Syntheses, Crystal Structures And Characterization Of The Complexes Of 3-Ethyl-4-Phenyl-5-(2-Pyridyl)-1, 2, 4-Triazole

1,2,4-Triazoles have gained considerable attention in recent years. Because they can form complexes with transition-metal ions, and some of them exhibit spin crossover behavior, which can be used potentially to molecular electronic devices. In order to synthesize and research the novel complexes of transition-metal ions with 1,2,4-triazoles, the complexes of copper(II) and manganese(II) ions with 3-ethyl-4-phenyl-5-(2-pyridyl)-1,2,4-triazoles have been synthesized and characterized, and their crystal structures were determined by X-ray analyses. The thesis is composed of the following three sections:Part I. 3-ethyl-4-phenyl-5-(2-pyridyl)-1,2,4-triazole(L) was synthesized by several-step reactions fromα-picoline, and was confirmed by IR,1H-NMR and MS spectra. Part II. The complexes of [Cu2(μ-L)₂Cl₄], [CuL2(Sal)2]·H2O and [Mn₂L₂(μ-Cl)₂Cl₂(H₂O)₂] have been prepared, and the crystal structures of L, [Cu2(μ-L)₂Cl₄], [CuL2(Sal)2]·H2O and [Mn₂L₂(μ-Cl)₂Cl₂(H₂O)₂] were determined by X-ray analyses. The crystal structure of L shows that the three aryl rings of 1,2,4-triazole ring,pyridine ring and benzene ring do not share a common plane. The metal ions of the dinuclear copper(II) complex of [Cu₂(μ-L)₂Cl₄] are linked by two N¹,N² 1,2,4-triazole bridges,and the central Cu(II) ions have distorted trigonal bipyramid geometries. The central Cu(II) ion of [CuL2(Sal)2]·H2O has a centrosymmetric and distorted tetragonal-octahedral geometry. The metal ions of the dinuclear manganese(II) complex of [Mn₂L₂(μ-Cl)₂Cl₂(H₂O)₂] are bridged by two chlorine atoms, and the central Mn(II) ions have distorted tetragonal-octahedral geometries.Part III. The ESR spectrum of [CuL2(Sal)2]·H2O at low temperature and the magnetic susceptibilities of [Cu₂(μ-L)₂Cl₄] are measured. The electronic absorption spectra in thin solution and thermal gravimetric analyses of the three complexes were also measured. As the central Cu(II) ion of [CuL₂(Sal)₂]·H₂O is anisotropic, it gives three g-values in the ESR spectra. The g-values are g1=2.2603, g2=2.0712, g3=2.0342. The magnetic data of [Cu₂(μ-L)₂Cl₄] shows that there are antiferromaganetic interactions between the copper(II) ions. Thermal gravimetric analyses shows that as temperature rise, the complexes first lose their crystal water or coordinate water, and then decompose gradually at higher temperature.