Efficient Greenish Blue Electrochemiluminescence from Fluorene and Spirobifluorene Derivatives

Abstract

The spectroscopic and electrochemical behavior as well as electrogenerated chemiluminescence (ECL) of a series of donor-π-donor derivatives bearing triphenylamine groups as donor connected to a fluorene, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9'-dimethylfluorene (1), or spirobifluorene core, 2,7-bis-(4-(N,N-diphenylamino)phen-1-yl)-9,9'-spirobifluorene (2) and 2,2',7,7'-tetrakis(4-(N,N-diphenylamino)phen-1-yl)-9,9'-spirobifluorene (3), were investigated. Besides a high photoluminescence (PL) quantum yield in solution (between 81 and 87%), an efficient radical ions annihilation process induces intense greenish blue ECL emission that could be seen with the naked eye. Only the tetrasubstituted spirobifluorene derivative (compound 3) shows weak ECL obtained by a direct annihilation mechanism. Because the energy of the annihilation reaction is higher than the energy required to form the singlet excited state, the S-route could be considered the pathway followed by the ECL process in these molecules. The ECL emissions recorded by direct ion-ion annihilation show two bands compared to the single structureless PL band. The ECL spectra obtained by a coreactant approach using benzoylperoxide as a coreagent show no differences relative to that produced by annihilation, except for an increasing of ECL intensity for all compounds.

Bright Electrogenerated Chemiluminescence of a Bis‐Donor Quadrupolar Spirofluorene Dye and Its Nanoparticles

“…By comparison with the corresponding fluorescence spectra, redshifts were observed in ECL spectra (7 nm for 1 and 3 nm for 4 ). Such redshifts are common in ECL and are caused by the inner filter effect due to the high concentration of chromophores used in ECL experiments . Nonetheless, these results confirmed that the same excited state 1 * were produced by photochemical and electrochemical excitation.…”

“…This demonstrates a diffusion‐controlled process on the Pt surface in this potential window for all three well‐separated anodic steps. The next two reversible anodic one‐electron waves are consistent with oxidation of the central spirofluorene core . However, another hypothesis that cannot be excluded is that the reversible one‐electron oxidation waves are related to oxidation of the thiophene moieties.…”

Synthesis and Characterization of Dibenzo[a,d]cyclohepten‐5‐one Derivatives for Light‐Emitting Diodes

“…During the past decades, great efforts were focused on the development of novel EL materials. [11][12][13][14][15] Organic molecules with conjugated π-electron systems have been extensively studied and demonstrated as ideal materials for applications in OLEDs in recent years. [16][17][18][19][20] Luminescent properties and charge carrier transporting characteristics of a conjugated molecule can be tuned by modification of its molecular structure, which may provide valuable routes to construct new materials with excellent all-round properties.…”

Efficient Luminescence from Fluorene‐ and Spirobifluorene‐Based Lanthanide Complexes upon Near‐Visible Irradiation

“…Fluorene and 9,9′‐spirobifluorene derivatives with tailor‐made optical and redox properties are being actively investigated as organic light‐emitting materials for optoelectronics and in electrogenerated chemiluminescence studies 20–22…”