Design, Synthesis And Properties Of Organic Ligands And Complexes Based On 1,4-Subsititued-1,2,3-Triazole

Design and synthesis of new coordination complexes has been attracted great attention over the past few decades due to their wide applications and excellent properties in many areas such as Organic/Polymeric Light Emitting Diodes, Dye Sensitized Solar Cells, Heterojunctional Organic/Polymeric Photovoltaics, Nonlinear Optical materials, Field-Effect Transistors, Molecular Magnets, Porous materials, Metal-Organic Frame works, Ferroelectric/Dielectric materials, Molecular Devices, Chemical Biological Sensors etc.. Recently, much attention has been focused on the design and synthesis of 1,4-substituted 1,2,3-triazoles via the copper（I） catalyzed azide-alkyne 1,3-dipolar cycloaddition （the CuAAC reaction） firstly discovered by Sharpless, Meldal and co-workers in 2002, which showed great advantages such as environmental friendly, high efficiency, high region-selectivity and much easily to perform. Therefore, triazoles obtained from CuAAC reaction have been widely used in polymer design, macromolecular engineering, bio-medicinal molecule synthesis, and surface functionalization. However, most research only applied 1,4-subsititued-1, 2,3-triazoles as a simple linkage and few works has focused on coordination of 1, 4-subsititued-1,2,3-triazole with metals. As can be seen, both N2 and N3 nitrogen atoms in 1,2,3-trizole contain unpaired electrons, so these nitrogen atoms can act as donors to coordinate to metals. In this research, we focus our works on the coordination of N2 atom with low electron density in 1,4-subsititued-1,2,3-triazoles with different metals, and wish to enhance its coordination ability through molecular design and chemical synthesis via "chelating effect" on it. Thus, a series of ligands based on 1,2,3-triazole unit and corresponding complexes have been synthesized. The single crystal structure is determined and physical properties are also studied. In addition, theoretical calculation has also been applied to explain some experimental results.The main contents of this thesis are described as following: Chapter 1 briefly introduced the structural characteristic of non-substituted 1,2, 3-triazole and the reaction mechanism of CuAAC reaction for the synthesis of 1, 4-subsititued-1,2,3-triazole. Then the most recent research progress for 1, 4-subsititued-1,2,3-triazoles used as ligands or building blocks for bio-medical complexes, super molecular self-assemblies and recognitions, coordination chemistry has been reviewed. Finally the design strategies and main contents for this thesis are outlined.In Chapter 2,2-[（4-phenyl-1H-1,2,3-triazol-1-yl） methyl] pyridine （L1） as a model ligand and 4-[（4-phenyl-1H-1,2,3-triazol-1-yl） methyl] pyridine （L2） as a reference ligand have been synthesized. A series of new Cu（Ⅱ） complexes of L1, L2 and their corresponding synthetic intermediates,2-（azidomethyl） pyridine （M1） and 4-（azidomethyl） pyridine （M2）, including Cu（M1）2Cl2 （Ⅱ1）, Cu（M1）Cl2 （Ⅱ2）, Cu（L1）2 Cl2（Ⅱ3）, Cu（M2）2 Cl2 （Ⅱ5） and Cu（L2）2Cl2 （Ⅱ6） have been synthesized. In addition, a coordination polymer CuCl2Cu（N3）2 L1（Ⅱ4） with mixed anions and a dinuclear complex （Cu2 （μ-N3）2 （N3）2 （L2）2） （Ⅱ7） have also been prepared. The crystal structure for all the complexes has been determined by single crystal diffraction. The experimental results as well as TD-DFT calculation for L1 and L2 reveal that the "Chelate effect" plays an essential role when coordination ability of N2 atom in 1,4-subsititued-1,2,3-triazoles has been enhanced, although it shows much lower electron density than N3 atom. The magnetic properties of several complexes were measured by SQUID. The magnetic behavior revealed that the intramolecular ferromagnetic interactions existed between the Cu-Cu cations in Cu（M1）Cl2, while the intramolecular anti-ferromagnetic interactions existed between the Cu-Cu cations in CuCl2Cu（N3）2L1, Cu（M2）2Cl2, Cu（L2）2Cl2, Cu2（μ-N3）2 （N3）2 （L2）2 under the experimental conditions. Among them, the Cu（M2）2Cl2 is a low-temperature anti-ferromagnet with a Neel temperature of 13 K.In Chapter 3, a series of transition metal complexes based on L1 has been synthesized and characterized. Single crystal analysis shows that Mn2（μ-Cl）2 （H2O）2Cl2 （Ⅲ1） is a 6 coordinated dinuclear Mn（Ⅱ） complex with a distorted octahedron geometry. Co（Ⅱ） and Ni（Ⅱ） metals coordinated with L1 yield mononuclear complexes including Co（L1）2Cl2 （Ⅲ2）, Ni（L1）2 Cl2 （Ⅲ3） and Ni（L1）2（N3）2 （Ⅲ4）, in which metals also are in distorted octahedron geometry with the coordination numbers of 6. However, Zn （Ⅱ） complex, Zn（L1）Cl2 （Ⅲ5） is a 4 coordinated complex which shows a twisted tetrahedron geometry. The TD-DFT calculation is applied to explain the formation of some complexes. UV-Vis absorptions of all complexes are studied, theÏ€-Ï€* transition and MLCT （Metal-to-Ligand-Charge-Transfer） absorption bands have been observed forâ…¢1-â…¢5, but the d-d transition bands only existed inâ…¢2,â…¢3 andâ…¢4. The magnetic measurement for dinuclear complexâ…¢1 indicates that