Syntheses And Properties Of One Dimensional Ferrous Coordination Polymers Based On N-salicylicaldehyde 4-Amino-1,2,4-triazole

In recent years, magnetic materials with spin crossover behavior have attractive application prospects, and have become one of the hot topics in the field of materials.One of the difficulties in the field of magnetic materials is to design appropriate molecules with spin crossover behavior at room temperature. One of the systems of spin crossover at room temperature is iron(II)-triazole. According to crystal field theory, when the splitting energy is near to electron pairing energy in the ligand field, the electron arrangment can be transfered by varying external condition such as light, thermal,pressure, accompanying with a convert between the high-spin (HS) and low-spin (LS)states in these materials. In this paper, a series of ferrous one-dimensional chain complexes with spin crossover behavior were synthesized by using N-salicylaldehyde-4-amino-1,2,4-triazole derivatives as ligands. And the magnetic properties were studied.In chapter 1, we give a brief introduction about current research and development of magnetic materials and schiff bases. Besides, we make a brief review about properties and applications of spin-crossover (SCO) complexes and photochromism. Finally, we explicate the research background and innovation point of this thesis.In chapter 2, we synthesized and characterized N-Salicylidene-4-amino-1 ,2,4--triaozole derivatives with 1,2,4-triazole as the ligands. The solid of N-(3-tertbutyl-salicy lidene)-4-amino-1,2,4-triazole(3tBusaltrz) and N-(3,5-ditertbutylsalicylidene)--4-amino-1,2,4-triazole(35tBusaltrz) were irradiated with a 365 nm UV lamp, the sample is white and turns to orange yellow and to yellow after irradiation respectively,and it's colour varies from yellow to white after gentle heating. The UV-vis diffuse reflectance spectrophotometry proved that 3tBusaltrz and 35tBusaltrz had enol-keto tautomerism. The methanol solution of N-(3-methoxysalicylidene)-4-amino-1,2,4-triazole (3MeOsaltrz), N-(4-methoxysalicylidene)-4-amino-1,2,4-triazole (4MeO-saltrz), N-(5-methylsalicylidene)-4-amino-1,2,4-triazole (5Mesaltrz), N-(5-chlorosali-cylidene)-4-amino-1,2,4-triazole (5Clsaltrz) and N-salicylidene-4-amino-1,2,4-triazole(Saltrz) were illuminated with a 365 nm UV light, the UV-vis absorption spectram show that the intensity of absorption peaks attenuated with the increase of the irradiation time and no longer changed after a certain time, which indicative of the existence of enol-keto tautomerism in solution. Fluorescence spectrometry shows N-salicylaldehyde--4-amino-1,2,4-triazole derivatives had fluorescence activity.In chapter 3, these compound 1-17 were prepared as powders after reaction of N-salicylidene-4-amino-1,2,4-triazole with ferrous salts of different anions (ClO4-, BF4-,Br-,NO3-): [Fe(3tBusaltrz)0.22(4NH2trz)2.78](ClO4)2·H2O (4NH2trz = 4-amino-1,2,4--triazole) (1),[Fe(35tBusaltrz)0.083(4NH2trz)2.917](ClO4)2·H2O (2),[Fe(3tBusaltrz)0.07-(4NH2trz)2 93](BF4)2·0.75H2O (3),[Fe(35tBusaltrz)0.2(4NH2trz)2.8](BF4)2·H2O (4),[Fe-(3tBusaltrz)0.25(4NH2trz)2.75]Br2·H2O (5),[Fe(35tBusaltrz)0.75(4NH2trz)2.25]Br2·1.5H2O(6),[Fe(3tBusaltrz)0.4(4NH2trz)2.6](NO3)2·0.5H2O (7),[Fe(35tBusaltrz)0.42(4NH2trz)2.58]-(N03)2·H20 (8), [Fe(5Mesaltrz)3](C104)2·7H2O(9),[Fe(5Mesaltrz)3](BF4)2·3.5H2O(10),[Fe(5Mesaltrz)3]Br2·3.5H2O (11),[Fe(5Mesaltrz)3](NO3)2· 10H2O (12), [Fe(saltrz)3]-(N03)2·9H20 (13), [Fe(5Clsaltrz)3](ClO4)2-5H20 (14), [Fe(5Clsaltrz)3](BF4)2-3H2O (15),[Fe(5Clsaltrz)3]Br2.4H2O (16),[Fe(5Clsaltrz)3](NO3)2·nH2O (17). The magnetic data showed that compounds 1-4 and compounds 9-17 had a slow one-step spin crossover in the range of 2 to 300 K; compounds 5-8 have spin crossover behavior at room temperature or near room temperature in the range of 200 K to 393 K. Compound 7-0.5dH (compound 7 loses 0.5 molecular water) reveals an abrupt single step transition with a hysteresis loop of width 17 K (T1/2??291 K, T1/2? = 318 K); compound 8-1dH(compound 8 loses one molecular water) also reveals an abrupt single step transition with a hysteresis loop of width 16 K (T1/2?=299 K,T1/2?= 318 K).In chapter 4, the conclusion of this paper and expectation were made.