title: Electrophilic reactivity of tetrabromorhodamine 123 is bromine induced: convergent interpretation through complementary molecular descriptors.
abstract: Nucleophilic addition of water and of methanol to 3,6-diamino-2,4,5,7-tetrabromo-9-[2-(methoxycarbonyl) phenyl]-9H-xanthen-9-ylium, 4BrR123, yields respectively 2-(3,6-diamino-2,4,5,7-tetrabromo-9-hydroxy-9H-xanthen-9-yl)xanthyl benzoate, HO4BrR123 and 2-(3,6-diamino-2,4,5,7-tetrabromo-9-methoxy-9H-xanthen-9-yl)xanthyl benzoate, MeO4BrR123. The novel experimental results are addressed theoretically. The linear free energy relationship, LFER, second-order perturbation theory analysis of the natural bond orbital, NBO, and quantum theory of atoms in molecules, QTAIM, lead to the same conclusion: the electron-withdrawing effect of bonded Br atoms in 4BrR123 extremely enhances the molecular electrophilicity, as compared to 3,6-diamino-9-[2-(methoxycarbonyl) phenyl]-9H-xanthen-9-ylium, R123. The reactivity of these diaminoxanthylium cations is discussed in the context of local and global softness in extended conjugated systems.
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Universidade Técnica de Lisboa, Portugal. jose.bracons.ferreira@ist.utl.pt
authors.forename: José A B
authors.initials: JA
authors.lastname: Ferreira
authors.forename: Antonio
authors.initials: A
authors.lastname: Sánchez-Coronilla
authors.forename: Denisio M
authors.initials: DM
authors.lastname: Togashi
authors.forename: Humberto
authors.initials: H
authors.lastname: Ferreira
authors.forename: José R
authors.initials: JR
authors.lastname: Ascenso
authors.forename: Sílvia M B
authors.initials: SM
authors.lastname: Costa
mesh_terms: D001966:Bromine / Q000737:chemistry*; D004583:Electrons; D057927:Hydrophobic and Hydrophilic Interactions; D000432:Methanol / Q000737:chemistry; D015394:Molecular Structure; D011789:Quantum Theory; D012235:Rhodamines / Q000138:chemical synthesis / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D012235:Rhodamines; D014867:Water; C060140:tetrabromorhodamine 123; D001966:Bromine; D000432:Methanol