Related Experiment Video
Updated: May 20, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Donor-substituted octacyano[4]dendralenes: investigation of π-electron delocalization in their radical ions
Benjamin Breiten1, Markus Jordan, Daisuke Taura
1Laboratory of Organic Chemistry, ETH Zurich, Hönggerberg, HCI, CH-8093 Zurich, Switzerland.
Abstract:
Symmetrically and unsymmetrically electron-donor-substituted octacyano[4]dendralenes were synthesized and their opto-electronic properties investigated by UV/vis spectroscopy, electrochemical measurements (cyclic voltammetry (CV) and rotating disk voltammetry (RDV)), and electron paramagnetic resonance (EPR) spectroscopy. These nonplanar push-pull chromophores are potent electron acceptors, featuring potentials for first reversible electron uptake around at -0.1 V (vs Fc(+)/Fc, in CH2Cl2 + 0.1 M n-Bu4NPF6) and, in one case, a remarkably small HOMO-LUMO gap (ΔE = 0.68 V). EPR measurements gave well-resolved spectra after one-electron reduction of the octacyano[4]dendralenes, whereas the one-electron oxidized species could not be detected in all cases. Investigations of the radical anions of related donor-substituted 1,1,4,4-tetracyanobuta-1,3-diene derivatives revealed electron localization at one 1,1-dicyanovinyl (DCV) moiety, in contrast to predictions by density functional theory (DFT) calculations. The particular factors leading to the charge distribution in the electron-accepting domains of the tetracyano and octacyano chromophores are discussed.
Related Concept Videos
Radicals: Electronic Structure and Geometry
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Aromatic Hydrocarbon Anions: Structural Overview
Due to the absence of continuous overlap of p...
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
Radical Reactivity: Steric Effects
Along with electronic factors, steric factors also account...
π Molecular Orbitals of the Allyl Radical
The allyl systems have identical molecular orbitals but differ in the number of π electrons.
Aromatic Hydrocarbon Cations: Structural Overview
Removing one hydrogen from the intervening CH2 group with both...

