In the thesis, synthetic approaches directed towards coordination polymers based on bridging multifunctional 1,2,4-triazole ligands were explored. The syntheses of the complexes have been developed and elaborated, and their structural features have been established as well. The obtained compounds comprise the prototypes of organo-inorganic materials with a wide range of functional properties, from magnetism and luminescence to sorption and catalysis. These compounds were identified and characterized by modern physical methods, including single-crystal X-Ray analysis, powder X-Ray diffraction and temperature-dependent powder X-ray measurements, DTA-TG-MS, IR spectroscopy, 1H NMR, CHN, mass spectrometric measurements in solutions, energy dispersion X-ray scattering, electron and luminescent spectroscopy, scanning electron microscopy, temperature-dependent magnetic susceptibility, sorption and catalytic studies. The crystal structures of 132 new coordination compounds were confirmed by single-crystal X-ray analysis. Quantitative parameters of interatomic bonds and angles, types of polymer topologies, intermolecular (supramolecular) interactions, such as hydrogen, π-π stacking and anion-π, etc. were determined using X-ray crystallography. A clear relationship between the chemical composition and structure of compounds, on the one hand, and functional properties, on the other hand, has been established.
Simplest bistriazole ligand (btr) was employed to demonstrate the possibilities for the integration of polynuclear ensembles into extended arrays, in which the triangular [Cu3(μ3-OH)(tr)3]/[Cu3(μ3-O)(tr)3] or linear clusters [Cu3(μ2-Cl)2Cl2(tr)4] (or [Cu3(μ2-OH)2(tr)4]) are applicable as secondary building units. In these compounds the organic ligand tends to increase its connectivity (μ3 and μ4) and short inorganic bridges (OH-, O2- and Cl-) display an important supporting role in the overall architectures.
The coordination-chemical behavior of heterobifunctional Hpztr towards CuII salts significantly depends on reaction conditions employed. Two synthetic protocols demonstrate the principal ways that can selectively involve the coordination of either triazole or pyrazole groups (the latter appears in the pyrazolate anionic form). In particular, the interaction in hot aqueous solutions leads to the crystallization of one-dimensional coordination polymers [CuII(μ2-OH)]n stabilized by triazole bridges. The bridging role of pyrazole is more preferable in CH2Cl2 medium when CuCl2•2H2O (or CuBr2) reacts with Hpztr and a strong base (solid NaOH) in the presence of lipophilic organic cations as interphase carriers. This interaction affords crystallization of the cyclic hexanuclear hydroxypyrazolate species ([CuІІ6(μ2-OH)6(pztr)6]). The crystal structure shows that the complexes belong to the particles of anionic nature that is a result of encapsulation of one halide anion (Cl- or Br-) inside the inner cavity. These complexes are representative examples of supramolecular-container molecules, which external shape reminds a double bowl. This structure promotes the selective inclusion of a number of guest molecules.
The simultaneous binding of metal ions to bistriazole and polycarboxylate ligands opens the way to generate the thermally stable coordination frameworks of neutral types, which built up from low-nuclear coordination clusters. Alternatevely, 1,2,4-triazolecarboxylic acids, derived from alpha-aminocarboxylic acids, have shown significant potential as building blocks for the synthesis of CuII and AgI coordination frameworks, in which triazole and carboxylate bridges are synergistically combined.
It was shown that the concept of composition space diagrams represents a significant advantage for the multicomponent systems containing CuII, triazole ligand and MoVI-oxide precursor. This methodological approach contributes to a better understanding of how the crystal structure form in the mixed-metal coordination polymers, it also allows to determine the crystallization fields of the compounds formed and to optimize the methods of their synthesis. The mixed-metal triazole-containing CuII-molybdates demonstrated high efficiency as heterogeneous catalysts in the oxidation of benzyl alcohol.
The coordination-chemical behavior of 1,2,4-triazoles in hydrothermal reactions with MoO3 was studied in details. It demonstrated prospects for the supramolecular synthesis of metalloxide–organic frameworks. A key structure of the hybrids is the [N-N]-bridging function of the triazole group that supports the polymeric inorganic subtopologies [–O-Mo(O)2-]n. The metal-oxide coordination polymers proved to be effective catalysts for a wide range of reactions (epoxidation of olefins, oxidative dehydrogenation of alcohols, etc.) that occured with the participation of organic and inorganic peroxides. It was found that the [MoO3(tradcH)]•H2O coordination polymer behaves as a reaction-induced self-separating catalyst.
