Observation of Both Jahn−Teller Distorted Forms (b1g and b2g) of the Cyclooctatetraene Anion Radical in a 1,2-Disubstituted System

Autor:	Yong Seol Kim, Cheryl D. Stevenson and
Rok vydání:	2000
Předmět:	Chemistry Jahn–Teller effect General Chemistry Ring (chemistry) Photochemistry Biochemistry Catalysis law.invention Bond length Crystallography Cyclooctatetraene chemistry.chemical_compound Colloid and Surface Chemistry Molecular geometry law Molecule Electron paramagnetic resonance Ground state
Zdroj:	Journal of the American Chemical Society. 122:3211-3215
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja9943501
Popis:	The anion radical of cyclooctatetraene (COT) must undergo a Jahn−Teller distortion from its ideal D8h symmetry. Both B3LYP/6-31+G* calculations and EPR observation have shown that the COT moiety in the anion radical of 1,2-dicarbo-tert-butoxycyclooctatetraene exists in a pair of degenerate D4h alternating bond angle conformations (a b1g distortion). The rapid (k = 3 × 107 s-1) interconversion between the two identical conformations leads to specifically predicted line width alternation effects in the EPR spectrum. The COT ring system in the 1,2-dicarbomethoxycyclooctatetraene anion radical [(CH3OOC)2COT-•], on the other hand, has a ground state with alternating bond lengths. Since this b2g distorted (COT-•) system has a plane of symmetry that can be drawn through the molecule and between the two substituents, no line width alternation effects can take place. However, in this system, the B3LYP/6-31+G* calculations predict an energy difference between the b1g and b2g distorted COT-• ring systems of less tha...
Databáze:	OpenAIRE
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