Formation of Highly Stabilized Intramolecular Dimer Radical Cation and π-Complex of [3_n]Cyclophanes (n = 3, 5, 6) during Pulse Radiolysis

Abstract

Formation of radical cation and charge-transfer complex of [3n]cyclophanes (n = 3, 5, 6) was investigated by transient absorption spectroscopy during pulse radiolysis. Radical cations of [3n]cyclophanes showed the charge resonance band around 700 nm which exhibited a blue-shift as the number of trimethylene bridges increased, indicating formation of highly stabilized intramolecular dimer radical cation of [3n]cyclophanes. The absorption peak of the charge-transfer complex with chlorine atom also showed the shift in accord with the oxidation potential of [3n]cyclophanes.

Delocalization and Migration of Excitation Energy and Charge in Supramolecular Systems

“…The estimated β value is smaller than that estimated for the intramolecular dimer radical cation of cyclophanes (0.83 Å − 1 ). 80,81 The present result indicates that the negative charge delocalizes in stacked chromophores in a manner similar to the positive charge, indicating that the negative charge is a potentially good carrier in organic assemblies, as is the positive charge.…”

“….12 shows the transient absorption spectra of[3 3 ](1,3,5)CP in 1,2 -dichloroethane during pulse radiolysis 80,81. The spectrum of[3 3 ](1,3,5)CP at 50 ns after the pulse irradiation exhibited sharp and broad peaks at 510 and 730 nm, respectively.…”

Formation of intramolecular dimer radical ions of diphenyl sulfones

“…Intramolecular dimer radical ions are produced through molecular relaxation after neutral molecules are changed into radical ions. Previous reports have investigated the inter-and intra-molecular production of many dimer radical cations [5][6][7][8][9][10][11][12][13] and trimer radical cations 14 in the condensed phase, attributed to the charge resonance (CR) in plural aromatic rings. However, in many cases, dimer radical anions are not observed even if dimer radical cations are formed 8 .…”

Formation of the Charge‐Localized Dimer Radical Cation of 2‐Ethyl‐9,10‐dimethoxyanthracene in Solution Phase

“…[1,2] In this regard, aromatich ydrocarbons that can easily undergo one-electrono xidation/reduction have been widely recognized as good model systems for studying chargel ocalization/delocalization in their radicali ons as well as charge stabilization through charge-resonancedimerization. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] Experimentally,c harged elocalization over multiple units has been identified with characteristic absorption bands in the near-IR region due to the spatialo verlap of p-orbitals. [4,6,14,16] Such key spectroscopic signatures have been used for studying the kinetics of formation,t ransportation, and annihilation of chargec arriers,s uch as radicali ons in organic andb iomolecular systems.…”

“…[18] In particular,M ajimaand co-workersreported that both radical cations and anionso f[ 3 n ]c yclophane generated by pulse radiolysis are stabilized by the charge-resonance interactions betweenb enzene rings andt hat the positive chargeo f multilayered cyclophanes is also stabilized by the aromatic charge-resonancei nteractions among p-stacked benzene ring moieties. [6,9,17] In addition, the foldingk ineticso faDNAs trand were measured by monitoring the charger esonance (charge delocalization) band on the micro-to millisecond time scale. [10][11][12] Spectroscopice videncef or the existence of charge-localized states, in which the extra chargei sl ocalized in as ingle unit instead of being spreadi nm ultiple units, in symmetric molecular systemsa lso has been presented.…”