0000000000471530
AUTHOR
J. Arturo Santaballa
Combined Theoretical and Experimental Study of the Photophysics of Asulam
The photophysics of the neutral molecular form of the herbicide asulam has been described in a joint experimental and theoretical, at the CASPT2 level, study. The unique π → π* aromatic electronic transition (f, ca. 0.5) shows a weak red-shift as the polarity of the solvent is increased, whereas the fluorescence band undergoes larger red-shifts. Solvatochromic data point to higher dipole moment in the excited state than in the ground state (μ(g)μ(e)). The observed increase in pKa in the excited state (pKa* - pKa, ca. 3) is consistent with the results of the Kamlet-Abboud-Taft and Catalán et al. multiparametric approaches. Fluorescence quantum yield varies with the solvent, higher in water (…
On the Low-Lying Excited States ofsym-Triazine-Based Herbicides
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…
Energy landscapes in diexo and exo/endo isomers derived from Li2B12H12
Abstract In the pursuit of detecting the first endohedral polyhedral borane complex, we report a quantum-chemical computational study of energy landscapes for diexo isomers derived from Li 2 B 12 H 12 and the exo/endo isomer Li@{LiB 12 H 12 }. Geometries, electronic structure and energy barriers are computed for the interconversion between diexo isomers and the exo / endo isomer, the latter leading to a thermal injection / ejection mechanism of Li + from outside / inside the complex [LiB 12 H 12 ] − .