title: Speciation, luminescence, and alkaline fluorescence quenching of 4-(2-methylbutyl)aminodipicolinic acid (H2MEBADPA).
abstract: 4-(2-Methylbutyl)aminodipicolinic acid (H(2)MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pK(a)'s) and photophysical measurements. The pK(a)'s were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA(2-) is appreciably emissive. The fluorescence of MEBADPA(2-) has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. Utilizing the determined pK(a)s and quenching constants, the fluorescent intensity of MEBADPA(2-) has been successfully modeled as a function of pH.
authors.affiliation: Department of Chemistry, San José State University, 1 Washington Square, San José, California 95192-0101, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Ingram
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Dunlap
authors.forename: Richard
authors.initials: R
authors.lastname: Dipietro
authors.forename: Gilles
authors.initials: G
authors.lastname: Muller
mesh_terms: D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D049449:Luminescence; D010848:Picolinic Acids / Q000138:chemical synthesis / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: C568741:4-(2-methylbutyl)aminodipicolinic acid; D010848:Picolinic Acids; C004860:dipicolinic acid