Chirality and circular dichroism of oriented molecules and anisotropic phases

Abstract

The results of the “Chirality measurement” circular dichroism along different viewing directions within molecules and phases—the anisotropy of circular dichroism can give suitable information in order to check helicity rules or to analyze the suprastructural chirality of films of organic materials, respectively. These results of the ACD spectroscopy (the CD of anisotropic phases and oriented molecules) show that in an oriented state different information about “chirality” will be gained from different viewing directions. ACD measurements of α,β‐unsaturated ketosteroids, TADDOLes and binaphthol derivatives were analyzed. The chiral induction of cholesteric phases, the helical twisting power, is introduced as another chirality measurement which may possibly be a new relative method for the determination of the absolute configuration. Chirality 12:278–286, 2000. © 2000 Wiley‐Liss, Inc.

Helical ribbons tuned by alkoxy chains in achiral twin-tapered dihydrazide derivatives

“…The chirality of a system involves intrinsically chiral molecules and chiral assemblies. 1 A chiral molecule has an asymmetric carbon atom or conformational asymmetry. Chiral assemblies are often achieved by non-covalent interactions between chiral molecules or between chiral building blocks.…”

Circular Polarization of Luminescence as a Tool To Study Molecular Dynamical Processes

“…The degree of circular polarization is actually a tensorial quantity that can vary strongly depending on the direction of propagation of the photon. [190][191][192][193] Hence degrees of circular polarization from immobile molecules differ considerably from the results in solution. [194] In fact it has been realized early on that anisotropy can play a role in CPL measurements especially under where photoselection in excitation occurs and where tumbling is slow.…”

Twists in mesomorphic columnar supramolecular assemblies

“…However, due to the anisotropy of this special type of sample, some caution must be taken to prevent the rise of orientation artefacts, such as linear dichroism or linear birefringence, and false circular dichroism. 10,11 Finally, molecular chirality may also endow ferroelectric properties to the Col r mesophase. 12 The particular electrooptical switching of the Col r mesophase of some phenanthrene 13 and pyrene derivatives 14 was proposed to respond to the existence of a helical organization at zero electric field.…”