The DFT local reactivity descriptors of α-tocopherol

Abstract

The calculations of local reactivity descriptors, the electron donor Fukui function f(-)(r), the average local ionization energy Ī(r), the Fukui function dual descriptor f((2))(r), and the electron acceptor Fukui function f(+)(r) for α-tocopherol, the main biologically active form of vitamin E for antioxidant reactions in phospholipid membranes, is presented. The calculations are performed at B3LYP/6-311++G** level of theory in the gas-phase. The obtained results indicate that the most preferred sites for donating electron in a reaction with radical or oxidizing molecule are associated mostly with π electrons above and below the aromatic part of the α-tocopherol chromanol ring. The most reactive sites for accepting electrons are associated with the leaving H(9) atom in the extension of the phenolic OH bond on the α-tocopherol chromanol ring plane, in the place where the formation of H-bond of the precursor complex between approaching reactive oxygen radical and phenolic OH group of α-tocopherol could be expected. The separated reactive sites in α-tocopherol suggest that the proton and electron, along with the hydrogen atom transfer (HAT) process, could also be transferred to different proton and electron acceptors as in bidirectional proton coupled electron transfer (PCET) reactions. The results presented in this paper suggest that large charge redistribution and significant π-π interactions may be expected in antioxidant reactions of α-tocopherol.

DFT insights into the structure, reactivity and radical scavenging activity of cycloartocarpesin

“…Fukui function f [ 54 ] is a DFT based reactivity descriptor which has been found to be successful in highlighting reactive sites of molecules. [ 55–57 ] It is defined as the partial derivative of ρ ( r ) (electron density) with respect to N (total number of electrons of the system) at a constant external potential υ ( r ): Moreover, f − ( r ) (the Fukui function for electrophilic attack) and f + ( r ) (for nucleophilic attack) have further been successfully proposed by Yang and Mortier [ 58 ] because the derivative of ρ ( r ) with respect to N is discontinuous. The values of f − ( r ) and f + ( r ) condensed to the k th atom of CAP were calculated (and plotted) from Equations and , based on the finite‐difference approximations.…”

“…The average local ionization energy Ī(r) is a local reactivity descriptor used in analyzing sites suitable for electrophilic or free radical attacks when some degree of charge transfer is involved. [ 56,59 ] ALIE is linked to the electron donor Fukui function f − ( r ) and is interpreted as the average energy necessary to remove an electron from the point r in the space around a molecular system. Its lowest values correspond to the regions with the greatest probabilities of having the least tightly‐held electrons, which are sites favorable for donating electrons.…”

Theoretical Insights into the Switching Off/On of 1O2 Photosensitization in Chemicontrolled Photodynamic Therapy

“…As tudy of the local reactivity of a-tocopherol has recently provided evidence that the phenolic OH bond of the a-tocopherol chromanolr ing should be the most reactive site for acceptinge lectrons in reactions with oxidizingm olecules,f ollowed by leaving of the hydrogen atom, whereas the preferred sites for donating electrons are associated with p electrons of the aromatic part of the a-tocopherol chromanol ring. [40] Either the OH group or the aromatic ring can be reactive sites for the first step. Indeed, as reported in the literature for other phenolic compounds, the oxidation reaction with 1 O 2 provides a1 ,4cycloaddition through the formation of endoperoxide.…”

4-[(4-acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid, a newly synthesized amide with hydrophilic and hydrophobic segments: Spectroscopic characterization and investigation of its reactive properties

“…The assignments of the calculated frequencies were realized using Gaussview 29 and GAR2PED 30 software. The Jaguar 9.0 program 31 was used for the DFT calculations and the Desmond program [32][33][34] was used for the MD simulations, both as implemented in the Schrödinger Materials Science Suite 2015-4. The B3LYP exchange-correlation functional 35 was used for the DFT calculations by the Jaguar program, with 6-311++G(d,p), 6-31+G(d,p) and 6-311G(d,p) basis sets for the calculations of the average local ionization energies (ALIE), Fukui functions and bond dissociation energies (BDEs), respectively.…”