title: Synthesis, Spectroscopic Characterization and DFT/TD-DFT Calculations of new Fluorescent Derivatives of Imidazo[4',5':3,4]Benzo[c]Isoxazole.
abstract: An increasingly wide variety of fluorescent compounds is used in biotechnology, genomics, immunoassays, array technologies, imaging, and drug discovery. Therefore, synthesis of fluorophores with novel structural features can be interesting and useful in various fields. In this paper, four new fluorescent heterocyclic compounds with high quantum yields are introduced. These new fluorophores are synthesized in moderate to high yields via regioselective nitration of 3-alkyl-8-(4-chlorophenyl)-3 H-imidazo[4',5':3,4]benzo[c]isoxazoles. The latter compounds are obtained from the reaction of 1-alkyl-5-nitro-1 H-benzoimidazoles with (4-chlorophenyl)acetonitrile in basic MeOH solution. Physical spectral (UV-vis, IR, (1)HNMR, (13)C NMR, NOESY and fluorescence) and analytical data have established the structures of synthesized compounds. The fluorescence properties of new fluorescent heterocyclic compounds are studied. The fluorescence of all compounds is very intense and fluorescence quantum yields are high (> 0.52). Density functional theory (DFT) calculations are performed to provide the optimized geometries, relevant frontier orbitals and the prediction of (1)H NMR chemical shifts for confirming the exact structure of fluorescent compounds. Calculated electronic absorption spectra were also obtained by time-dependent density functional theory (TD-DFT) method.
authors.affiliation: Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran.
authors.forename: Shirin
authors.initials: S
authors.lastname: Ramezani
authors.affiliation: Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran. mehdipordel58@yahoo.com.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Pordel
authors.affiliation: Department of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran.
authors.forename: Safarali
authors.initials: S
authors.lastname: Beyramabadi
mesh_terms: D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D007555:Isoxazoles / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors
chemical_list: D005456:Fluorescent Dyes; D007093:Imidazoles; D007555:Isoxazoles
keywords: 3 H-Imidazo[4′,5′:3,4]benzo[c]isoxazole; Density functional theory; Emission and absorption spectra; Fluorescence; NOESY