Cyclic In-Plane Electron Delocalization (σ-Bishomoaromaticity) in 4N/5e Radical Anions and 4N/6e DianionsGeneration, Structures, Properties, Ion-Pairing, and Calculations
| Autor: | Lorenz Liesum, Birgit Grossmann, Markus Vögtle, Kai Exner, Georg Gescheidt, Horst Prinzbach, Oliver Cullmann, Rainer Bachmann, and Arthur Schweiger, Jürgen Heinze |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 122:10650-10660 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja0014943 |
| Popis: | Cyclic delocalization of five and six electrons, respectively, in the plane of four N centers was explored by one-/two-electron reduction of more or less rigid, parallel bisdiazenes (1−7), with NN/NN distances (dππ) ranging from ∼2.8 to 5.0 A, interorbital angles (p,p; ω) from ∼l75° to 90°, and with more or less kinetic protection. For the “proximate” substrates 1−5 (dππ ≈ 2.8−3.2 A, ω ≈ 175−156°), short contact with alkali metals (Li, Na, K, Cs) generates turquoise to deeply green radical anions (λmax(DME) ≈ 700−900 nm). The character of these radical anions as cyclically in-plane delocalized bishomoconjugated 4N/5e species with a high concentration of spin density between the NN units is established by extensive UV/vis, electrochemical, and EPR measurements (CW, pulsed) at temperatures down to 8 K, and by DFT calculations (B3LYP/6-31G*). After longer exposure to the metals, the three most persistent 4N/5e radical anions (M+1•-, M+2•-, M+5•-) are further reduced to the red dianions (2M+12-, 2M+22-, 2M+52... |
| Databáze: | OpenAIRE |
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