Volker Buß

Absolute Sense of Twist of the C12–C13 Bond of the Retinal Chromophore in Rhodopsin—Semiempirical and Nonempirical Calculations of Chiroptical Data

The sign of the dihedral angle of the 12-s-trans bonds in the protonated Schiff base of 11-cis-retinal (see picture on the right) correlates with the sign of the long-wavelength absorption in the circular dichroism spectra. This is the result of the high-quality excited-state calculations on the chromophore of the visual pigment rhodopsin.

Absoluter Drehsinn der Verdrillung um die C12-C13-Bindung des Retinalchromophors von Rhodopsin – semiempirische und nichtempirische Berechnung chiroptischer Daten

Das Vorzeichen des Diederwinkels der 12-s-trans-Bindung in der protonierten Schiff-Base von 11-cis-Retinal (siehe rechts) korreliert mit dem Vorzeichen der langwelligen Absorption im Circulardichroismus-Spektrum. Dies ist das Ergebnis hochwertiger Rechnungen am angeregten Zustand des Chromophors des Sehpigments Rhodopsin.

A tolan substituted optically active spiropyran

Abstract A substituted optically active spiropyran with a tolan group in the 6′-position is described. Both the parent spiropyran and its derivative were separated by chiral HPLC and characterized by CD spectroscopy. There is a ‘diastereomeric switch’ at temperatures below −30°C , but the compound does not show liquid crystalline properties.

Strukturuntersuchungen an chiralen Schiff-Basen des 11-cis-Retinals/Structure Investigation of Chiral Schiff Bases of 11-cis-Retinal

CD and UV spectra of four chiral 11-cis-retinal Schiff bases obtained by condensing the aldehyde with asymmetric amines are used to gain structural information about the polyene conformation. The spectra are temperature-dependent indicating the same 12-s-cis/trans equilibrium as in 11-cis-retinal. In addition, CD absorptions arise at lower temperatures whose only origin is the inherent dissymmetric nature of the retinylidene Chromophore. CNDO /S-calculations performed on the basis of force-field optimized geometries give results which can partially be rationalized on the basis of experimental data. Quantitative agreement is obtained in the case of chiral hydrogen-bonded dimers.