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Techniques of Chiroptical Spectroscopy
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Nelu Grinberg, Harry G. Brittain, Sonia Rodriguez
Molecules for which the mirror images cannot be superimposed are denoted as being dissymmetric or chiral, and these enantiomer structures are capable of being resolved. The fundamental requirement for the existence of molecular dissymmetry is that the molecule cannot possess any improper axes of rotation, the minimal interpretation of which implies additional interaction with light whose electric vectors are circularly polarized. This property manifests itself in an apparent rotation of the plane of linearly polarized light (polarimetry) or in a preferential absorption of either left- or right-circularly polarized light (circular dichroism). Circular dichroism (CD) can be observed in either electronic or vibrational bands. The Raman scattering of a chiral compound can also reflect the optical activity of the molecule. Should the excited state of a compound be both luminescent and chiral, then the property of circularly polarized luminescence can be observed. The circular dichroism of an optically active molecule can be used in conjunction with fluorescence monitoring to provide a differential excitation spectrum (fluorescence-detected circular dichroism).
Nanoscale Spectroscopy for Defense and National Security
Published in Sarhan M. Musa, Nanoscale Spectroscopy with Applications, 2018
Aditi Deshpande, Mohit Agarwal, Suman Shrestha, George C. Giakos
When linearly polarized light is passed through a substance containing optically active asymmetrically arranged chiral molecules or nonchiral molecules, a rotation of the polarization vector occurs. This phenomenon is called optical rotation or optical activity. Glucose and most of the biological molecules such as proteins or enzymes are optically active. The level of polarization preservation and the variation of the rotation of linearly polarized light fraction with glucose concentrations and with the chiral and non chiral molecules in the turbid samples have been detailed in a number of studies. However, most of these research efforts have been concentrated toward the development of noninvasive techniques for glucose monitoring based on reflectance spectroscopy, Raman scattering, or fluorescence rather than on imaging.
Nonlinear Dynamics in Quantum Photonic Structures
Published in Joachim Piprek, Handbook of Optoelectronic Device Modeling and Simulation, 2017
Gabriela Slavcheva, Mirella Koleva
There is a fundamental relationship between chirality and optical activity. The interaction of polarized light with chiral materials gives rise to the phenomenon of optical rotation (or optical activity), whereby the polarization plane is rotated continuously during the propagation of the light through the nanotube. In the presence of an external magnetic field, magnetically induced optical activity—also known as Faraday effect—takes place. Both effects manifest themselves as a rotation of the transmitted light; however, the origin of the two effects is fundamentally different. While the natural optical activity is a result of the nonlocal optical response of a medium lacking mirror symmetry, the magnetic optical activity results from time-reversal symmetry breaking by the magnetic field. The two phenomena are linked through the magneto-chiral optical effect which takes place when both symmetries are broken simultaneously [82].
The method of fundamental solutions for scattering of electromagnetic waves by a chiral object
Published in Applicable Analysis, 2023
E. S. Athanasiadou, I. Arkoudis
The interaction of electromagnetic fields with chiral materials has been of interest since such materials can be met in various natural and artificial objects. A material is considered to be chiral if it is non-superimposable with its mirror image. The interest of chiral materials can be met in many areas of science. In physics, optical activity occurs in chiral materials and has various applications in optics [10]. In chemistry, a characteristic example of chiral structures are the enantiomers which have applications in the pharmaceutical industry [11]. In geology, chiral crystal structures (like quartz crystals) are used in industry such as GPS and cell phone equipment [12]. Another interesting example is the chiral artificial materials met in the engineering industry [13,14]. This type of material can have a lot of interesting properties like auxetic effects or twisting in response to a linear force [15,16]. Chiral media are categorized under the wider class of bianisotropic media and they are characterized by a set of constitutive relations such as the Drude–Born–Fedorov used in the present work [17]. The scattering of time-harmonic electromagnetic waves by a chiral scatterer has been studied in [18]. The well-posedness of these problems using Beltrami fields together with their associated vector potentials and the boundary integral equations has been studied in [19–21]. Recently, inverse scattering problems in chiral media using the linear sampling method, Herglotz functions and the reciprocity gap functional method have been studied in [22,23].
A structural study into halogenated derivatives of mandelic acid as building blocks of chiral coordination polymers
Published in Journal of Coordination Chemistry, 2022
Chirality is a central part of life, with many of the molecules that sustain life, including sugars and proteins, being composed of chiral building blocks [1]. The prevalence of chiral molecules within living organisms emphasizes the need to identify the handedness of molecules and quantify the proportion of each enantiomer in a mixture as different enantiomers can exhibit differing responses to other chiral species. Enantiomers of chiral drugs and food additives demonstrate vastly different efficacy towards their intended function, in which one enantiomer is the active species, while the other enantiomer may have reduced function or even deleterious effects [2]. The widespread use of chiral molecules within the agricultural, pharmaceutical and food industries accentuate the need for the development of tools that will enable the straightforward identification of enantiopurity and separation of enantiomers.
Enantioselective behavior of environmental chiral pollutants: A comprehensive review
Published in Critical Reviews in Environmental Science and Technology, 2022
Marina Arenas, Julia Martín, Juan Luis Santos, Irene Aparicio, Esteban Alonso
Chiral compounds are mirror–image molecules with at least one chiral, asymmetric or stereogenic center that is bonded to different atoms or groups. A chiral chemical consists of at least one pair of enantiomers or optical isomers that rotate the plane of polarized light in opposite directions, but showing similar physical and chemical properties. One of the ways to term enantiomers is based on the direction they rotate the plane of polarized light, being termed levorotatory (L) and dextrorotatory (D), respectively. Alternatively, a minus sign (-) can be used for counterclockwise rotating molecules and a plus sign (+) used for clockwise rotating molecules (Challener, 2001). Additionally, E1 and E2 are used when the direction of the rotation is unknown and they refer to the first and last eluted enantiomers, respectively. The Cahn, Ingold and Prelog system for naming enantiomers assigns an R (rectus) or S (sinister) descriptor to each chiral center. The atoms or groups bonded to the chiral center are ranking according to the priority of each group (Cahn et al., 1956).