Metal-Promoted Intermolecular Electron Transfer in Tetrathiafulvalene–Thiacalix[4]arene Conjugates and Tetrachlorobenzoquinone

In this work, two series of tetrathiafulvalene (TTF) and thiacalix[4]­arene (TCA) conjugates (TTF–TCA) were designed by CuAAC click reactions. The results obtained from NMR and ¹H NMR NOE indicated that their conformations of thiacalix[4]­arene framework may prefer to 1,3-alternate. The cyclic voltammograms of four TTF–TCA compounds containing electroactive TTF units were provided. Meanwhile, their intermolecular electron-transfer (ET) behaviors with tetrachlorobenzoquinone (Q) mediated by different metal ions, Sc³⁺, Pb²⁺, Ag⁺, Cd²⁺, and Zn²⁺, in CH₃CN–CH₂Cl₂ (V/V = 1:1) solution were studied and analyzed via UV–vis spectroscopy. It was determined that intermolecular ET between each TTF–TCA and Q ensemble was not observed without introduction of the metal ions mentioned above. The added specified metal ions most likely induced the intermolecular ET between TTF–TCA and Q ensemble, and the effects of Sc³⁺ functions were the most imperative. The intermolecular ET also proved to be reliant on the structure of TTF–TCA, where TTF–TCA <b>7a</b> and <b>7b</b> were more effective than TTF–TCA <b>6a</b> and <b>6b</b>. The difference may be credited to TTF–TCA <b>7a</b> or <b>7b</b> possessing two independent TTF pendants and providing a more synergic coordination among the TTF radical cation and Q radical anion with a metal ion