A series of racemic [7]helicenes have been prepared and characterized both in solution and in the solid state. Despite the helicenes having the ability to self-assemble in a variety of stereochemical and topological relationships, they formed only enantiomerically pure dimers held together by two pairs of cooperative hydrogen bonds. The self-assembly process was enantiospecific in solution and diastereoselective in the crystal.

Bis zu 98 % Diastereoselektivität wurden beim lichtinduzierten Ringschluss stereochemisch reiner Kupfer(I)‐Helicate eines chiralen oxazolinsubstituierten 1,2‐Dithienylethen‐Systems beobachtet (siehe Schema). Die Änderung der optischen Rotation bei dieser Photochromie ermöglicht das Lesen gespeicherter Information unter zerstörungsfreien Bedingungen.

The keto-enol equilibrium between 2,6-bis(2Ј-pyridyl)-4-pyridone 1b and 2,6-bis(2Ј-pyridyl)-4-hydroxypyridine 1a was evaluated using infrared spectroscopy, variable temperature 1 H and 13 C NMR spectroscopy and X-ray crystallography. These studies show that the less polar hydroxy tautomer 1a is the predominant species in the gas phase. The solution-state studies show the more polar keto form 1b to be predominant but not exclusive, and the ratio of tautomers depends on the polarity and hydrogen-bonding ability of the solvent as well as temperature. In the solid-state both species are present in a 1 : 1 ratio and form a dimeric structure held together by a strong C᎐ ᎐ O ؒ ؒ ؒ H-O hydrogen bond between the tautomers.

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Diastereoselectivities as high as 98 % were the result of the photochemical ring‐closure of stereochemically pure copper(I) helicates of a chiral oxazoline‐substituted 1,2‐dithienylethene photochrome (see scheme). The variations in optical rotation that accompany the photochromic event provide a means to read stored information in a nondestructive manner.

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Four (bipy)2RuII and (phen)2RuII moieties have been attached to the magnesium tepraazaporphyrin periphery by exploiting thioether coordination to obtain pentads 1 and 2 respectively. These molecules exhibit strong inter-chromophore electronic interaction as reflected by the changes in their spectral and oxidation potential shifts.

Bis zu 98 % Diastereoselektivität wurden beim lichtinduzierten Ringschluss stereochemisch reiner Kupfer(I)‐Helicate eines chiralen oxazolinsubstituierten 1,2‐Dithienylethen‐Systems beobachtet (siehe Schema). Die Änderung der optischen Rotation bei dieser Photochromie ermöglicht das Lesen gespeicherter Information unter zerstörungsfreien Bedingungen.