title: Absorption and fluorescence emission attributes of a fluorescent dye: 2,3,5,6-tetracyano-p-hydroquinone.
abstract: Four cyano groups have been substituted on the aromatic ring of p-hydroquinone (2,3,5,6-tetracyanohydroquinone) in order to study the enhanced photoacidity of this molecule. The acid-base equilibria have been studied using absorption (for ground state pKa) and fluorescence (excited state pKa) spectra. Three distinct species (neutral, anionic and dianionic forms) were observed in the ground state and only two species (anionic and dianionic forms) were found in the excited state when studied at different pH/Ho in water. Absorption and emission characteristics were studied in various organic solvents, including protic and aprotic solvents. Deprotonation was also investigated using binary mixtures. It has been revealed that absorption and emission spectra are considerably changed with change in media. Proton transfer to the solvent has been observed in various solvents.
authors.affiliation: Department of Chemistry & Biochemistry, University of Agriculture Faisalabad, Faisalabad, Pakistan. zahid595@gmail.com
authors.forename: Muhammad
authors.initials: M
authors.lastname: Zahid
authors.forename: Günter
authors.initials: G
authors.lastname: Grampp
authors.forename: Asim
authors.initials: A
authors.lastname: Mansha
authors.forename: Ijaz Ahmad
authors.initials: IA
authors.lastname: Bhatti
authors.forename: Sadia
authors.initials: S
authors.lastname: Asim
mesh_terms: D000042:Absorption; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006873:Hydroquinones / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014867:Water / Q000737:chemistry
chemical_list: C586077:2,3,5,6-tetracyano-p-hydroquinone; D005456:Fluorescent Dyes; D006873:Hydroquinones; D009570:Nitriles; D012997:Solvents; D014867:Water; C031927:hydroquinone