Study On Synthesis Of Bithiophenyl-bridged Bisterpyridine And Its Complex And N-N Coupling In The Presence Of Cucl₂

1. Synthesis and spectroscopic behavior of bithiophenyl bridged bisterpyridine and its complexTerpyridine is a class of important N-heterocycles which play important roles in modern scientific and technical field. In this thesis, bithiophenyl bridged bisterpyridine (BTTPY) was designed and synthesized from 2,5-dibromothiophene in a total yield of 12.5% via acylation, modified Kr?hnke reaction and Suzuki coupling. The prepared BTTPY was characterized by NMR, MS and IR.The spectroscopic behaviors of BTTPY and its monomer TTPY in nine organic solvents were studied. In non-acidic solvents, a maximum absorption band was detected around 280 nm for TTPY and 392 nm for BTTPY which can attrib to theπ-π* transition. Due to the D-A (donor-acceptor) nature of TTPY, it shows weaker fluorescence in more polar solvents while the fluorescence of BTTPY which consists a symmetric structure is insensitive to the polarity of solvents. In acidic solvent, a red shift was detected for both compounds owing to the conformation change and better conjugated structure caused by the strong protonation. The fluorescence was also sharply weakened due to intramolecular charge transfer.The interactions between TTPY and Co2+, BTTPY and metal cations (Co2+, Ni2+, Zn2+, Cd2+, Cu2+) were studied by UV-vis and fluorescence titration, and the saturated complexation ratio for TTPY and Co2+ was identified as 2:1, and 1:1 for BTTPY and metal cations(Co2+, Ni2+, Zn2+, Cd2+, Cu2+). An organometallic polymer was formed when equivalent metal ion was added to the BTTPY solution.The organometallic polymer was obtained by refluxing BTTPY and metal salts in methanol or acetic acid, and it was then studied by atomic force microscopy (AFM). The nanoparticles with rod like structure were found on the film of Zn2+·BTTPY complex which were generated due to the line nature of the polymer and strongπ-πinteractions of the polymer chains.2. Study on N-N Coupling in the Presence of CuCl2The symmetric tetrasubstitued hydrazine was obtained via the CuCl2-promoted oxidative N-N coupling of lithium amines and 14 of secondary amines was carefully studied and 11 of them can undergo N-N coupling, however, only 6 of the substituted hydrazine was isolated due to the weak stability of the product, and the yields varies from 17 to 75%. The coupling reaction is sensitive to the steric hinder and substitution effect. Amines with strong electron-withdrawing groups can't undergo coupling progress due to the high stability of the amine lithium salts which was proved by the coupling reaction of 4-(methylamino)benzonitrile and N-methyl-4-nitrobenzenamine. Hinder groups reduce the coupling yield or prevent the coupling progress, and the coupling yield of N-ethylanilines was evidently lower than coupling yield of the corresponding N-methylanilines. Moreover, the poor stability of some hydrazine which can undergo decomposition/rearrangement under chromatography or GC-MS or illumination condition also reduces the coupling yield. The best working condition was that at -80℃, the secondary amines were treated with 1.2 equiv of n-BuLi, and then 1.5 equiv of copper chloride was added.CuCl2-promoted C-N coupling was also detected when excess n-BuLi was added, and then dibutylamine and N-ethylaniline was selected as the substrates to study this reaction, and C-N coupling can take place effectively when excess butyl lithium was added. It is found that high reaction temperature could increase the yield of C-N coupling.