Linear Oligoarylamines: Electrochemical, EPR, and Computational Studies of Their Oxidative States

Abstract

A series of straight-chain oligoarylamines were synthesized and examined by electrochemical, spectroelectrochemical, electron paramagnetic resonance techniques, and density functional theory (DFT) calculation. Depending on their electrochemical characteristics, these oligoarylamines were classified into two groups: one containing an odd number and the other an even number of redox centers. In the systems with odd redox centers (N1, N3, and N5), each oxidation was associated with the loss of one electron. As for the systems with even redox centers (N2, N4, and N6), oxidation occurred by taking N2 as a unit. Absorption spectra of linear oligoarylamines at various oxidative states were obtained to investigate their charge transfer behaviors. Moreover, DFT-computed isotropic hyperfine coupling constants and spin density were in accordance with the EPR experiment, and gave a close examination of oligoarylamines at charged states.

Tricarbonylrhenium(I) Complexes of Dinucleating Redox-Active Pincer Ligands

“…The former setup with larger K com suggests that the one-electron oxidized species 1 + would be near the Robin–Day Class II/Class III border ( K com ≥ 10 6 , Class III) for a mixed valence compound, while the latter, in electrolyte-containing DMF, suggests 1 + to be a Class II mixed valence compound. Similar observations have been made for purely organic N , N , N , N -(tetra­aryl)­ben­zidene derivatives, which have varying Δ E ’s between 215 and 300 mV ( K com between 10 3 and 10 4 ) in electrolyte-containing CH 2 Cl 2 . − Noteworthy, these organic (tetra­aryl)­ben­zidine cation radicals are fully delocalized (Class III) in CH 2 Cl 2 without electrolyte, based on spectroscopic measurements and theoretical studies. − For 2 , the first oxidation potential is ca. 200 mV more positive than in 1 , showing that this diamine is less electron-rich than that in 1 .…”

“…In each case, new bands are found in the NIR region that are assigned as charge resonance for 1 + and as intervalence charge transfer (IVCT) for 2 + . The charge resonance assignment for bands in 1 + is aligned with voluminous literature on Robin–Day Class III radical cations of benzidene − variants (like the aforementioned N , N ,­ N ′ N ′-tetra­aryl­ben­zidene derivatives). The assignment of an IVCT band for 2 + is based on the EPR data that suggests Class II behavior.…”

meta‐ and para‐Phenylenediamine‐Fused Porphyrin Dimers: Synthesis and Magnetic Interactions of Their Dication Diradicals

“…Accordingly, the electrochemical HOMO–LUMO gaps are 2.02 V for 9 m and 1.72 V for 9 p . The observed smaller gap of 9 p can be ascribed to the presence of the para ‐phenylenediamine segment . The fused dimers 10 m and 10 p exhibited highly split multistage oxidation behaviors in reversible ways above 0.11 V. These properties supported effective electronic couplings between two diarylamine‐fused porphyrin units.…”

Efficiency-limiting processes in cyclopentadithiophene-bridged donor-acceptor-type dyes for solid-state dye-sensitized solar cells

“…1 for chemical structures), which use CDT and TPA-based building blocks as bridging and donor units, respectively. The TPA donor-units used here were chosen, as they exhibit certain structural attributes, which are expected to have an impact on the photophysics and device performance: indolo[3,2,1-jk]carbazole (1) provides extended π-conjugation and planarity, the triangulene type triarylamine (2) shows reduced aggregation through steric hindrance of the methylene groups, and the dendritic structure (3) is a strong donor-unit with a half wave potential (E 1/2 ) of +0.55 V. 18 Steady-state spectroscopy techniques were used to study the optical properties of these dyes, and broadband transient absorption spectroscopy (TAS) was employed to investigate the excited-state dynamics of transient states such as excitons, charge-transfer states, and charges in device-like samples. The combination of well-selected dye structures and advanced spectroscopy techniques allows us to understand the efficiency-limiting processes in this class of dyes and derive structure-property relations for a better-guided material design.…”