Saddle-Shaped Cyclic Indole Tetramers: 3D Electroactive Molecules.
We present a joint theoretical and experimental study of a series of cyclic indole tetramers aimed at understanding the fundamental electronic properties of this 3D platform and evaluating its potential in the construction of new semiconductors. To this end, we combined absorption and Raman spectroscopy, cyclic voltammetry, and spectroelectrochemistry with DFT calculations. Our results suggest that this platform can be easily and reversibly oxidized. Additionally, it has a HOMO that matches very well with the workfunction of gold, therefore charge injection from a gold electrode is expected to occur without significant barriers. Interestingly, the cyclic tetraindoles allow for good electron delocalization in spite of their saddle-shaped structures. The steric constraints introduced by N-substitution significantly inhibits ring inversion of the central cyclooctatetraene unit, whereas it only barely affects the optical and electrochemical properties (a slightly higher oxidation potential and a blueshifted absorption upon alkylation are observed).
Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049, Madrid, Spain.
Constanza
C
Ruiz
Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049, Madrid, Spain.
Ángeles
Á
Monge
Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049, Madrid, Spain.
Enrique
E
Gutiérrez-Puebla
Instituto de Química Médica, CSIC, Juan de la Cierva 3, 28006, Madrid, Spain.
Ibon
I
Alkorta
Instituto de Química Médica, CSIC, Juan de la Cierva 3, 28006, Madrid, Spain.
José
J
Elguero
Department of Physical Chemistry, University of Málaga, 29071, Málaga, Spain.
Juan T López
JT
Navarrete
Department of Physical Chemistry, University of Málaga, 29071, Málaga, Spain.
M Carmen
MC
Ruiz Delgado
Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049, Madrid, Spain. bgl@icmm.csic.es.
Berta
B
Gómez-Lor
cyclooctatetraene; hyperconjugation; organic semiconductors; spectroelectrochemistry; tetraindoles