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2,9‐ and 2,10‐diphenylpentacene were synthesized by direct C−H borylation of ketal‐protected pentacene, followed by halodeboronation, resolution of the dihalo isomers, Suzuki arylation, cleavage of the ketals and decarbonylation in the solid state. They were studied as main active components in organic field effect transistors (OFETs). Diphenyl substitution of pentacene affects the unit cell dimensions only slightly, preserving a face to edge molecular packing in the first layers of thin films evaporated on SiO2 substrates. Both isomers self‐assemble into nanoribbons during the thin film growth upon vapor deposition. The similarity between the surface induced phases of the 2,9‐isomer and unsubstituted pentacene leads to similar 4‐probe hole mobilities, i. e. 0.13 cm2 V−1 s−1 for the former. Whereas 2,9‐disubstitution thus does essentially preserve the thin film characteristics of unsubstituted pentacene, 2,10‐disubstitution is detrimental to the molecular ordering in the thin films and therefore to the field effect mobility which is only 0.07 cm2 V−1 s−1. The known strong enhancement of field effect mobility observed upon diphenyl substitution of anthracene can thus not be emulated analogously with pentacene. [ABSTRACT FROM AUTHOR]

A series of regioisomeric push–pull amino-nitro [6]helicenes and a related [7]helicene derivative were prepared and their racemates resolved into enantiomers. Compared to the parent helicenes, they exhibit red-shifted UV-Vis spectra, pronounced dipole moments, altered chiroptical properties such as remarkable optical rotatory power, and can form nanocrystalline Langmuir–Blodgett films. [ABSTRACT FROM AUTHOR]

Racemic and highly enantioenriched 3‐methoxycarbonyl, 3‐carboxy, and 3‐hydroxymethyl derivatives of dibenzo[6]helicene were prepared. The Langmuir layers of these helicenes were formed at the air–water interface and transferred onto solid substrates to afford Langmuir–Blodgett films, which were then studied by ambient atomic force microscopy and (chir)optical spectroscopy. Significant differences were found in the behaviour of the Langmuir layers as well as in the morphology, UV/Vis, electronic circular dichroism (ECD), and fluorescence spectra of the Langmuir–Blodgett thin films depending on the molecular chirality and nature of the polar group. The experimental results were supported by molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Both experiments and molecular dynamics simulations point to the fact that racemic assemblies are more stable than enantiopure ones. B Helicene rafts on water b : Amphiphilic derivatives of dibenzo[6]helicene form stable Langmuir layers at the air-water interface. Both experiments and molecular dynamics simulations point to the fact that racemic assemblies are more stable than enantiopure ones. [Extracted from the article]

A series of inherently chiral (di)thiahelicenes/dithiophenohelicenes containing 5, 6, 9 or 11 (hetero)cycles in their helical backbone with thiophene subunit(s) embedded in it or annulated to its periphery were uniformly synthesized by intramolecular alkyne [2+2+2] cycloisomerization. Their structural, chemical and physicochemical properties such as crystal packing, oxidation, barrier to racemization, spontaneous thin film transformation or electrochemical behavior were studied and compared with the respective properties of the parent all‐carbon helicenes and dibenzohelicenes. [ABSTRACT FROM AUTHOR]