[a][ ‡]Dedicated to Kenkichi Sonogashira on the occasion of his 80th birthday

In the field of material science functionalization of substrate surfaces (e.g. metal, graphite) with organic molecules is of increasing interest. Desirable targets are molecules with functional groups providing for two‐dimensional assembly and three‐dimensional crystal growth. We have synthesized a series of halogen‐end‐capped oligo‐phenylene‐ethynylenes (OPEs) to study the interactions at the solid/liquid interface and in crystal structures. Organohalides can be involved in a wide variety of intermolecular interactions such as C–X···H, C–X···X–C and C–X···π‐orbitals. The range of halogen‐based interactions and the diversity of intermolecular forces along different crystal axes makes the investigation of such structures particular interesting and challenging. Here we probe the interplay of halide end‐groups and the backbone of an OPE to investigate the intermolecular interactions in both solution depositions (2D) and X‐ray crystal structures (3D). The STM images and the crystal structures of each OPE reveal striking packing similarities. For each molecule, a plane in the crystal structure with an arrangement of molecules resembling its two‐dimensional packing on a flat surface was found. These results support the hypothesis of sheet‐by‐sheet crystal growth and suggest that flat surfaces would be ideal interfaces to promote crystal growth for halide‐end‐capped OPEs.

The synthesis of macrocycles comprising a 1,1′‐bis(phenylethynyl)ferrocene subunit was developed to increase the structural control over the spatial arrangement of the two cyclopentadienyl ligands of the ferrocene junction. The target structures were obtained through a modular strategy that enables the assembly of varying ring sizes from a common precursor. In particular, macrocycles were either formed by an ether formation reaction or by ring‐closing metathesis reactions. The macrocycles were obtained in reasonable isolated yields, which allowed their thorough characterization by one‐ and two‐dimensional NMR spectroscopy experiments, and the identity of one macrocycle was corroborated by single‐crystal X‐ray diffraction.

No abstract

Review: 116 refs.