Electronic Interactions in a New π‐Extended Tetrathiafulvalene Dimer

Abstract

The first pi-extended tetrathiafulvalene (exTTF) dimer in which the two exTTF units are covalently connected by 1,3-dithiole rings has been obtained in a multistep synthetic procedure involving the Ullmann cross-coupling reaction by using copper(I) thiophene-2-carboxylate (CuTC). The electronic spectrum reveals a significant electronic interaction between the exTTF units. The electrochemical study carried out by cyclic voltammetry in solution and in thin-layer conditions, and the electrochemical simulation and spectroelectrochemical (SEC) measurements confirm the electronic communication and show that the oxidation of dimer 14 occurs as two consecutive 2 e(-) processes D(0)-D(0)-->D(2+)-D(0)-->D(2+)-D(2+). Theoretical calculations, performed at the B3P86/6-31G* level, confirm the experimental findings and predict that 14(2+) exists as a delocalized D(.+)-D(.+) species in the gas phase and as a localized D(2+)-D(0) species in solution (CH(3)CN or CH(2)Cl(2)). Oxidation of 14(2+) forms the tetracation 14(4+) which is constituted by two aromatic anthracene units bearing four aromatic, almost orthogonal 1,3-dithiolium cations.

A Fully Conjugated TTF–π–TCAQ System: Synthesis, Structure, and Electronic Properties

“…The dication and dianion species of 11 were computed at the B3LYP/6‐31G** level to provide a deeper understanding of the oxidation/reduction processes. As depicted in Figure 4a, the minimum‐energy structure calculated for 11 2+ corresponds to a conformation in which the TCAQ unit remains folded and the exTTF unit adopts an orthogonal conformation similar to those previously found for exTTF dications both theoretically15, 16, 22 and experimentally 18. 19 Upon oxidation, the exocyclic CC bonds that connect the dithiole rings to the anthracene unit elongate from 1.365 Å in neutral 11 to 1.482 Å in charged 11 2+ .…”

How the Anchoring Site on Two Extended Tetrathiafulvalenes Impacts the Electronic Communication through a Bis(acetylide)ruthenium Linker

“…This can be easily explained by the fact that, in TTFAQ, the HOMO is mainly located on the dithiole rings and the LUMO on the anthraquinodimethane unit. 14 In the same vein, the oxidation potential of the Ru II /Ru III couple is only anodically shifted by 190 mV in comparison with that observed for trans-[RuCl 2 (dppe) 2 ] (0.06 V) while for complex D-Ru-D 6b an anodic shift of 610 mV was observed. The generation of the TTFAQ 2+ induces the aromatization of the dithiolium rings together with that of the central anthracene, which lies in a plane perpendicular to the planes of the dithiolium rings.…”

“…On the other hand, when the TTFAQs are linked directly through the dithiole moieties (B and C Chart 1), two closely spaced redox processes are observed, indicating intramolecular electronic interactions between the donor units. 14 Recently, we reported the synthesis of TTF dimers where the two redox-active cores are connected by an organometallic linker, the trans-Ru-bis(acetylide), and we demonstrated that electronic communication occurs between the three redoxactive cores, i.e. the two TTFs and the Ru center within trans-[Ru(CCMe 3 TTF) 2 (dppe) 2 ].…”

“…This second case is rare. 13,14 On the one hand, when the two donor moieties are covalently attached by the anthracene cores with a spacer (A in Chart 1), such as an oxygen atom, 15 an ethene, 16 an alkyne, 17,18 or more recently a Pt-bis(acetylide) linker, 12 both TTFAQs are oxidized simultaneously and no electronic interplay has been evidenced. On the other hand, when the TTFAQs are linked directly through the dithiole moieties (B and C Chart 1), two closely spaced redox processes are observed, indicating intramolecular electronic interactions between the donor units.…”

Oxygen, sulfur, selenium, tellurium and polonium

“…The same group also reports the synthesis and crystal structure of a new precursor for functionalised DTDAFs. 43 Reports of extended TTFs, in which the conjugated core between the two dithiole rings has been extended, include the incorporation of extra double bond(s), 44 triple bond(s), 45 para-quinoid spacer unit(s), 46 a two-way or three-way junction separating dithiole rings using a benzene ring, 47 or combinations of the above. 48 Ouahab et al report the opening of the central CQC bond in a TTF derivative by Cu 2+ salts 49 to form a 1,4,6,9-tetrathia-10-ketospiro [4,5]decane.…”