Guidi Vanina V, Jin Zhou, Busse Devin, Euler William B, Lucht Brett L
Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, USA.
J Org Chem. 2005 Sep 16;70(19):7737-43. doi: 10.1021/jo051196u.
[graph: see text] The electrochemical, structural, and spectroscopic properties of bis(phosphine imide)s have been investigated. p-Phenylenebis(phosphine imide)s Ar3PNC6H4NPAr3 (1a-d) have two reversible single-electron oxidations. The first oxidation potentials can be varied from -0.05 to 0.15 V (versus SCE) by modification of the substituents on phosphorus (Ar). Electron-donating substituents lower the oxidation potential, while electron-withdrawing substituents increase the oxidation potential. The difference between the first and second oxidation potential (deltaE, 0.41-0.50) and the electronic coupling (Hab, 1.1 eV) are similar for 1a-d. Computational (DFT) and UV-visible-NIR spectroscopic investigations of 1a-d suggest that the first oxidation leads to a delocalized radical cation 1a*+ while the second oxidation leads to a quinonoidal dicationic state 1a2+. The aromatic linker between phosphine imides has also been modified. Upon oxidation, N,N'-4,4'-biphenylene(bis(triphenyl)phosphine imide) (3) forms radical cationic and a dicationic species similar to 1a-d. While deltaE (0.18 V) and Hab (0.63 eV) are smaller, suggesting weaker electronic communication between the two P=N units in the radical cationic state, the presence of NIR absorptions with vibrational fine structure (768, 861, and 983 nm) supports the formation of delocalized radical cation for 3*+.
[图：见正文] 对双（膦酰亚胺）的电化学、结构和光谱性质进行了研究。对亚苯基双（膦酰亚胺）Ar3PNC6H4NPAr3（1a - d）有两个可逆的单电子氧化过程。通过改变磷上的取代基（Ar），首次氧化电位可在 - 0.05至0.15 V（相对于饱和甘汞电极）之间变化。供电子取代基会降低氧化电位，而吸电子取代基会提高氧化电位。对于1a - d，首次和第二次氧化电位之差（ΔE，0.41 - 0.50）以及电子耦合（Hab，1.1 eV）相似。对1a - d的计算（密度泛函理论）和紫外 - 可见 - 近红外光谱研究表明，首次氧化产生离域自由基阳离子1a*⁺，而第二次氧化产生醌型双阳离子态1a²⁺。膦酰亚胺之间的芳族连接基也已被修饰。氧化时，N，N'- 4,4'-联亚苯基（双（三苯基）膦酰亚胺）（3）形成与1a - d类似的自由基阳离子和双阳离子物种。虽然ΔE（0.18 V）和Hab（0.63 eV）较小，表明在自由基阳离子态下两个P = N单元之间的电子通讯较弱，但具有振动精细结构的近红外吸收（768、861和983 nm）的存在支持了3*⁺离域自由基阳离子的形成。
