Extended hybrid tetrathiafulvalene π‐donors with oligothienylenevinylene conjugated spacer groups

Abstract

Hybrid tetrathiafulvalenes (HTTFs) where the TTF units are linked by thienylenevinylene spacers (see Figure) are reported. It is found that the π donor properties of the materials are improved over analogues with oligothiophene spacers, and that they exhibit a smaller band gap. The evolution of the properties as a function of spacer length and the materials syntheses are discussed.

Synthetic Principles for Bandgap Control in Linear π-Conjugated Systems

“…Thus, for n ) 3, a ∆E value of 2.0 eV, already smaller than the bandgap of PT, was obtained. 368 Furthermore, as shown by their CV, even for n ) 1, these compounds are directly oxidized into their dication state through a single-step two-electron process, thus confirming the weak Coulombic repulsion in these systems. 368 A further chain extension of these systems has been accomplished by grafting solubilizing alkyl chains on the thiophene rings of the oligo(thienylenevinylene) spacer (100 and 101).…”

“…368 Furthermore, as shown by their CV, even for n ) 1, these compounds are directly oxidized into their dication state through a single-step two-electron process, thus confirming the weak Coulombic repulsion in these systems. 368 A further chain extension of these systems has been accomplished by grafting solubilizing alkyl chains on the thiophene rings of the oligo(thienylenevinylene) spacer (100 and 101). 369 These compounds exhibit a further decrease in oxidation potential and the dication can be formed directly at less than 0.20 V while the tetracation is reached around 1.00 V (Figure 15).…”

Salts of extended tetrathiafulvalene analogues: relationships between molecular structure, electrochemical properties and solid state organisation

“…Combining the vinylogue and aromatic approaches Roncali et al have synthesized further large hybrid derivatives 46, 94 47, 95 48 96 and 49. 97 The insertion of ethylenic bonds between the heterocycles was expected to increase the rigidity of the molecules and to reduce the resonance energy of the spacer, thus favouring good electronic delocalisation.…”

“…Such behaviour for these hybrid systems indicates that the dithiafulvenyl groups have a major contribution to the HOMO level, which is strongly affected by the nature of the substituents R, while the LUMO level is essentially dependent upon the length of the spacer. The electrochemical reduction of compounds 46 with n 5 2 shows that all the derivatives are reduced at the same potential of 21.20 V/SCE, independent of the substituents R. 94 The extension of the spacer has also been achieved by using thienylenevinylene (TV) units substituted on the b positions of the thiophene by n-hexyl groups in order to increase the solubility of the molecules 50. 98 With this approach, the longest extended TTF analogues, with the spacer containing up to 70 sp 2 carbons (n 5 5), have been synthesized.…”

5-Formyl-2-furylboronic acid as a versatile bifunctional reagent for the synthesis of π-extended heteroarylfuran systemsElectronic supplementary information (ESI) available: synthesis and characterisation data for 3–17. See http://www.rsc.org/suppdata/ob/b3/b302767h/

“…There is a red shift in the lowest energy absorption band in dichloromethane solution in the sequence 6 (λ max 329 nm), 16 (λ max 403 nm) and 17 (λ max 430 nm) which is consistent with enhanced electron donating ability of the dimethyl-1,3-dithiole unit in 17 compared with its dimethoxycarbonyl analogue 16. 20 In summary, we have demonstrated a new route to π-extended heteroarylfuran systems by exploiting the rare combination of functional groups in compound 2. Further extension of this sequential Suzuki-Miyaura and Wittig methodology will be applicable to other 2-heteroarylfuran derivatives and derived π-extended systems of particular relevance to conjugated molecular wires of well-defined conjugation lengths.…”