Nature of electrogenerated intermediates in nitro-substituted nor-β-lapachones: the structure of radical species during successive electron transfer in multiredox centers.
Electrochemical, spectroelectrochemical, and theoretical studies of the reduction reactions in nor-β-lapachone derivatives including a nitro redox center showed that reduction of the compounds involves the formation of several radical intermediates, including a biradical dianion resultant from the separate reduction of the quinone and nitro groups in the molecules. Theoretical descriptions of the corresponding Fukui functions f(αα)⁺ and f(ββ)⁺(r) and LUMO densities considering finite differences and frozen core approximations for describing the changes in electron and spin densities of the system allowed us to confirm these results. A description of the potential relationship with the obtained results and biological activity selectivity indexes suggests that both the formation of stable biradical dianion species and the stability of the semiquinone intermediates during further reduction are determining factors in the description of their biological activity.
Centro de Investigación y Desarrollo Tecnológico en Electroquímica , S.C., Parque Tecnológico Querétaro Sanfandila, 76703 Pedro Escobedo, Querétaro Mexico.
Georgina
G
Armendáriz-Vidales
Lindsay S
LS
Hernández-Muñoz
Felipe J
FJ
González
Antonio A
AA
de Souza
Fabiane C
FC
de Abreu
Guilherme A M
GA
Jardim
Eufrânio N
EN
da Silva
Marilia O F
MO
Goulart
Carlos
C
Frontana
D000838:Anions / Q000737:chemistry*; D001572:Benzofurans / Q000737:chemistry*; D016227:Benzoquinones / Q000737:chemistry*; D004563:Electrochemistry; D005609:Free Radicals / Q000737:chemistry*; D009285:Naphthoquinones / Q000737:chemistry*; D009574:Nitro Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D011789:Quantum Theory
D000838:Anions; D001572:Benzofurans; D016227:Benzoquinones; D005609:Free Radicals; D009285:Naphthoquinones; D009574:Nitro Compounds; C574726:nor-beta-lapachone; C025232:semiquinone radicals