Ice Bath Synthesis Of Schiff Base Compounds And Their Structural Performance Research

Schiff bases showed important chemical and biological significance because of their flexible characteristics,and have attracted considerable attention of chemists.A series of Schiff bases were synthesized by reacting substituted aromatic aldehydes and primary amines under ice bath,four of which were first reported.The chemical structures of these compounds were confirmed by means of IR and ¹HNMR.The compouds were detected through UV absorption and fluorescence spectrum in solution and solid state,and the relationship between the molecule structure and the spectrum was also studied.The results show that an OH group in an ortho- position in the salicylaldehyde is the necessary condition of schiff base compounds which possess strong fluorescence properties;In the polar solvent,the exist of an OH group in an ortho or para position can cause the change of structure of bis-schiff bases; compared with the solid state,the schiff base's fluorescence is weaker when in the solvent and exhibits emission in the 317nm and 400nm.In this study,the title compound was synthesized by reactions of the o-phenyldiamine with 5-F-salicylaldehyde under ice bath.Its structure has been investigated by X-ray single crystal diffraction.It reveals that the compound belongs to monoclinic P2(1)/c space group,a=6.0938(8), b=16.347(2),c=94.474(2),V=1651.9(4),Z=4,D_c=1.417andμ=0.11. The Zn(Ⅱ)complex has also been prepared and characterized by the analytical and spectroscopic methods.According to the characterization data,the structure of the complex was interpreted and its fluorescence properties was also investigated.Bis-[2-(2-chloro-4-fluorophenyl)-1H-Benzimidazole]-hydrate has been synthesized from bis-Schiff base.The results determined by XRD reveals that the complex crystallizes in Triclinic,space group P1,with a =7.592(2),b=7.595(2),c=11.886(3)(?),V=574(3)(?)³,M_r=352.33,D_c =1.478g/cm³,μ(MoKa)=0.33 mm^-1,F(000)=262,Z=1,the final R= 0.090 and wR=0.209.The crystal structure is formed with two benzimidazole molecules,which are linked by a water molecule as center, similar to the complex of benzimidazole.The reaction mechanism was also discussed by changing reaction conditions.It is demonstrated that benzimidazole can only be formed from Schiff base effectively when o-hydroxyl group does not exist in benzaldehyde.