title: Push-pull fluorophores based on imidazole-4,5-dicarbonitrile: a comparison of spectral properties in solution and polymer matrices.
abstract: Spectral properties of novel type of fluorophores consist of a π-conjugated system end-capped with an electron-donating N,N-dimethylaminophenyl group and an electron-withdrawing imidazole-4,5-dicarbonitrile moiety were examined. An additional π-linker separating these two structural units comprises simple bond (B1P), phenyl (B2B), styryl (B3S) and ethynylphenyl (B4A) moieties. The absorption and fluorescence spectra were taken in cyclohexane, chloroform, acetonitrile, methanol and in polymer matrices such as polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The longest-wavelength absorption band was observed in the range of 300 to 400 nm. Intense fluorescence with quantum yields of 0.2 to 1.0 was observed in cyclohexane, chloroform and in polymer matrices within the range of 380 to 500 nm. The fluorescence was strongly quenched in neat acetonitrile and methanol. The fluorescence lifetimes are in the range of 1-4 ns for all measured fluorophores. The large Stokes shift (4,000 to 8,000 cm(-1)) indicates a large difference in the spatial arrangement of the chromophore in the absorbing and the emitting states. The observed fluorescence of all fluorophores in chloroform was quenched by 1-oxo-2,2,6,6-tetramethyl-4-hydroxy piperidine by the diffusion-controlled bimolecular rate (cca 2 × 10(10) L mol(-1) s(-1)). Polar solvents such as acetonitrile and methanol quenched the fluorescence as well but probably via a different mechanism.
authors.affiliation: Department of Photochemistry of Polymers Slovak Academy of Sciences, Polymer Institute, Center of Excellence GLYCOMED, Dúbravská cesta 9, 845 41 Bratislava, Slovakia. upoldan@savba.sk
authors.forename: Martin
authors.initials: M
authors.lastname: Danko
authors.forename: Pavol
authors.initials: P
authors.lastname: Hrdlovič
authors.forename: Jiří
authors.initials: J
authors.lastname: Kulhánek
authors.forename: Filip
authors.initials: F
authors.lastname: Bureš
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011789:Quantum Theory; D012996:Solutions; D013050:Spectrometry, Fluorescence
chemical_list: D005456:Fluorescent Dyes; D007093:Imidazoles; D009570:Nitriles; D011108:Polymers; D012996:Solutions; C568576:imidazole-4,5-dicarbonitrile