Synthesis, Structures And Structure-property Relationship Of Substituted 1,2,4-triazoles And Their Functional Coordination Compounds

The complexes containing 1,2,4-triazole ligands which take various coordination modes possess specialized optical and magnetic properties. Thus their syntheses, structures and functionalities attract much interest. This thesis aims at the design and synthesis 1,2,4-triazole ligands with different substitutents: 1H-1,2,4-triazole (Htrz); 3-amino-1H-1,2,4-triazole (Httr); 3-(1,2,4-triazole)-1H-1,2,4-triazole(H2trtr). The three kinds of 1,2,4-triazoles have been determined by molting points, FT-IR, fluorescence, and diffuse reflectance spectra. The three corresponding series of transition metal complexes were obtained through diffusing, solution and hydrothermal methods, and then characterized by EA, FT-IR, single crystal X-ray diffraction method and fluorescence. A primary exploration to the structure-property relationship has been summarized based on fluorescence.1.Zinc and cadmium coordination polymers containing Htrz, [Zn(trz)Cl]_n (1) and [Cd(Htrz)Br₂] (2), were synthesized by diffusing method. In 1, the deprotoned trz^- adoptingμ₃-1κN:2κN: 4κN fashion connects Zn²⁺ to form 6- and 16-membered rings, whose fuse produces a 2D grid. While in 2, Htrz takesμ₂-1κN:2κN fashion to link Cd²⁺ into a 1D chain.2. Three 2D layered compounds containing Httr, [Zn(ttr)Cl]_n(3), [Zn₂(ttr)₂(OAc)₂]n (4) and[Mn₂(ttr)₂(OAc)₂]_n·nH₂O (5), were synthesized by diffusing or hydrothermal method. Similarto 1, the deprotonated ttr^- in 3 and 4 adoptsμ₃-1κN:2κN:4κN fashion to connect Zn²⁺ to form a coplanar 6-membered hexagonal ring and a 16-membered chair-like one. The fuse of the two kinds of edge-sharing rings produces a 2D grid. In 3, a supramolecular architecture is fabricated by H-bonds linking with the neighboring plane-symmetry layers. While in 4, C3-H…πinteractions take the place of H-bonds. In 5, Htrz adoptsμ₂-1κN:4κN fashion bridging Mn²⁺ into two kinds of edge-sharing 16-membered rings, whose fuse produces a wave-like 2D layer, and are further fabricated into a supramolecular architecture by H-bonds. The emissions of 3-5 recorded at room temperature locate at 416 nm (λ_ex= 350 nm), 443 nm (λ_ex= 344 nm) and 419 nm (λ_ex= 350 nm). Compared to free Htrz (λ_ex = 423 nm,λ_ex= 350 nm), the emissions of 3 and 5 can be assigned toπ…π^* intra-ligand transition of ttr^-, and the one of 4 to LMCT.3. With H₂trtr as ligand, two monomeric complexes [Zn(H₂trtr)₂(H₂O)₄](NO₃)₂·2H₂O (6) and [Mn(H₂trtr)₂(H₂O)₄](ClO₄)₂ (7), one 2D polymer [Zn(trtr)₂]_n (8) were obtained from solution reaction, and one 3D framework [Cd(trtr)₂]_n (9) from hydrothermal method. In 6 and 7, monodentate H₂trtr ligands coordinate metal centers with 1-positioned N atom to form isolated mononuclear complexes. In 8, the deprotoned trtr^2- takingμ₂-1κN:1'κN fashion connects with Zn²⁺ into a 2D grid. Differently, the deprotoned trtr2" in 9 adoptsμ₃-1κN:4κN:1'κN fashion to link Cd²⁺ into a 3D framework. The emissions of 6, 7, 9 recorded at room temperature locate at 349 nm (λ_ex= 285 nm), 358 nm (λ_ex= 293 nm) and 409 nm (λ_ex= 281 nm). Compared to free H₂trtr (λ_ex = 427 nm,λ_ex= 360 nm), the emissions of 6 and 7 can be assigned to LMCT, and the one of 9 toπ…π^* intra-ligand transition of trtr^2-.The summary on the structural features and fluorescence indicates that electron withdrawing/donating substituents on 1,2,4-triazole rings play a significant role in not only theelectronic configuration, which relies on the conjugate correlation with the 1,2,4-triazole ring.It is also found that metal can impart its secondary effect on the luminescence. The research inthis thesis shows it is possible to achieve organic blue emission molecular materials with band locating in 435～480 nm by the controlled inputting electron withdrawing/donating substituents and the modification of metal centers...