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CHEMISTRY Planar arrays of fused aromatic rings are stabilized by electron delocalization in their extended π-network, which leads to the bright colors that make these molecules such useful dyes. However, chemists interested in the competing interplay of steric and electronic factors have long tried to coax such molecules out of planarity by appending bulky substituents. Dai et al. have managed to crowd four pendant phenyls along a 10-carbon stretch of a diindenophenanthrene framework. The compound was formed in 20% yield from a precursor with four alkyne spacers, which were fused into the heptacyclic core through a series of intramolecular rearrangements. Crystallography revealed a severely twisted, nonplanar core geometry, particularly in the central phenanthrene ring. The dangling phenyl substituents are stacked parallel to one another in a partial helix, with the outer phenyls oriented 184° apart, presumably the result of both steric and π-stacking interactions. Nuclear magnetic resonance spectroscopy revealed a rotational barrier of ∼14 kcal/mol for the outer phenyls and a higher barrier for the two rings between them. — JSY Org. Lett. 10.1021/ol0481434 (2004).

CHEMISTRY To run a bimolecular reaction, a chemist typically mixes the two reagents in a flask and relies on collisions to bring them together. Sullivan et al. have taken a more forceful approach to inducing molecular encounters. They are able to create peptide (amide) linkages by first preparing a self-assembled monolayer (SAM) of thioamines on a gold surface, and then pressing down on it with a stamp that has been coated with a carboxylate ink. After the stamp is withdrawn and the surface rinsed, infrared spectroscopy and ellipsometry confirm the formation of C-N bonds. The stamp is a surface-oxidized poly(dimethylsiloxane) (PDMS) elastomer used in microcontact printing, and the ink contains any of a variety of N-protected amino acids. When reactions of this sort are run in solution, they generally require a coupling catalyst; none is used in the stamping process. Three successive stamp, rinse, and deprotection cycles produced a layer of Arg-Gly-Asp capable of binding mouse fibroblasts. — JSY Angew. Chem. Int. Ed. 43 , 2 (2004).