-D network presenting a (42.62)2(42.62.82) topology, in contrast to the I-involving [Cd2(2,6-PDC)I2(DMPM)]n (11), as a grid-like network. Fluorescence of 8 and 10 indicates that the photoresponses of two compounds are comparable, meaning that the position-isomeric second ligands not significantly affect the bulk photobehavior of the complexes.