Intramolecular (electron) delocalization between aromatic donors and theirtethered cation-radicals. Application of electrochemical and structural probes

To study the mechanism of electronic transduction along (poly)phenylene cha ins, a series of aromatic donors with general formula D-B-D has been synthe sized [where D = 2,5-dimethoxy-4-methylphenyl donor and B = (poly)phenylene bridge]; and the corresponding cation-radical salts D-B-D+. SbCl6- have be en isolated for X-ray crystallographic analyses. The magnitude of the elect ronic interaction between the D and D+. moieties through the various B brid ges has been measured (i) as the difference between the first and the secon d oxidation potentials of D-B-D donors and (ii) as the structural changes i nduced in neutral D by the presence of the tethered D+. group in D-B-D+. ca tion-radicals. The intramolecular interaction of D and D+. groups was found to occur via pi -conjugation of the bridging (poly)phenylene group. As suc h, the electronic interaction is highly dependent on the planarity of the ( poly)phenylene bridge, and can be either inhibited or promoted by the delib erate modifications of the molecular conformation. Crystal structures of co mpounds A, B, B+.+.,1, 1(+.), 2,2(+.), 3(+.), 8 and 9(+.) are reported.