Radical Ions of Crownophanes Derived from Tetraphenylethene. Solution Structures and Ion-Pairing Phenomena

Abstract

Radical anions and radical cations of parent tetraphenylethene (1) and its cyclophane derivatives 2−8 were generated by chemical methods. These paramagnetic species were characterized by their ESR and simultaneously recorded optical spectra. The hyperfine coupling constants were substantiated by ENDOR and their signs by general TRIPLE spectroscopy. The structures of the radical ions were established with the help of quantum chemical calculations. The electron distribution in the phane radical ions is closely related to that found for 1^•-/1^•+. In the radical anions no specific complexation of alkali-metal counterions, K⁺ and Li⁺, by the crown-ether moieties could be observed. When the radical cations were generated by oxidation with Tl^III trifluoroacetate in 1,1,1,3,3,3-hexafluoropropanol, distinctly different ESR spectra were recorded as with the use of other oxidants. This observation is rationalized by the characteristic solvation properties of 1,1,1,3,3,3-hexafluoropropanol

Synthesis and Electrochemical Properties of Tetrasubstituted Tetraphenylethenes

“…For example, they can undergo photocyclization to the corresponding diphenylphenanthrenes. [1][2][3][4] Upon oxidation tetraphenylethenes easily form radical cations and dications, respectively, [5][6][7] while reduction with alkali metals leads to dianions. Both dianions [8] and dications [5,9] can be characterized by crystallography.…”

Thallium(III) in Organic Synthesis

“…127 TTFA can act as one-electron oxidant, generating cation radicals. Recent compounds that were treated with TTFA with this goal are: i) benzodithiopyridines in trifluoroacetic acid or in dichloromethane; 128,129 ii) crownophanes derived from tetraphenylethene in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFP); 130 iii) anthracene-bridged h 5 -cyclopentadienyl derivatives of rhodium(I) in dichloromethane and HFP; 131 iv) pyrrole derivatives in trifluoroacetic acid; 132,133 v) anthrylmethyl h 5 -cyclopentadienyl derivatives of rhodium(I) and iridium(I) in dichloromethane and HFP; 134 vi) anthryl-substituted b-ketoenolates of rhodium(I) and iridium(I) in dichloromethane and HFP; 135 vii) homobimetallic anthracene-bridged h 5 -cyclopentadienyl derivatives of rhodium(I) and iridium(I) in dichloromethane and HFP; 136 and viii) coronene in HFP. 137…”

Electron‐transfer Reactions of Aromatic Compounds

“…The work demonstrates the efficiency of the 2D exchange FT EPR method in elucidating mechanisms of dynamic processes and determining kinetic parameters, in particular when several such processes occur simultaneously. Radical anions and radical cations of tetraphenylethane and its cyclophane derivatives were generated by chemical methods and characterized by their EPR and simultaneously recorded optical spectra [67]. In radical anions no specific complexation of alkali-metal counterions, K+ and Li+, by the crown-ether moieties could be observed.…”