Issue 1, 2011

Donor-substituted octacyano[4]dendralenes: a new class of cyano-rich non-planar organic acceptors

Abstract

Double [2+2] cycloaddition/retro-electrocyclisation reactions between tetracyanoethene (TCNE) and various anilino-capped buta-1,3-diynes furnished a series of octacyano[4]dendralene derivatives featuring intense, low-energy intramolecular charge-transfer absorptions. These novel chromophores are strong electron acceptors and undergo facile one-electron reductions at potentials (–0.09 to –0.17 eV vs.Fc+/Fc, in CH2Cl2–0.1 M nBu4NPF6) lower than those reported for the benchmark organic acceptors, such as TCNE (–0.32 eV) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) (–0.25 eV). The electron-accepting power of one octacyano[4]dendralene, as expressed by the computed adiabatic electron affinity (EA), compares to that of the reference acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) used as a p-type dopant in organic light-emitting diodes (OLEDs) and solar cells. Gas-phase density functional theory (DFT) calculations predict a stretched-out conformation as the global energy minimum for octacyano[4]dendralenes. In the solid state however, folded conformations were observed for two structures by X-ray analysis. Taking the solid state environment approximately into account calculations predict a energetical degeneracy between the stretched-out and folded conformation. Therefore conformational preference probably is a result of supramolecular dimer formation, mediated by two pairs of intermolecular, antiparallel dipolar CN⋯CN interactions.

Graphical abstract: Donor-substituted octacyano[4]dendralenes: a new class of cyano-rich non-planar organic acceptors

Supplementary files

Article information

Article type
Edge Article
Submitted
23 Jul 2010
Accepted
22 Sep 2010
First published
03 Nov 2010

Chem. Sci., 2011,2, 88-93

Donor-substituted octacyano[4]dendralenes: a new class of cyano-rich non-planar organic acceptors

B. Breiten, Y. Wu, P. D. Jarowski, J. Gisselbrecht, C. Boudon, M. Griesser, C. Onitsch, G. Gescheidt, W. B. Schweizer, N. Langer, C. Lennartz and F. Diederich, Chem. Sci., 2011, 2, 88 DOI: 10.1039/C0SC00387E

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