Synthesis and Characteristics of a Nonaggregating Tris(tetrathiafulvaleno)dodecadehydro[18]annulene

Abstract

A new tris(tetrathiafulvaleno)dodecadehydro[18]annulene with six peripheral n-hexyl substituents was prepared by oxidative Glaser-Hay cyclization of a corresponding diethynylated tetrathiafulvalene (TTF) precursor. The electronic properties of the neutral and oxidized species were studied by both UV/Vis absorption spectroscopy and electrochemistry. From these studies, it transpires that the strongly violet-colored macrocycle does not aggregate in solution to any significant degree, which was confirmed by (1)H NMR spectroscopy. This reluctance towards aggregation contrasts that observed for related TTF-annulenes containing other peripheral substitutents. Oxidation of the TTF-annulene occurs in two three-electron steps as inferred from both the peak amplitudes and the spectroelectrochemical study. We find that the tris(TTF)-fused dehydro[18]annulene is more difficult to oxidize (by +0.20 V) than the silyl-protected diethynylated mono-TTF precursor. In contrast, the first vertical ionization energy calculated at the B3 LYP/6-311+G(2d,p) level for the parent tris(TTF)-fused dehydro[18]annulene devoid of peripheral hexyl substituents is in fact lower (by 0.44 eV). Moreover, the surface morphology of 1 d drop-cast on a mica substrate was investigated by atomic force microscopy (AFM). Crystalline domains with slightly different orientations were observed. The thickness of individual layers seen in the crystalline domains and the thickness of a monolayer obtained from a very dilute solution were determined to 1.8-1.9 nm. This thickness corresponds to the diameter of the macrocycle and the layers seen in the film are apparently formed when the molecules stack in the horizontal direction relative to the substrate.

Conjugated Macrocycles: Concepts and Applications

“…[134,135] Although hexyl-substituted 184 a did not self-aggregate in solution or the solid state, [134] butylthio-substituted 184 b self- . Cross-conjugated cyclyne 176 a, its dinuclear complex 176 b, and pyrido [7 4 ]allenoacetylenic cyclophane 177.…”

All‐Carbon Scaffolds by Rational Design

“…Whereas a large variety of aryl-and heteroaryl-fused dehydro [12]and [18] annulenes have been described (see above), [39,[71][72][73][74][75] only a limited number of such chromophores, not annellated to aromatic rings, were reported in recent years. [76] Most of them were prepared as potential precursors to cyclo[n]carbons, such as cyclo-C 18 , which, however, remain elusive as bulk materials.…”

Konjugierte Makrocyclen: Konzepte und Anwendungen

“…[134,135] Wenngleich die hexylsubstituierte Verbindung 184 a weder in Lçsung noch im Festkçrper einer Selbstorganisation unterlag, [134] [136] in der nichtlinearen Optik (NLO) [137] und in organischen Feldeffekttransistoren (OFETs). [138] Darüber hinaus wurden Carbazole als elektronenschiebende chromophore Einheiten in photoinduzierten Elektronentransfersystemen eingesetzt.…”