p-Phenylenevinylene oligomers with application as photoredox catalysts in organic synthesis

Sixteen p-phenylenevinylene oligomers (OPVs) substituted with different electron-donating (ED) and electron-withdrawing (EW) groups were synthesized by the Mizoroki-Heck cross coupling reaction in moderate to good yields (40-95%), and with a totally trans-trans configuration in the vinyl bonds, which is difficult to obtain following common synthetic methodologies. Their structures were stablished by spectroscopic methods (FT-IR, 1H, 13C and Solid-State NMR), elemental analysis, and by mass spectrometry (MALDI-MS). The effect of the molecular structure on the optical properties was studied by UV-vis and fluorescence spectroscopies. The ED and EW groups at the ends of OPVs lead to a bathochromic shift with trends associated to the electronic nature of the substituents, effect that is intensified with the introduction of methoxy groups on the central ring. These groups also influence other properties such as the HOMO-LUMO gaps (E) and the fluorescence quantum yields (f). The most appropriate OPVs were evaluated as photoredox catalysts in synthetic reactions: a) the dehalogenation of vicinal dibromides, b) the aza-Henry reaction and, c) the hydroxylation of aryl boronic acids. Results showed that the OPVs have photoinduced electron transfer (PET) properties, being active in reduction reactions favored by ED-OPVs, and oxidation reactions favored by EW-OPVs. However, these trends could change when species such as amines and reactive oxygen species are present. This work contributes to the understanding of these important compounds and to the developing of new metal-free photoredox catalysts, providing insights about the structural features that polymeric analogs must have in order to get high efficiencies in this application.

• Autores: Estrada Flórez, Sandra Elizabeth
• Tipo de recurso: Doctoral thesis
• Fecha de publicación: 2017
• Institución: Universidad Nacional de Colombia
• Repositorio: Universidad Nacional de Colombia
• Idioma: spa
• OAI Identifier: oai:repositorio.unal.edu.co:unal/62838
• Acceso en línea: https://repositorio.unal.edu.co/handle/unal/62838; http://bdigital.unal.edu.co/62078/
• Palabra clave: 54 Química y ciencias afines / Chemistry; 62 Ingeniería y operaciones afines / Engineering; Phenylenevinylene systems; Mizoroki-Heck reaction; Optoelectronic properties; Photoredox catalysis; Dehalogenation; Hydroxylation; Aza-Henry reaction
• Rights: openAccess
• License: Atribución-NoComercial 4.0 Internacional