title: Tuning the photoinduced electron-transfer thermodynamics in 1,3,5-triaryl-2-pyrazoline fluorophores: X-ray structures, photophysical characterization, computational analysis, and in vivo evaluation.
abstract: A series of donor-substituted 1,3,5-triaryl-2-pyrazoline fluorophores were structurally characterized by X-ray analysis, and their photophysical properties studied by steady-state absorption and emission spectroscopy. The photoinduced electron-transfer thermodynamics of the derivatives was estimated on the basis of the spectroscopic data and redox potentials of the fluorophores. The aryl substituents in the 1- and 3-position of the pyrazoline ring influence the photophysical properties of the fluorophores in distinctly different ways. The excited-state equilibrium energy DeltaE(00) is primarily influenced by changes of the substituent in the 1-position, whereas the reduction potential of the fluorophore is essentially determined by the 3-aryl group. Density functional calculations were used to probe the electronic structure and energy ordering of the emissive and the electron-transfer state. The results from the computational analysis agree qualitatively well with the experimental data. In addition, we have evaluated a water soluble pyrazoline derivative in vivo as a potential intracellular pH probe. Membrane permeability, low toxicity, and high quantum yield render the fluorophore attractive for biological applications.
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State Street, Atlanta 30332, USA. fahrni@chemistry.gatech.edu
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Fahrni
authors.forename: Liuchun
authors.initials: L
authors.lastname: Yang
authors.forename: Donald G
authors.initials: DG
authors.lastname: VanDerveer
mesh_terms: D002463:Cell Membrane Permeability; D018360:Crystallography, X-Ray; D004583:Electrons; D005456:Fluorescent Dyes / Q000737:chemistry* / Q000493:pharmacokinetics; D006367:HeLa Cells; D006801:Humans; D008081:Liposomes / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010777:Photochemistry; D011199:Potentiometry; D011720:Pyrazoles / Q000737:chemistry* / Q000493:pharmacokinetics; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013194:Staining and Labeling; D013816:Thermodynamics
chemical_list: D005456:Fluorescent Dyes; D008081:Liposomes; D011720:Pyrazoles