title: Emission switching of 4,6-diphenylpyrimidones: solvent and solid state effects.
abstract: The photophysics of 1-ethyl-4,6-bis(4-methoxyphenyl)-2(1H)-pyrimidone (1) and 1-ethyl-4,6-bis(4-(dimethylamino)phenyl)-2(1H)-pyrimidone (2) were investigated to determine the mechanisms of emission switching in response to protonation. UV-vis and steady state emission spectroscopy of the protonated and unprotonated forms across a range of solvents reveal the polarity dependence of the vertical excitation energies. Emission lifetimes and quantum yields show the solvent dependency of the excited states. Emission enhancements were observed in polyethylene glycol solutions and in the solid state (both thin film and single crystal), demonstrating the role of intramolecular rotation in thermal relaxation of the excited states. TD-DFT calculations provide insights into the excited state geometries and the role of intramolecular charge transfer. The collected data show that emission of diphenylpyrimidones can be modulated by four factors, including the identity of the electron-donating auxochrome, protonation state, solvent polarity, and viscosity.
authors.affiliation: Department of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables, Florida 33146, United States.
authors.forename: Edward
authors.initials: E
authors.lastname: Adjaye-Mensah
authors.forename: Walter G
authors.initials: WG
authors.lastname: Gonzalez
authors.forename: David R
authors.initials: DR
authors.lastname: Bussé
authors.forename: Burjor
authors.initials: B
authors.lastname: Captain
authors.forename: Jaroslava
authors.initials: J
authors.lastname: Miksovska
authors.forename: James N
authors.initials: JN
authors.lastname: Wilson
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011092:Polyethylene Glycols / Q000737:chemistry; D011744:Pyrimidinones / Q000737:chemistry*; D011789:Quantum Theory; D012996:Solutions; D012997:Solvents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005456:Fluorescent Dyes; D011744:Pyrimidinones; D012996:Solutions; D012997:Solvents; D011092:Polyethylene Glycols