Triarylamine‐Based Organic Mixed‐Valence Compounds

Synthesis, Structures, and Properties of Neutral and Radical Cationic S,C,C-Bridged Triphenylamines

“…Triarylamine derivatives usually exhibit a trigonal planar geometry, wherein the three aryl rings adopt a propeller-shaped structure. These compounds represent an important class of π-electron donors, and they have been investigated as components for organic semiconductors. , Triarylamines have also attracted significant interest as redox-active units or spin sources in organic mixed-valence systems and in the context of molecular magnetism. , It is therefore hardly surprising that organic chemists have devoted continuous efforts to the development of synthetic routes to various triarylamine radical cations and evaluation of their structures and physicochemical properties . Among the triarylamines that have been reported, some para -substituted triphenylamines form stable radical cations, e.g., the commercially available tris­(4-bromophenyl)­aminium hexachloroantimonate, which is also known as “magic blue” .…”

Connecting Organic Redox‐Active Building Blocks through Mild Noncatalytic C−H Activation

“…[21] Obviously, quantum-chemical calculations gain more and more importance to complement the analysis, as, for example, shown in recent years in representative combined experimental and quantum-chemical (DFT) studies of coupled bistriarylamine radical cations. [22][23][24][25] Quinones, [26][27][28][29][30] triarylamines, [8,[31][32][33] hydrazines, [2,[34][35][36] and nitroaromatic groups [37][38][39] are among the widely used redoxactive units for the construction of organic MV compounds. One-electron reduction (e. g. for systems with two or more quinone or nitroaromatic groups) or one-electron oxidation (e. g. for systems with two or more triarylamines or hydrazines) leads to MV compounds.…”

“…Systems with two or more redox-active organic units that are connected through a bridge that allows electronic coupling between these units were intensively studied. One-electron redox reactions of such molecules lead to mixed-valence (MV) compounds, [2][3][4][5][6][7][8][9] that could be classified with respect to the degree of charge delocalization (Robin-Day classes I-III). [10] Apart from their (potential) applications in materials science, [5] they serve as model systems for a detailed understanding of electron transfer (ET), being of key importance in a number of complex (photoinduced) biophysical processes, often being accompanied by proton transfer or changes in hydrogen bonding.…”

“…[44][45][46][47] Systems with up to six triarylamine units were synthesized, [32,48] and the role of the bridge between the triarylamine units and also of the solvent for the electron transfer pathway thoroughly investigated. [8,[49][50][51][52][53][54] Redox-active guanidines constitute a versatile new class of redox-active organic molecules, consisting of two sub-classes, redox-active urea azines and guanidino-functionalized aromatics (GFA). [55] Figure 1 shows a selection of GFA compounds with benzene core.…”

Optically Induced Charge Transfer in Organic Mixed-Valence Systems: Wave Packet Dynamics and Femtosecond Transient Spectroscopy

“…Mixed-valence (MV) compounds − present model systems for electron transfer (ET) processes. − These molecules consist of two or more redox centers connected by bridge molecules where a charge can be transferred between the redox centers as well as the centers and the bridge, respectively. In case of, e.g., radical cation MV compounds, the latter happens only if bridge redox potentials are low enough to be accessible.…”