Journal of the American Chemical Society, Vol.117, No.2, 806-816, 1995
Macrocyclic Pi-Conjugated Carbopolyanions and Polyradicals Based upon Calix(4)Arene and Calix(3)Arene Rings
Calix[4]arene- and calix[3]arene-based polyether precursors to polyradicals are synthesized. pi-Conjugated carbanions, such as calix[4]arene-based tetraanion and calix[3]arene-based trianion, are prepared and studied using NMR spectroscopy and voltammetry. A 4-fold-symmetric conformer for the tetraanion and two non-interconverting conformers (3-fold- and 2-fold-symmetric) for the trianion are found on the NMR time scale. Oxidation of the tetraanion gives the corresponding calix[4]arene-based S = 2 tetraradical. However, ESR spectroscopy suggests that the predominant product from oxidation of calix[3]arene-based trianion is the corresponding triradical dimer. The related calix[3]arene-based S = 1 diradical is found to be monomeric. Additional characterization of octaradical 1(8.) and pentaradical 2(5.), which were described in a preliminary communication, is presented.