title: From Blue to Green: Fine-Tuning of Photoluminescence and Electrochemiluminescence in Bifunctional Organic Dyes.
abstract: We describe the synthesis, computational analysis, photophysics, electrochemistry and electrochemiluminescence (ECL) of a series of compounds formed of two triphenylamines linked by a fluorene or spirobifluorene bridge. The phenylamine moieties were modified at the para-position of the two external rings by electron-withdrawing or electron-donating substituents. These modifications allowed for fine-tuning of the photoluminescence (PL) and ECL emission from blue to green, with an overall wavelength span of 73 (PL) and 67 (ECL) nm, respectively. For all compounds, we observed a very high PL quantum yield (79-89%) and formation of stable radical ions. The ECL properties were investigated by direct annihilation of the electrogenerated radical anion and radical cation. The radical-ion annihilation process is very efficient and causes an intense greenish-blue ECL emission, easily observable even by naked eye, with quantum yield higher than the standard 9,10-diphenylanthracene. The ECL spectra show one single band that almost matches the PL band. Because the energy of the annihilation reaction is higher than that required to form the singlet excited state, the S-route is considered the favored pathway followed by the ECL process in these molecules. All these features point to this type of molecular system as promising for ECL applications.
authors.affiliation: Institute of Molecular Science and Technologies (ISTM), National Research Council (CNR), PST-CNR , via Fantoli 16/15, 20138 Milano, Italy.|Institute of Molecular Science and Technologies (ISTM), National Research Council (CNR), and INSTM, c/o Department of Chemistry, University of Milano , via Golgi 19, 20133 Milano, Italy.
authors.forename: Fabio
authors.identifier: 0000-0003-4045-2653
authors.initials: F
authors.lastname: Rizzo
authors.affiliation: Department of Chemistry, University of Padova , via Marzolo 1, 35131 Padova, Italy.
authors.forename: Federico
authors.identifier: 0000-0003-4638-396X
authors.initials: F
authors.lastname: Polo
authors.affiliation: Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE), National Research Council (CNR), c/o Department of Chemistry, University of Padova , via Marzolo 1, 35131 Padova, Italy.
authors.forename: Gregorio
authors.initials: G
authors.lastname: Bottaro
authors.affiliation: Institute of Molecular Science and Technologies (ISTM), National Research Council (CNR), c/o Department of Chemistry, University of Perugia , via Elce di Sotto 8, 06123 Perugia, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Fantacci
authors.affiliation: Department of Chemistry, University of Padova , via Marzolo 1, 35131 Padova, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Antonello
authors.affiliation: Department of Chemistry, University of Padova , via Marzolo 1, 35131 Padova, Italy.|Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE), National Research Council (CNR), c/o Department of Chemistry, University of Padova , via Marzolo 1, 35131 Padova, Italy.
authors.forename: Lidia
authors.initials: L
authors.lastname: Armelao
authors.affiliation: Institute of Molecular Science and Technologies (ISTM), National Research Council (CNR), and INSTM, c/o Department of Chemistry, University of Milano , via Golgi 19, 20133 Milano, Italy.
authors.forename: Silvio
authors.initials: S
authors.lastname: Quici
authors.affiliation: Department of Chemistry, University of Padova , via Marzolo 1, 35131 Padova, Italy.
authors.forename: Flavio
authors.initials: F
authors.lastname: Maran