Nina P. M. Huck

Dynamic Control and Amplification of Molecular Chirality by Circular Polarized Light

The enantiomers of a racemic photoresponsive material represent two distinct states that can be modulated with irradiation at a single wavelength by changing the handedness ofthe light. Dynamic control over molecular chirality was obtained by the interconversion of enantiomers of helically shaped molecules with either left or right circular polarized light (CPL). Photoresolution of the bistable compound as a dopant in a nematic liquid crystalline phase by CPL irradiation led to a chiral mesoscopic phase. The chiral information inherent to CPL is therefore transmitted to the bistable molecule, followed by amplification and macroscopic expression of the chirality.

Chiroptical Molecular Switches

The control of chirality by optical molecular switches offers intriguing prospects in the design of new materials. For example, photochemically induced stilbene-type cis-trans isomerization of 1 (see Figure) results simultaneously in reversal of the helicity. The molecular design of switching units, the possibility of highly stereoselective optical molecular switching, and an approach to a gated response are described.

Synthesis, crystal and molecular structure and dynamic behaviour of new dimethyldioxanedione based inherently dissymmetric overcrowded alkenes.

Abstract Two representatives of new chiral sterically overcrowded ethylenes, 2-methyl(9- thioxanthylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione ( 3 ) and 12H-benzo[a]thioxanthylidene-2,2-dimethyl-1,3-dioxane-4,6-dione ( 5 ), have been prepared and dynamic 1 H NMR studies revealed racemization barriers of 10.3 kcal mol −1 ( 3 ) and 23.2 kcal mol −1 ( 5 ).