Optical Spectra of Protected Diamine 10-Bond-Bridged Intervalence Radical Cations Related to N,N,N‘N‘-Tetraalkylbenzidine

Abstract

The optical absorption spectra of the delocalized intervalence radical cations of seven o,o'-linked benzidine derivatives that have the nitrogens protected as 9-(9-aza-bicyclo[3.3.1]nonan-3-one) derivatives are discussed and compared with that of the p-phenylene radical cation. The linking units are CH2, CH2CH2, NMe, S, SO2, and C=O, and we also studied H,H (the unlinked benzidine). The lowest-energy absorption band is assigned as the transition from the antibonding combination of symmetrical N and aromatic orbitals to the antibonding combination of the antisymmetric N and aromatic orbitals using TD-DFT calculations, and a good correlation between the observed transition energies and those calculated using the simple Koopmans theorem-based "neutral in-cation geometry" calculations on the UB3LYP/6-31G* structures is found. The use of the two-state model that equates the electronic interaction through the bridge between the amino groups with half of the lowest transition energy is seriously incorrect for these and other delocalized intervalence compounds. The problem of extracting the electronic interactions that actually are involved from calculated transition energies is discussed.

Resonance Raman spectroscopic study of solvent-dependent coexistence of localized and delocalized dinitroaromatic radical anions

“…15 The intense absorption bands of the anions experimentally observed in the near IR and visible regions have been assigned in previous work using both TD-DFT and Koopman's based calculations. 8,[16][17][18] In all three radical anions, the low energy band with an electronic origin occurring just above 5000 cm −1 (2000 nm) was assigned as a B 1 transition, SOMO ¡ LUMO. The high energy band, with an electronic origin occurring near 18000 cm −1 (555 nm) was assigned as an A 1 transition, HOMO ¡ SOMO.…”

“…Transitions from both filled and virtual orbitals are numbered as their energy separation from the SOMO increases. In Koopmansbased calculations, 8,[16][17][18] transitions are assigned using neutral at the radical anion geometry for the type A transitions, and dianion at the radical anion geometry for the type B transitions. Koopmansbased calculations often produce values that are closer to the observed transition energies than TD-DFT calculations, despite the fact that Koopmans-based calculations ignore configuration interaction.…”

Organische gemischtvalente Verbindungen: ein Spielplatz für Elektronen und Löcher

“…[ + haben Extinktionskoeffizienten von mindestens e > 40 000 cm À1 bei vergleichbaren Energien). [221] Die Entkopplung bei 124 + kommt hauptsächlich von einer Verdrillung um die C-O-Bindung zwischen dem neutralen Dialkylanilin-Teil und den freien Elektronenpaaren am Sauerstoff. Man erhält durch eine Mulliken-Hush-Analyse der optischen Daten zusammen mit AM1-berechneten Dipolmomenten eine elektronische Kopplung von V = 810 cm À1 in Dichlormethan.…”

Transition‐Metal‐Free Synthesis of Carbazoles and Indoles by an SNAr‐Based “Aromatic Metamorphosis” of Thiaarenes

“…[9] From similar precursors,photoinduced cyclization occurs by ar adical process to yield carbazoles. [15] This conventional process is useful as the first step for the aromatic metamorphosis. [11] Regardless of these elegant protocols,t here still remains ample room to develop novel strategies to prepare carbazoles without recourse to transition-metal catalysts.…”

“…[15] This conventional process is useful as the first step for the aromatic metamorphosis. [15] This conventional process is useful as the first step for the aromatic metamorphosis.…”