title: On the low-lying excited states of sym-triazine-based herbicides.
abstract: We report a joint computational and luminescence study on the low-lying excited states of sym-triazines, namely, 1,3,5-triazine (1) and the ubiquitous herbicides atrazine [6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine (2)] and ametryn [6-methylthio-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine (3)]. Geometrical structures, energetics, and transition and state properties of I and 2 were computed at the TD-DFT, CASSCF, and CASPT2 levels of theory. The fluorescence and phosphorescence emission spectra, lifetimes, and fluorescence quantum yields were measured for the three compounds, and from these, the energies of the lowest excited states and their corresponding radiative rates were determined. The predictions from CASPT2 calculations are in good agreement with the experimental results obtained from the luminescence studies and allow the interpretation of different absorption and emission features.
authors.affiliation: Instituto de Química Física Rocasolano, Consejo Superior de Investigaciones Cientfficas Serrano 119, 28006 Madrid Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Oliva
authors.forename: M Emilia D G
authors.initials: ME
authors.lastname: Azenha
authors.forename: Hugh D
authors.initials: HD
authors.lastname: Burrows
authors.forename: Rita
authors.initials: R
authors.lastname: Coimbra
authors.forename: J Serxio
authors.initials: JS
authors.lastname: Seixas de Melo
authors.forename: L
authors.initials: L
authors.lastname: Moisés Canle
authors.forename: M Isabel
authors.initials: MI
authors.lastname: Fernández
authors.forename: J Arturo
authors.initials: JA
authors.lastname: Santaballa
authors.forename: Luis
authors.initials: L
authors.lastname: Serrano-Andrés
mesh_terms: D000042:Absorption; D001280:Atrazine / Q000737:chemistry; D002627:Chemistry, Physical / Q000379:methods; D006540:Herbicides / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000737:chemistry; D008956:Models, Chemical; D008962:Models, Theoretical; D015394:Molecular Structure; D009991:Oscillometry; D011312:Pressure; D012984:Software; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013696:Temperature; D014227:Triazines / Q000737:chemistry
chemical_list: D006540:Herbicides; D007202:Indicators and Reagents; D014227:Triazines; D001280:Atrazine