Upon passing through an optically active medium, the plane of polarization of linearly polarized light becomes rotated. In liquids and gases, with randomly oriented samples, the origin of this effect is attributed to the molecular chirality (or handedness) which arises when the molecular structure is not superposable on its mirror image. The molecular structure and its mirror image are said to have opposite absolute configurations as specified by labels R (for rectus) and S (for sinister).
Chirality in self-assembled structure
Molecular Mechanics and Molecular Dynamics simulations are performed to understand how the chirality of a single molecule can be transfered at the nanoscale. On graphite surface we have showm that the number of stereogenic centers influences significantly the self-assembly and chiral structure of the aggregates of porphyrin molecules. In solution we have reported a strong majority-rules effect in the formation of chiral dynamic nanotubes from chiral bisurea monomers. Furthermore, similar helical nanotubes can be obtained from racemic monomers in a chiral solvent.
Novel Method for Calculation of Circular Dichroism
Based on the complex polarization propagator (CPP) approach in conjunction with the concept of London orbitals, gauge origin independent results for the circular dichroism of large molecular systems are obtained at the DFT level of theory. The CPP method is universal in its uniform treatment of spectroscopies in visible, ultra-violet, and X-ray regions as illustrated by the X-ray circular dichroism spectrum of the chiral fullerene C84 in the lower panel in the figure to the right. The upper panel shows the corresponding X-ray absorption spectrum.
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Last updated: 01/20/11