Synthesis Of Fluorescent Small Molecule Compounds Based On Imidazole Ring And Determination Of Their Luminescent Properties

Imidazole as an organic fluorescent small molecule is one of the most importantheterocyclic compounds. Because it contains rich π electron and easily transmitselectrons and protons, these make imidazoles possess good luminescent property.Furthermore, imidazole ring is a non-center symmetrical structure that is π electrondeficient, which may link to strong electron-withdrawing groups and have excellentproperties of electronic transmission. Imidazole-based compounds are excellentorganic non-linear optical materials.Firstly, a series of2,4,5-tri or1,2,4,5-tetrasubstituted imidazoles were synthesizedby embellishing the molecular of2,4,5-trifurylimidazole such as conjugation,planarity.2,4,5-trisubstituted imidazoles were synthesized in the condition of usingaromatic diketone, aromatic aldehyde and ammonium acetate as raw materials undersolvent-free conditions through microwave assisted method. This process has shortreaction time, fast reaction rate, easy work-up.1,2,4,5-tetrasubstituted imidazoles wereobtained staring from tri-substituted and biphenyl benzyl dichloride in the presence ofphase transfer catalyst and benzene as solvent by N–alkylation reaction. Thestructures of all synthesized products were characterized by MS, NMR, IR. Then thesolid fluorescence spectrum were tested, quantum yields were calculated. Therelationship between molecular structure and luminescence properties were discussed.Secondly, A solvent-free microwave-assisted four-component synthesis of1,2,4,5-tetrasubstituted imidazoles was studied. Imidazole derivatives were preparedin moderate to good yields by condensation of aryl-diketone, benzaldehydederivatives, p-phenylenediamine and ammonium acetate in the presence of solidsupport silica gel and catalyst Keggin-H3[PW12O40]. Effects of four components alongwith catalyst loading, irradiation time on the yields were investigated. Also, thestructures of synthesized compounds were characterized by FT-IR, HRMS,1H NMR and13C NMR spectroscopy.At last, the solid fluorescence spectrum were tested, quantum yields werecalculated. Besides, the emission and fluorescence quantum efficiency of thesynthesized compounds in solution was sensitive to the polarity of the solvents.