New Crown Annelated Tetrathiafulvalenes:  Synthesis, Electrochemistry, Self-Assembly of Thiol Derivatives, and Metal Cation Recognition

Abstract

The synthesis of new S(2)O(4)-crown annelated tetrathiafulvalene (TTF) derivatives substituted with one terminal thiol group is described. Self-assembled monolayers (SAMs) of these compounds have been assembled on gold and platinum surfaces, the latter substrate giving improved quality films. SAMs of TTF derivative 16b are the most stable of those we have studied. Electrochemical data for SAMs of 5a, 5b, 8, 16a, and 16b in acetonitrile reveal two reversible one-electron waves, typical of the TTF system; the current increased linearly with scan rate, indicating a surface wave response. SAMs of 8, 16a, and 16b exhibited an electrochemical response in aqueous electrolytes, which was observed between 50 and 100 cycles. Moreover, if the potential scanned was limited to the first TTF oxidation, the cyclic voltammetry response was observed for at least 1000 cycles. Metal complexation by the crown ionophore of the SAMs in acetonitrile has been monitored by a positive shift in the first oxidation potential of the TTF unit (maximum DeltaE(1)(1/2) = 80 mV for Ag(+)). We also report the X-ray crystal structure of TTF-crown derivative 21 bearing two hydroxymethyl substituents, synthesized during the course of this work. The structure is characterized by infinite chains of molecules linked by strong intrachain hydrogen bonds between the terminal hydroxy groups.

Electrochemistry and time dependent DFT study of a (vinylenedithio)-TTF derivative in different oxidation states

“…This limited stability has also been observed by Bryce and co-workers for similar compounds [14,16]. The importance of traces of moisture for the stability of the second redox process has been outlined by Khodorkovsky and co-workers [85].…”

“…The non-aromatic 14 -electron system undergoes aromatisation when going from the neutral species to the dithiolium form in the singly and doubly oxidised states. TTF and its derivatives have featured in a wide variety of applications from crown-ether annelated electrochemical sensors [13][14][15][16], to molecular electronics [17][18][19][20][21] including organic field-effect transistors [22] and other advanced molecular assemblies [23][24][25].…”

Metal ion recognition and molecular templating in self-assembled monolayers of cyclic and acyclic polyethers

“…Relatively recently, Reinhoudt et al (19)(20)(21)(22) and Bryce et al (23,24) reported, almost simultaneously, the incorporation of crownether groups into SAMs and their use as potential metal ion sensors. The Reinhoudt group used electrochemical impedance spectroscopy (EIS) for SAM characterization and to study the ion recognition processes (19)(20)(21)(22).…”

“…25 and 26). The report by Bryce et al (23,24) described SAMs of crown-annelated tetrathiafulvalene (TTF) derivatives, which showed, by cyclic voltammetry (CV), a redox potential shift of the electroactive, surface-confined, crown-TTF group on ion complexation (23,24). The first TTF-crown SAMs reported by this group were apparently unstable after several electrochemical scans (23).…”

“…The first TTF-crown SAMs reported by this group were apparently unstable after several electrochemical scans (23). However, in a subsequent report they demonstrated that the stability and electrochemical behavior of the SAMs can be improved by the presence of an additional spacefilling alkyl chain (24). Thus, direct detection of ion binding may be achieved by monitoring the redox potential shift of a surfaceconfined electroactive group such as TTF, which is in close proximity to the ion host.…”