27 research outputs found
Computational Study of Copper(II) Complexation and Hydrolysis in Aqueous Solutions Using Mixed Cluster/Continuum Models
Spontaneous Symmetry Breaking Facilitates Metal-to-Ligand Charge Transfer: A Quantitative Two-Photon Absorption Study of Ferrocene-phenyleneethynylene Oligomers
Change
of the permanent molecular electric dipole moment, Δμ,
in a series of nominally centrosymmetric and noncentrosymmteric ferrocene-phenyleneethynylene
oligomers was estimated by measuring the two-photon absorption cross-section
spectra of the lower energy metal-to-ligand charge-transfer transitions
using femtosecond nonlinear transmission method and was found to vary
in the range up to 12 D, with the highest value corresponding to the
most nonsymmetric system. Calculations of the Δμ performed
by the TD-DFT method show quantitative agreement with the experimental
values and reveal that facile rotation of the ferrocene moieties relative
to the organic ligand breaks the ground-state inversion symmetry in
the nominally symmetric structures
Calculation of Solvation Free Energies of Charged Solutes Using Mixed Cluster/Continuum Models
First computational evidence of a competitive stepwise and concerted mechanism for the reduction of antimalarial endoperoxides
We study structural analogues of endoperoxides belonging to the family of G factors which present moderate to good antimalarial activity. Their biological activity is related to the reduction and cleavage of the O-O bond. Generally, the O-O bond reduction of model endoperoxides, as well as artemisinin, occurs by a concerted
dissociative electron transfer (ET) mechanism. For the G3 and G3Me compounds, the experimental counterpart indicates an unexpected competition between a concerted and a stepwise mechanism, but no intermediate species can be isolated. We thus perform DFT studies on the reduction of G3 and G3Me compounds. We confirm the formation of an intermediate radical anion followed by cleavage of the O-O bond in a second
step. We characterize the stable conformations for the radical anions G3
•- and G3Me•- resulting from the ET and the associated reaction pathway. We also calculate the reorganization energy upon ET in relation to the Marcus theory using the DFT method. These results provide valuable insight into understanding the biological activity of G-factor endoperoxides as potential therapeutic antimalarial agents