it is a paramagnet with weak ferromagnetic coupling between the two Mn （Ⅱ） spins.In Chapter 4, two Ag （Ⅰ） complex containing weak coordinated anion PF6-（IV1） and SbF6- （Ⅳ2） based on L1 has been synthesized and characterized. The structure data forâ…£2 illustrates that the complex has a formula of [Ag3（L1）4] （SbF6）3. The IV2 is an unusual Ag （Ⅰ） molecular capsule, in which 3 Ag （Ⅰ） ions locate in the central line and 4 ligands wrap them inside, in which both N2 and N3 atoms in 1, 4-subsititued-1,2,3-triazole have coordinated to different Ag （Ⅰ） at the same time and PF6- or SbF6- ion only act as a counter ion to maintain the charge balance. The reaction mechanism of L1 with Ag （Ⅰ） ion in solution has been proposed from the evidence of 1H NMR and Mass spectrum as well as the DFT calculation.In Chapter 5, a series of new chelating ligands （V2-V8） with different aryl group at 4 position of 1,4-subsititued-1,2,3-triazole has been synthesized and characterized. In order to investigate the properties of the metal complexes influenced by the change of ligand structure, seven Ru （Ⅱ） complexes with formula [RuV1₇（bipy）2] （PF6）2 （V9-V15） have been designed, synthesized and characterized. The maximum UV-Vis absorption and fluorescence emissions of the ligands are in agreement with the conjugated length of the aryl group at 4-position of 1,2,3-triazole. The room temperature UV-Vis absorptions of the Ru （Ⅱ） complexes comprised ofÏ€-Ï€* transition and MLCT bands from ligands and the Ru （Ⅱ） metal. Andλmax of the MLCT bands exhibit little change when the aryl group the changes, but they show the obvious blue shift compared with the reference compound of [Ru（bipy）3]（PF6）2. Most of the Ru （Ⅱ） complexes mainly exhibit MLCT emission at room temperature except the complexes with anthracene or pyrene group in the ligand. The room-temperature luminescence intensity increases when the electron density of the aryl groups increase. However, all the complexes exhibit the MLCT emission at 77K while the intensity decreases with the increasing of the electron density of the aryl group. The calculation of their electrochemical band gaps indicated that the change of the aryl groups at 4 position of 1,2,3-triazole have very limited influence on the photo-physical properties of the complexes. Otherwise, structural simulation illustrates that the photophysical properties of complexes is related to the dihedral angle between the triazole group and aryl group in the ligands.In chapter 6, eight Re （Ⅰ） complexes with the formula of fac-[ReV1-8（CO）3]Cl （Ⅵ1-â…¥8） has been synthesized and their structure has been characterized by NMR, FT-IR, EA as well as single crystal structure analysis. Similar to the Ru（Ⅱ） complexes, the maximum UV-Vis absorption of the complexes are also in agreement with the conjugated length of the aryl group at 4-position of 1,2,3-triazole except a complex comes from the coordination of Re（Ⅰ） with a ligand with strong electron-withdrawn group TCF （2-（3-cyano-4,5,5-trimethylfuran-2（5H）-ylidene） malononitrile）. The room temperature and low-temperature （77K） photoluminescence properties of these complexes were strongly affected by the structural change of the aryl group at 4-position of 1,2,3-triazoleas as well as the dihedral angle between the triazole group and aryl group. And the solubility of the complex in common organic solvent becomes poor when the conjugated length of aryl group increases. The investigation for their electrochemical band gaps indicates that the change of the aryl group at 4 position has limited influence on the HOMO level, while the LUMO level will greatly reduced when electron-withdrawn group （TCF） has been introduced to the complex （Ⅵ8）.In Chapter 7, a tetra-dentate ligand （[2,2’-（4,4’-（2,5-bis（dodecyloxy）-1,4-pheny lene） bis-（1H-1,2,3-triazole-4,1-diyl）） bis-（methylene） dipyridine],â…¦1） has been synthesized based on the chelate structure of L1. The self-assembly ofâ…¦1 with CuCl2 yields a dinuclear complex （[Cu2（Ⅶ1）（CH3OH）2Cl4],â…¦2）. The single crystal structure is obtained and the UV-Vis absorptions have been measured. It is found thatâ…¦2 is a self-assembly coordination polymer via the unique O-H...C1 hydrogen bonds through the coordinated methanol and Cl- bonded to the neighboringâ…¦2 molecules. The magnetic measurement indicates that the very weak ferromagnetic interaction exists between the Cu-Cu cations in the chain at high temperature and an anti-ferromagnetic phase transition occurs at 30 K.From both experimental research and theoretical calculation, this work suggests that the "chelating effect" can effectively enhance the coordination ability of the "weak" N2 atom in 1,4-subsititued-1,2,3-triazoles. Sometimes the N2 and N3 atoms can coordinate to the metals at same time. Changing the substituted group at 4 positions of 1,2,3-triazole group can also tune the properties of the complexes. It indicates that the coordination of these ligands with different metals will afford an effective approach to construct new coordination architectures for a new kind of functionalized coordination materials.