title: Site-Specific Description of the Enhanced Recognition Between Electrogenerated Nitrobenzene Anions and Dihomooxacalix[4]arene Bidentate Ureas.
abstract: Electron transfer controlled hydrogen bonding was studied for a series of nitrobenzene derivative radical anions, working as large guest anions, and substituted ureas, including dihomooxacalix[4]arene bidentate urea derivatives, in order to estimate binding constants (Kb) for the hydrogen-bonding process. Results showed enhanced Kb values for the interaction with phenyl-substituted bidentate urea, which is significantly larger than for the remaining compounds, e.g., in the case of 4-methoxynitrobenzene a 28-fold larger Kb value was obtained for the urea bearing a phenyl (Kb ∼ 6888) vs tert-butyl (Kb ∼ 247) moieties. The respective nucleophilic and electrophilic characters of the participant anion radical and urea hosts were parametrized with global and local electrodonating (ω(-)) and electroaccepting (ω(+)) powers, derived from DFT calculations. ω(-) data were useful for describing trends in structure–activity relationships when comparing nitrobenzene radical anions. However, ω(+) for the host urea structures lead to unreliable explanations of the experimental data. For the latter case, local descriptors ωk(+)(r) were estimated for the atoms within the urea region in the hosts [∑kωk(+)(r)]. By compiling all the theoretical and experimental data, a Kb-predictive contour plot was built considering ω(-) for the studied anion radicals and ∑kωk(+)(r) which affords good estimations.
authors.affiliation: †Centro de Investigación y Desarrollo Tecnológico en Electroquímica, Parque Tecnológico Querétaro Sanfandila, 76703 Sanfandila, Pedro Escobedo, Querétaro, Mexico.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Martínez-González
authors.affiliation: †Centro de Investigación y Desarrollo Tecnológico en Electroquímica, Parque Tecnológico Querétaro Sanfandila, 76703 Sanfandila, Pedro Escobedo, Querétaro, Mexico.
authors.forename: Georgina
authors.initials: G
authors.lastname: Armendáriz-Vidales
authors.affiliation: ‡Centro de Química Estrutural, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: José R
authors.initials: JR
authors.lastname: Ascenso
authors.affiliation: §Centro de Química Estrutural, Faculdade de Ciências da Universidade de Lisboa, Edifício C8, 1749-016 Lisboa, Portugal.
authors.forename: Paula M
authors.initials: PM
authors.lastname: Marcos
authors.affiliation: †Centro de Investigación y Desarrollo Tecnológico en Electroquímica, Parque Tecnológico Querétaro Sanfandila, 76703 Sanfandila, Pedro Escobedo, Querétaro, Mexico.
authors.forename: Carlos
authors.initials: C
authors.lastname: Frontana
mesh_terms: D000838:Anions / Q000737:chemistry; D047250:Calixarenes / Q000737:chemistry*; D055664:Electrochemical Techniques; D004579:Electron Transport; D005609:Free Radicals / Q000737:chemistry; D006860:Hydrogen Bonding; D015394:Molecular Structure; D009578:Nitrobenzenes / Q000737:chemistry*; D014508:Urea / Q000737:chemistry*
chemical_list: D000838:Anions; D005609:Free Radicals; D009578:Nitrobenzenes; C580837:dihomooxacalix(4)arene; D047250:Calixarenes; D014508:Urea; C036077:nitrobenzene