Syntheses, Unique Strained Molecular Structures, and Unusual Transannular Electronic Interactions of a Series of Crisscross-Overlapped Tetrathiafulvalenophanes

Abstract

A series of novel tetrathiafulvalenophanes has been synthesized, in which two tetrathiafulvalenes (TTF) are linked in a crisscross-overlapped arrangement by four alkylenedithio bridges. Their molecular structures were elucidated by X-ray crystal analyses, being characterized by the bent TTF skeletons as well as the unique stacking mode. The degree of the bend largely depends on both the length and conformational rigidity of the alkylenedithio chains. The short and rigid chains induce severe bending, which brings about a hypsochromical effect in the electronic absorption spectra. On the other hand, the long and flexible chains reduce the strain and make an inside cavity large enough to include a guest molecule. In addition, the less strained compounds can effect an intramolecular transannular Coulombic interaction between their two TTF units in solution, as demonstrated by multistage redox waves in the cyclic voltammograms. All the radical cation salts formed from these tetrathiafulvalenophanes have conductivities of the same order of 10-6−10-7 S cm-1, which are apparently independent of the donor and the counterion species.

Liposomal amphotericin B versus the combination of fluconazole and itraconazole as prophylaxis for invasive fungal infections during induction

“…This behavior can be attributed to the bending of the TTF bridge and has also been observed in other bent TTF derivatives 22. 23…”

Anion Responsive TTF-Appended Calix[4]arenes. Synthesis and Study of Two Different Conformers

“…16 However, a splitting in the second redox wave is rare because adjacent TTF 2+ units, produced by a two-electron oxidation, would be subject to repulsive electrostatic interactions, reducing the chance for overlap. 17 The split signal associated with the second redox process seen in the present instance may be ascribed to the constraint enforced by the parent calix- [4]arenes. The short linker –CONH– between the calix and the TTF moieties is expected to keep the cationic forms of the latter produced via electro-oxidation locked in a rigid environment (preventing expulsion altogether and even keeping the TTF 2+ species from diffusing apart to a significant extent).…”

Multiple-Bridged Bis-Tetrathiafulvalenes: New Synthetic Protocols and Spectroelectrochemical Investigations

“…Moreover, the confinement of two TTFs in a quadruple-bridged arrangement increases the redox potentials of 10a relative to those of 4a , that is, electrostatic repulsion between the two TTF mono- or dications is not so easily opposed by conformational changes. For comparison, a strong propensity to form an intramolecular MV state was earlier observed for a criss-cross, overlapped, quadruple-bridged bis-TTF 31a. A splitting of the second redox potential for criss-crossed, overlapped bis-TTFs was shown to depend highly on the actual linker size …”