Vibrational circular dichroism applications

Exam pies of Vibrational Circular Dichroism Applications 283... 

Keiderling TA (1996) Vibrational circular dichroism - applications to conformational analysis of biomolecules. In Fasman GD (ed) Circular Dichroism and the Conformational Analysis of Biomolecules, pp 555-598. New York VCH. 

Vibrational optical activity (VOA) is a relatively new area of natural optical activity. It consists of the measurement of optical activity in the spectral regions associated with vibrational transitions in chiral molecules. There are two basic manifestations of VOA. The first is simply the extension of electronic circular dichroism (CD) into the infrared region where fundamental one-photon vibrational transitions are located. This form of VOA is referred to as vibrational circular dichroism (VCD). It was first measured as a property of individual molecules in 1974 [1], and was independently confirmed in 1975 [2]. Within the past twelve years, VCD has been reviewed on a number of occasions from a variety of perspectives [3-15], and two more reviews are currently in press [16,17], The second form of VOA has no direct analog in classical forms of optical activity. Optical activity in Raman scattering, known simply as Raman optical activity (ROA), was measured successfully for the first time in 1973 [18], and confirmed independently in 1975 [19], ROA has been described in detail and reviewed several times in the past decade from several points of view [20-24], and two additional reviews [25,26], one with a view toward biological applications [25] and the other from a theoretical perspective [26], are currently in press. In addition, two articles of a pedagogical nature are in press that have been written for a general audience, one on infrared CD [27] and the other on ROA [28],... 

Recenfly fhe ah initio calculation mefhod of vibrational circular dichroism (VCD), optical rotatory dispersion (ORD), and electronic circular dichroism (ECD) has been developed as fhe third nonempirical method [3, 4]. The method is applicable to compounds having no chromophore, and so should be widely used in future. 

In this chapter, we discuss a relatively new methodology for the structural characterization of chiral organic molecules, namely, vibrational circular dichroism (VCD) spectroscopy [1], To date, very few studies of the VCD spectra of pharmaceutical compounds have been reported. Our goal will therefore be to describe the general techniques and applications of VCD spectroscopy in order to illuminate its potential value to specific problems of pharmaceutical chemistry. 

T. A. Keiderling, in Practical Fourier Transform Spectroscopy, J. R. Ferraro and K. Krishnan, Eds., Academic Press, New York, 1989, pp. 203-284. Vibrational Circular Dichroism Comparison of Techniques and Practical Applications. 

At present, the density functional theory (DFT) prevails in calculations of the structural and spectral parameters of transition metal complexes [18]. For this reason, and thanks to our previous positive experience with simulation and interpretation of the UV-Vis, IR, electronic and vibrational circular dichroism (BCD and VCD) spectra of chiral vanadium complexes [19], we decided to use the DFT methods as the main tool in the present work as weU. We shall present the calculated molecular stractures, vibrational and electronic spectra, as well as the V chemical shifts of the chosen anions of the vanadium(V) tartrato complexes. Where applicable, results are confronted with the available experimental data, with the aim to assess the reliability of the individual methods for future calculations of a similar kind. 

In this chapter, a sensitive method for measurement by continuous-scan Fourier-transform infrared (FT-IR) spectrometry called polarization-modulation spectrometry is introduced this is a useful method for measuring, with high signal-to-noise ratio, not only the reflection-absorption spectra of thin films adsorbed onto metal substrates but also other spectra such as vibrational circular dichroism (VCD) spectra. Polarization-modulation spectrometry is a type of double-modulation FT-IR spectrometry [1], In this chapter, descriptions of double-modulation spectrometry are given first, then polarization-modulation spectrometry is discussed, and then its application to the measurement of reflection-absorption spectra of thin films on metal substrates is discussed. 

Nafie LA and Freedman TB (1998) Vibrational circular dichroism an incisive tool for stereochemical applications. Enantiomer 3 283-297. 

Keiderling TA (1994) Vibrational circular dichroism spectroscopy of peptides and proteins. In Nakanishi K, Berova N and Woody RW (eds) Circular Dichroism -Principles and Applications, pp 597-521. New York VCH. 

Keiderling TA, Kubelka J, Hilario J (2006) Vibrational circular dichroism of biopolymers. Summary of methods and applications, fir Braiman MS, Gregoriou VG (eds) Vibrational spectroscopy of biological and polymeric materials. CRC, New York... 

The group started with one professor (Patrick Bultinck) appointed in October 2001 and one Ph.D. student and started activities over a widespread range of areas including computational medicinal chemistry and chiroptical vibrational spectroscopy. At the beginning, the research was rather application directed with emphasis on conformational analysis, QSAR, and electronegativity equalization in medicinal chemistry and combined experimental/ computational studies in Vibrational Circular Dichroism (VCD). 

Vibrational circular dichroism (VCD) and Raman optical activity (ROA) are the two principal forms of vibrational optical activity (VOA). In a similar fashion to what has been discussed for other chiroptical methods, VOA is a spectroscopic measure of the differential response of a chiral molecule to left- versus right-circularly polarized radiation, however, during a vibrational transition. VCD and ROA have become powerful tools for the determination of AC of chiral molecules in the solution state after nearly 40 years of evolution, although the application of ROA still lags behind that of VCD." ... 

There have been numerous applications of continuum models to equilibria and reactions in solution surveys of these and extensive listings are provided by Cramer and Truhlar.16 Other studies have focused upon the effects of solvents upon solute molecular properties, such as electronic and vibrational spectra,16 dipole moments, nuclear quadrupole and spin-spin coupling constants and circular dichroism.12... 

The primary motivation for the development and application of vibrational optical activity lies in the enhanced stereochemical sensitivity that it provides in relation to its two parent spectroscopies, electronic optical activity and ordinary vibrational spectroscopy. Over the past 25 years, optical rotatory dispersion and more recently electronic circular dichroism have provided useful stereochemical information regarding the structure of chiral molecules and polymers in solution however, the detail provided by these spectra has been limited by the broad and diffuse nature of the spectral bands and the difficulty of accurately modeling the spectra theoretically. 

---