Synthesis And Spectral Properties Of Amino Acetylimidazole Fluorescent Molecular Probes

In this paper, five targets product containing 1H-phenanthro[9,10-d]imidazole or arylimidazolesmoiety as the fluorophores and ammonium acetate, ammonium ethylene diamine and ammonium acetohydrazide as the as a potential binding site for the metal ions, respectively. The five compound are potassium 2-[N-ethoxyformyl methyl-N-(4-1H-phen-anthro[9,10-d]imidazol-2-yl)phenyl]amino acetate(H1), potassium 4-(4,5-diphenyl-1H-imidazol-2-yl)anilinyl acetate(H2), potassium 4-(1,4,5-triphenyl-1H-imidazol-2-yl)anilinyl acetate(H3), 2-{4-[N,N-bis-(2-aminoethylcarbamoylmethyl)-phenyl]}-1H-phenanthro[9,10-d]imidazole(H4), 2-{4-[N,N-bis-(2-hydrazinoacetyl)-phenyl]}-1H-phenanthro[9,10-d]imidazole(H5). These target molecules were synthesized and characterized successfully through 1H NMR, 13 C NMR, FTIR and MS methods.Fluorescence spectra of ammonium acetate H1, H2, H3 were tested at different p H between 2.0 to 8.0 in Tris–HCl buffered solution. At the same time, the selectivity, response time and reversibility of ammonium acetate H1, H2, H3 were tested to H+. Fluorescence intensity of compound H1, H2, H3 diminished with pH increasing from 2.0 to 8.0. Besides, the solution changed from blue to green between acidic and alkaline at the excitation wavelength of 365 nm under the UV light.In Tris–HCl buffer solution(pH = 7.4), four arylimidazoles ammonia acetate H3 is a highly sensitive and selective chemosensor for Cu2+. Moreover, according to Job’s plot, 2:1 stoichiometry complex between H3 and Cu2+ is formed. Compound H4 could recognize Ag+ with remarkable naked visual differences in DMF/H2O(1:9, v/v, HEPES 20 mM, pH = 7.4) solution. Upoun addition of Ag+, there is an obvious change in color to yellow was observed with the appearance of a new absorption peak at 422 nm. Fluorescence titration, ESI-MS, and Job plot analysis manifest a 1:1 binding mode. The fluorescence intensity of H5 and H5–Ni2+ diminishes and enhances in the presence of Ni2+ and Al3+ ions, respectively. H5 interacts with Ni2+ resulting in fluorescence intensity completely quenching through a 1:1 binding mode by the ESI-MS and Job plot analysis. Moreover, Al3+ displaces Ni2+ from the H5–Ni2+ complex acting as a turn on fluorescence sensor.