Three compounds with phenyl and pentafluorophenyl rings bridged by (CH ) and (CH ) SiMe units were synthesized by hydrosilylation and C-C coupling reactions. Their solid-state structures are dominated by intermolecular π stacking interactions, primarily leading to dimeric or chain-type aggregates. Analysis of free molecules in the gas phase by electron diffraction revealed the most abundant conformer to be significantly stabilized by intramolecular π-π interactions. For the silicon compounds, structures characterized by σ-π interactions between methyl and pentafluorophenyl groups are second lowest in energy and cannot be excluded completely by the gas electron diffraction experiments. C H (CH ) C F , in contrast, is present as a single conformer. The gas-phase structures served as a reference for the evaluation of a series of (dispersion-corrected) quantum-chemical calculations.

Three 1,2‐diaryltetramethyldisilanes X5C6‐(SiMe2)2‐C6X5 with two C6H5, C6F5, or C6Cl5 groups were studied concerning the importance of London dispersion driven interactions between their aryl groups. They were prepared from 1,2‐dichlorotetramethyldisilane by salt elimination. Their structures were determined in the solid state by X‐ray diffraction and for free molecules by gas electron‐diffraction. The solid‐state structures of the fluorinated and chlorinated derivatives are dominated by aryl–aryl interactions. Unexpectedly, Cl5C6‐(SiMe2)2‐C6Cl5 exists exclusively as an eclipsed syn‐conformer in the gas phase with strongly distorted Si‐C6Cl5 units due to strong intramolecular interactions. In contrast, F5C6‐(SiMe2)2‐C6F5 reveals weaker interactions. The contributions to the total interaction energy were analyzed by SAPT calculations.

1,2-Diaryltetramethyldisilanes X5C6–(SiMe2)2–C6Y5 (X ≠ Y; X, Y = H, F, Cl) adopt counterintuitive dispersion-driven syn-conformations in the crystal and the gas phase, determined by X-ray and electron diffraction.

Starting from 10-bromo-1,8-dichloroanthracene, a series of 1,8-dichlorinated anthracene derivatives, flexibly bridged in position 10 by –Me2Si– and –Me2Si–(CH2) n –SiMe2– linker units, were synthesised. The linked anthracenes were generated by converting (1,8-dichloroanthracen-10-yl)lithium with chlorosilanes in salt-elimination reactions. The bichromophors were tested in UV light induced photo reactions. None of the new compounds yielded any intra- or intermolecular photoproduct. All α,ω-(dimethylsilyl)alkane-linked bisanthracenes decomposed to give 1,8-dichloro-9-hydroxyanthracen-10(9H)-one in the presence of oxygen. A completely different behaviour was shown by the bisanthracenyldimethylsilane, undergoing a 9,10:3′,4′-photocyclomerisation reaction. The new compounds were characterised by NMR spectroscopy, mass spectrometry and in most cases by X-ray diffraction studies.