26
S. Droulias and L. Bougas
2.1 Introduction
Chirality, the geometric property of an object that is non-superimposable with its
mirror image, is a foundational property of life: the weak interaction between fundamental particles violates parity [1]; biomolecular structures fundamental to life,
such as amino acids, sugars, RNA and DNA, are both chiral and single-handed (i.e.
homochiral) [1]; the chemistry of life and the functionalities of its building blocks
are largely stereospecific [2]; organisms ranging from protists to plants and animals possess morphological asymmetries with respect to their left-right axis [3]. The
development of sensitive chiral sensitive techniques has, therefore, been vital for
this wide range of scientific disciplines, and has enabled the study of fundamental
symmetries of the universe [4], determination of biomolecular structures [5–7], and
even the development of safe and effective drugs [8, 9], to name few of its most
prominent applications.
1
2.1.1 Chirality and Optical Activity
Starting from the observation by Arago in 1811 of colours in the sunlight as seen
through the optic axis of a quartz crystal placed between crossed polarizers, and the
observation of optical rotation in organic liquids such as lemon oils and turpentine
by Biot in 1815, the polarimetric techniques of optical rotatory dispersion (ORD)
and circular dichroism (CD) have remained as the most widely used research tools
in science for chiral sensing [11]. By 1825, Fresnel had discovered that linearly
polarized light can be regarded as a superposition of the two possible forms of
circularly polarized light [right (RCP) and left (LCP)], which lead to his proposal
of the first phenomenological theory about optical activity, i.e. the ability of a chiral
medium to rotate linearly polarized light travelling through it. His theory correctly
attributed this effect to the propagation at different speeds in the optically active
medium of the left- and right-circularly polarized components of the incident linearly
polarized light. The expression for optical activity as proposed by Fresnel has the
general form:
ϕ =
πl
λ
(n − − n + ),
(2.1)
where n ± are the (complex) indices of refraction of a chiral medium for RCP and
LCP light, respectively, λ is the vacuum wavelength of light, and l the length of the
medium.
With the advent of electromagnetism, a description of natural optically active
materials on the macroscopic level became possible and is now contained in the
1 Portions of this chapter have been reprinted with permission from [10]. Copyright 2019 American
Chemical Society.
S. Droulias and L. Bougas
2.1 Introduction
Chirality, the geometric property of an object that is non-superimposable with its
mirror image, is a foundational property of life: the weak interaction between fundamental particles violates parity [1]; biomolecular structures fundamental to life,
such as amino acids, sugars, RNA and DNA, are both chiral and single-handed (i.e.
homochiral) [1]; the chemistry of life and the functionalities of its building blocks
are largely stereospecific [2]; organisms ranging from protists to plants and animals possess morphological asymmetries with respect to their left-right axis [3]. The
development of sensitive chiral sensitive techniques has, therefore, been vital for
this wide range of scientific disciplines, and has enabled the study of fundamental
symmetries of the universe [4], determination of biomolecular structures [5–7], and
even the development of safe and effective drugs [8, 9], to name few of its most
prominent applications.
1
2.1.1 Chirality and Optical Activity
Starting from the observation by Arago in 1811 of colours in the sunlight as seen
through the optic axis of a quartz crystal placed between crossed polarizers, and the
observation of optical rotation in organic liquids such as lemon oils and turpentine
by Biot in 1815, the polarimetric techniques of optical rotatory dispersion (ORD)
and circular dichroism (CD) have remained as the most widely used research tools
in science for chiral sensing [11]. By 1825, Fresnel had discovered that linearly
polarized light can be regarded as a superposition of the two possible forms of
circularly polarized light [right (RCP) and left (LCP)], which lead to his proposal
of the first phenomenological theory about optical activity, i.e. the ability of a chiral
medium to rotate linearly polarized light travelling through it. His theory correctly
attributed this effect to the propagation at different speeds in the optically active
medium of the left- and right-circularly polarized components of the incident linearly
polarized light. The expression for optical activity as proposed by Fresnel has the
general form:
ϕ =
πl
λ
(n − − n + ),
(2.1)
where n ± are the (complex) indices of refraction of a chiral medium for RCP and
LCP light, respectively, λ is the vacuum wavelength of light, and l the length of the
medium.
With the advent of electromagnetism, a description of natural optically active
materials on the macroscopic level became possible and is now contained in the
1 Portions of this chapter have been reprinted with permission from [10]. Copyright 2019 American
Chemical Society.