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

摘要

A new tris(tetrathiafulva-leno)dodecadehydro[18]annulene with six peripheral n-hexyl substituents was prepared by oxidative Glaser-Hay cy-clization of a corresponding diethynyl-ated tetrathiafulvalene (TTF) precursor.The electronic properties of the neutral and oxidized species were studied by both UV/Vis absorption spec-troscopy 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 ~1H 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 dehy-dro[18]annulene is more difficult to oxidize (by+0.20 V) than the silyl-pro-tected diethynylated mono-TTF precursor.In contrast,the first vertical ionization energy calculated at the B3LYP/6-311+G(2d,p) level for the parent tris(TTF)-fused dehydro[18]an-nulene devoid of peripheral hexyl substituents is in fact lower (by 0.44 eV).Moreover,the surface morphology of 1d 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.