EPR, ENDOR and TRIPLE resonance characterization of three paramagnetic redox stages of 5-methylene-5H-dibenzo [a,d]cycloheptene
作者:M. Luisa、T. M. B. Franco、M. Celina、R. L. R. Lazana
DOI:10.1039/ft9949003273
日期:——
Radical anions and radical trianions derived from 5-methylene-5H-dibenzo [a,d]cycloheptene 1, 10-deuterio-5-methylene-5H-dibenzo[a,d] cycloheptene 1d and 5-dideuteriomethylene-5-H-dibenzo[a,d]cycloheptene 1d2 by reduction with lithium, sodium, potassium and caesium in ethereal solvents have been studied by EPR, ENDOR and TRIPLE resonance spectroscopy. The spin and charge distribution in 1˙– and 1˙3– are discussed both in terms of HMO–McLachlan and INDO calculations. The energies of the lowest unoccupied molecular orbital (LUMO) and of the next lowest unoccupied molecular orbital (NLUMO) are influenced differently by the strong interaction of the supercharged radical trianion with the counter-cations. A change in the orbital sequence of LUMO and NLUMO was predicted theoretically for the radical trianion relative to that found for the radical anion, in accordance with the experimental results.The radical cations 1˙+, 1d˙+ and 1d2˙+ obtained via oxidation by AICI3 in dichloromethane solution were also studied by EPR, ENDOR and TRIPLE resonance spectroscopy. The experimental results were also interpreted in terms of HMO–McLachlan and INDO methods.
通过对5-亚甲基-5H-二苯并[a,d]环庚烯1、10-氘代-5-亚甲基-5H-二苯并[a,d]环庚烯1d和5-二氘代亚甲基-5H-二苯并[a,d]环庚烯1d2在乙醚溶剂中用锂、钠、钾和铯还原得到的自由基阴离子和自由基三阴离子进行EPR、ENDOR和TRIPLE共振光谱研究。讨论了1•–和1•3–中的自旋和电荷分布,涉及HMO-McLachlan和INDO计算。最低未占据分子轨道(LUMO)和次低未占据分子轨道(NLUMO)的能量受超荷自由基三阴离子与反荷阳离子之间的强相互作用影响不同。理论预测了相对于自由基阴离子,自由基三阴离子的LUMO和NLUMO轨道顺序的变化,这与实验结果一致。通过在二氯甲烷溶液中用AICI3氧化获得的自由基阳离子1•+、1d•+和1d2•+也通过EPR、ENDOR和TRIPLE共振光谱进行了研究。实验结果也通过HMO-McLachlan和INDO方法进行了解释。