Control of Electron Transfer Processes in Multidimensional Arylamine-Based Mixed-Valence Compounds by Molecular Backbone Design

Abstract

Four trigonal topology compounds with three diarylamines redox centers and dibenzofulvene as core bridge have been synthesized. Their radical cations exhibit appealing intramolecular electron transfer pathways between three redox centers, depending on their position on the core bridge. By changing such positions (on either 2,7-or 3,6-), and the length of the bridge, the control of the intramolecular electron transfer pathways was achieved through the electron self-exchange route. These processes were investigated by absorption spectroscopy, electron paramagnetic resonance spectroscopy, and (time-dependent) density functional theory calculations. Hole mobility measurements were carried out as well, to correlate the intramolecular electron transfer with the hole-transporting ability for possible applications in optoelectronic devices.

Synthesis and Investigation of Electro-Optical Properties of H-Shape Dibenzofulvene Derivatives

“…Indeed, this energy transition is absent in the absorption spectra of H2 and H5 . As we reported previously [ 18 ], in the latter systems, a larger coupling between the arylamino units with the DBF occurs, which enhances the delocalization of the molecular orbitals on the DBF as well as on the diphenylamine substituents. As a consequence, the DBF π−π* transition is not observed in these systems, but rather a mixed π−π*-CT transition around 265 nm, also involving the diphenylamines.…”

“…In all compounds, the low-energy electron transition can be assigned to the amino-to-bridge charge-transfer character (NB-CT). The results show that the amino substituents contribute differently to the NB-CT depending on their anchoring position on the DBF [ 17 , 18 ]. In fact, in the systems H1 , H3 , H4 and H6 , the redox centers transfer only partially the charge to the bridge, unlike for the H2 and H5 systems where a greater contribution of the amino groups to the charge transfer to the bridge is observed ( Figures S2–S4 ).…”

Correlating the chemical structure and charge transport ability of dibenzofulvene-based hole transporting materials for stable perovskite solar cells

“…Compounds T2N3 , TN3 , mT2N3 and mTN3 were synthesized according to a previously reported procedure. 11…”

“…Thus, the HOMO levels of the four materials, including spiro, were estimated using cyclic voltammetry. 11 The calculated HOMO energy levels together with the lowest unoccupied molecular orbital (LUMO) values are reported in Fig. 2 (colored box).…”

“…We have already reported the synthesis, electrochemical characterization and study of the intramolecular electron transfer of these materials as a function of the position of the arylamino moieties on the DBF core. 11 This family of materials presented several advantages such as a straightforward synthesis, a high conversion yield, and hence potentially low-cost, and an excellent radical cation stability. However, in our previous work, 11 we considered mainly molecules in solution.…”