Special Issue "Applications of Circular Dichroism"
A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Physical Chemistry, Theoretical and Computational Chemistry".
Deadline for manuscript submissions: closed (31 January 2012)
Prof. Dr. David Kliger
Department of Chemistry and Biochemistry; University of California, Santa Cruz, Santa Cruz, CA 95064, USA
Chiroptical phenomena have been known for two centuries. However, new developments over the past 20 – 30 years have greatly expanded the capability and versatility of chiroptical spectroscopy, as evidenced by the articles in this special issue.
Biot first observed optical rotation, and he and Fresnel studied the phenomenon in the early 1800’s. In the mid 1800’s Pasteur related the phenomenon to molecular asymmetry. Since that time optical rotation (OR), and the related phenomenon of circular dichroism (CD), have been used in innumerable studies of molecular structures.
Early studies of chiroptical phenomena, of course, did not have the use of electronic devices that we now take for granted, so they involved measurements of optical rotation using null techniques detected visually. This situation changed as photoelectric light detectors were developed along with electronic devices to record light intensities in the twentieth century. With the advent of fast modulators of light polarization and phase sensitive measurement techniques, it became possible to measure differences in the absorption of left and right circularly polarized light with high sensitivity. CD spectroscopy then became a more common tool for molecular structure determinations since CD spectra can more easily be correlated with molecular structure than OR spectra and because instruments capable of producing sensitive measurements of visible and ultraviolet CD spectra, became commercially available.
The more recent developments of the past several decades have again expanded the capabilities of chiroptical spectroscopy by opening up access to spectral regions and higher order optical effects sensitive to additional features of molecular structure, by extending time resolution to the very fast time scales of fundamental molecular processes, and by advancing the theoretical understanding needed to interpret the structural implications of chiroptical spectra. Circularly polarized luminescence spectroscopy has increased the sensitivity of CD measurements of emitting chiral molecules. Structural determinations have been improved by making CD measurements farther into the UV region and even extending CD measurements into the X-ray and IR regions. IR measurements of CD monitor anisotropies of vibrational transitions and are thus particularly sensitive to local structural features. Similar capabilities have also been introduced with the development of Raman optical activity measurements. Highly sensitive measurements of local structural features around aromatic moieties have also been made possible with the development of magnetic circular dichroism. Techniques have also been developed to measure CD spectra with nanosecond or even picosecond or femtoseconds time resolution. These new developments, and improved theoretical analyses of CD spectra, have brought new capabilities to this old technique, thus made it useful for new applications. This issue explores a variety of such new applications of CD spectroscopy.
Prof. Dr. David Kliger
- chiroptical phenomena
- circular dichroism
- magnetic circular dichroism
- optical activity
- Raman optical activity
- vibrational circular dichroism
- structure determination
- time-resolved circular dichroism