Intramolecular (electron) delocalization between aromatic donors and their tethered cation–radicals. Application of electrochemical and structural probes†
作者:Duoli Sun、Sergey V. Lindeman、Rajendra Rathore、Jay K. Kochi
DOI:10.1039/b103139m
日期:——
To study the mechanism of electronic transduction along (poly)phenylene chains, a series of aromatic donors with general formula DâBâD has been synthesized [where DÂ =Â 2,5-dimethoxy-4-methylphenyl donor and BÂ =Â (poly)phenylene bridge]; and the corresponding cationâradical salts DâBâD+Ë SbCl6â have been isolated for X-ray crystallographic analyses. The magnitude of the electronic interaction between the D and D+Ë moieties through the various B bridges has been measured (i) as the difference between the first and the second oxidation potentials of DâBâD donors and (ii) as the structural changes induced in neutral D by the presence of the tethered D+Ë group in DâBâD+Ë cationâradicals.
The intramolecular interaction of D and D+Ë groups was found to occur via
Ï-conjugation of the bridging (poly)phenylene group. As such, the electronic interaction is highly dependent on the planarity of the (poly)phenylene bridge, and can be either inhibited or promoted by the deliberate modifications of the molecular conformation. Crystal structures of compounds A, B, B+Ë+Ë, 1, 1+Ë, 2, 2+Ë, 3+Ë, 8 and 9+Ë are reported.
为了研究电子转导在(聚)苯链中的机制,合成了一系列具有一般式D–B–D的芳香供体[其中D=2,5-二甲氧基-4-甲基苯基供体,B=(聚)苯桥];并且相应的阳离子-自由基盐D–B–D+·SbCl6−已被分离以进行X射线晶体学分析。通过不同的B桥测量了D与D+·部分之间的电子相互作用强度,(i) 作为D–B–D供体的第一和第二氧化电位之间的差异,以及(ii) 作为中性D中因存在连接的D+·团而引起的结构变化。在分子内D和D+·团的相互作用被发现通过桥接的(聚)苯基团的π-共轭发生。因此,电子相互作用高度依赖于(聚)苯桥的平面性,并且可以通过对分子构象的刻意修改来抑制或促进。报告了化合物A、B、B+·、1、1+·、2、2+·、3+·、8和9+·的晶体结构。