Twisted Thienylene–Phenylene Structures: Through‐Space Orbital Coupling in Toroidal and Catenated Topologies

Abstract

Sterically crowded and twisted thienylene‐phenylenes were synthesized and characterized in comparison to corresponding polyphenylene nanostructures. Spectroscopic, diffraction, and theoretical studies gave evidence of through‐space delocalization of π‐electrons of peripheral (hetero)aromatic rings in toroidal and catenated topologies.

Pyrimidine-Substituted Hexaarylbenzenes as Versatile Building Blocks for N–Doped Organic Materials

“…As a reference for the optical properties of our less substituted HABs, the literature-known compound 6d with four tert-Bu substituents was synthesized as well using a literature-known procedure in 80% yield (81% lit.). 18 Inspired by previous works, 33 we subjected the butadiyne 4 to Diels-Alder reaction conditions as well, expecting a two-fold [4 þ 2] cycloaddition. Upon stirring the reactants in diphenyl ether at 230°C for 12 h, the product of a single cycloaddition reaction 7 was isolated in an unoptimized yield of 22%.…”

“…In the case of 7, the emission maximum was similarly bathochromically shifted by 31 nm compared to 10 to 375 nm. 33 Emission intensities were normalized with respect to the compounds' absorbances at the constant excitation wavelength, showing stronger emission for 7.…”

“…It should be noted that in a very similar system that featured only thiophene substituents on the same basic structural skeleton as 7, the alkyne-spaced thiophene ring is twisted by about 47.7°with respect to the central benzene core. 33 The above-mentioned tolane 3 with coplanar heterocycles crystallized in the monoclinic space group P2 1 /n from a concentrated chloroform solution. Up to now, crystals of 3 have only been obtained by co-crystallization with calix [4] resorcinarene 39 or 1,3-diiodotetrafluorobenzene exploiting N•••I halogen bonds for single crystal formation.…”

“…Electronic absorption and emission spectra were measured in CH2Cl2 (Figure 3), showing a rather unresolved absorption of 6a-d within the UV up to 325 nm (Figure 4), as can be observed for the all-carbon analogue 9 (Table 1). 33 Alkynefunctionalization in 7 resulted in an expanded absorption up to 350 nm due to the extended π-system and, in contrast to its allcarbon analogue 10, was accompanied by an increase in molar absorption coefficient. Upon excitation of 5•10 -6 M samples at 280 nm, fluorescence maxima were found around 365 nm for 6a-d, which is in the range of other pyrimidine-functionalized HABs, 12 while shifted to lower energy by 32 nm compared to 9.…”

“…In case of 7, the emission maximum was similarly bathochromically shifted by 31 nm compared to 10 to 375 nm. 33 Emission intensities were normalized with respect to the compounds' absorbances at the constant excitation wavelength, showing stronger emission for 7. In a cyclic voltammetry analysis of a 1 mM solution of 6d in methylene chloride, no oxidation or reduction events could be observed within the accessible potential window given by decomposition of the solvent (see Figure S25).…”