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Molecular Symmetry
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Molecular Symmetry

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Materials Science".

Deadline for manuscript submissions: closed (30 June 2012) | Viewed by 46567

Special Issue Editor

Prof. Dr. Vance Williams

E-Mail Website
Guest Editor
Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
Interests: organic synthesis; liquid crystals; conjugated polymers; gels; self-assembly; molecular recognition; electronic materials; photochromism; novel aromatic systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Ever since Dalton suggested that the 6-fold symmetry of ice crystals results from the packing of water molecules into hexagonal lattices, the concept of symmetry has been one of the central unifying themes of chemistry. Symmetry arguments, whether explicitly stated or implicitly assumed, underlie many of our most important chemical concepts and inform our understanding of the relationship between the molecular world and observable macroscopic properties. Indeed, it is impossible to engage in a meaningful discussion of many topics, such as abiogenesis, stereochemistry, color and crystallography, without reference to symmetry. Symmetry considerations underpin every step, from conception to culmination, in the process of creating new molecules. The language of synthesis is rife with symmetry-laden terms: chiral, racemic, isotactic, the Woodward-Hoffmann rules, stereoselective synthesis, enantiomer, epimerization, mirror planes and C2-axes, to name just a few examples. Characterization methods also rely heavily on understanding molecular symmetry: are protons homotopic, enantiotopic or diastereotopic? Is an optical transition allowed or forbidden? Materials properties, such as surface chemistry, ferroelectricity, birefringence and second harmonic generation, likewise depend on molecular and supramolecular symmetry. Symmetry can also manifests itself in the most unexpected places; for example, because low symmetry molecules are commonly more soluble than their higher symmetry analogues, isomers with differing symmetry often are conveniently separated by recrystallization.

Many of the examples listed above are well understood by chemists, while others are much less so. This special issue of the International Journal of Molecular Sciences is dedicated to exploring the major lacunae that remain in our understanding of molecular symmetry. Topics to be addressed may include, but are not limited to, challenges in organic synthesis, the effects of symmetry on self-assembly processes, symmetry breaking in the origins of life and the properties of bulk materials.

Vance Williams, Ph.D.
Guest Editor

Related Journal

Symmetry

Keywords

  • synthesis
  • spectroscopy
  • materials properties
  • optics
  • abiogenesis
  • stereochemistry

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Published Papers (6 papers)

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17475 KiB  
Article
Molecular Eigensolution Symmetry Analysis and Fine Structure
by William G. Harter and Justin C. Mitchell
Int. J. Mol. Sci. 2013, 14(1), 714-806; https://doi.org/10.3390/ijms14010714 - 4 Jan 2013
Cited by 5 | Viewed by 5836
Abstract
Spectra of high-symmetry molecules contain fine and superfine level cluster structure related to J-tunneling between hills and valleys on rovibronic energy surfaces (RES). Such graphic visualizations help disentangle multi-level dynamics, selection rules, and state mixing effects including widespread violation of nuclear spin [...] Read more.
Spectra of high-symmetry molecules contain fine and superfine level cluster structure related to J-tunneling between hills and valleys on rovibronic energy surfaces (RES). Such graphic visualizations help disentangle multi-level dynamics, selection rules, and state mixing effects including widespread violation of nuclear spin symmetry species. A review of RES analysis compares it to that of potential energy surfaces (PES) used in Born-Oppenheimer approximations. Both take advantage of adiabatic coupling in order to visualize Hamiltonian eigensolutions. RES of symmetric and D2 asymmetric top rank-2-tensor Hamiltonians are compared with Oh spherical top rank-4-tensor fine-structure clusters of 6-fold and 8-fold tunneling multiplets. Then extreme 12-fold and 24-fold multiplets are analyzed by RES plots of higher rank tensor Hamiltonians. Such extreme clustering is rare in fundamental bands but prevalent in hot bands, and analysis of its superfine structure requires more efficient labeling and a more powerful group theory. This is introduced using elementary examples involving two groups of order-6 (C6 and D3~C3v), then applied to families of Oh clusters in SF6 spectra and to extreme clusters. Full article
(This article belongs to the Special Issue Molecular Symmetry)
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16474 KiB  
Article
Electronic Structure and Phase Transition in Ferroelectic Sn2P2S6 Crystal
by Konstantin Glukhov, Kristina Fedyo, Juras Banys and Yulian Vysochanskii
Int. J. Mol. Sci. 2012, 13(11), 14356-14384; https://doi.org/10.3390/ijms131114356 - 6 Nov 2012
Cited by 42 | Viewed by 7845
Abstract
An analysis of the P2S6 cluster electronic structure and its comparison with the crystal valence band in the paraelectric and ferroelectric phases has been done by first-principles calculations for Sn2P2S6 ferroelectrics. The origin of ferroelectricity has been outlined. It was established that the [...] Read more.
An analysis of the P2S6 cluster electronic structure and its comparison with the crystal valence band in the paraelectric and ferroelectric phases has been done by first-principles calculations for Sn2P2S6 ferroelectrics. The origin of ferroelectricity has been outlined. It was established that the spontaneous polarization follows from the stereochemical activity of the electron lone pair of tin cations, which is determined by hybridization with P2S6 molecular orbitals. The chemical bonds covalence increase and rearrangement are related to the valence band changes at transition from the paraelectric phase to the ferroelectric phase. Full article
(This article belongs to the Special Issue Molecular Symmetry)
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223 KiB  
Article
The Structure Lacuna
by Jan C.A. Boeyens and Demetrius C. Levendis
Int. J. Mol. Sci. 2012, 13(7), 9081-9096; https://doi.org/10.3390/ijms13079081 - 20 Jul 2012
Cited by 2 | Viewed by 6974
Abstract
Molecular symmetry is intimately connected with the classical concept ofthree-dimensional molecular structure. In a non-classical theory of wave-like interactionin four-dimensional space-time, both of these concepts and traditional quantum mechanicslose their operational meaning, unless suitably modified. A required reformulation shouldemphasize the importance of four-dimensional [...] Read more.
Molecular symmetry is intimately connected with the classical concept ofthree-dimensional molecular structure. In a non-classical theory of wave-like interactionin four-dimensional space-time, both of these concepts and traditional quantum mechanicslose their operational meaning, unless suitably modified. A required reformulation shouldemphasize the importance of four-dimensional effects like spin and the symmetry effects ofspace-time curvature that could lead to a fundamentally different understanding of molecularsymmetry and structure in terms of elementary number theory. Isolated single moleculeshave no characteristic shape and macro-biomolecules only develop robust three-dimensionalstructure in hydrophobic response to aqueous cellular media. Full article
(This article belongs to the Special Issue Molecular Symmetry)
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341 KiB  
Article
Molecular Arrangement in Self-Assembled Azobenzene-Containing Thiol Monolayers at the Individual Domain Level Studied through Polarized Near-Field Raman Spectroscopy
by Marc Chaigneau, Gennaro Picardi and Razvigor Ossikovski
Int. J. Mol. Sci. 2011, 12(2), 1245-1258; https://doi.org/10.3390/ijms12021245 - 21 Feb 2011
Cited by 17 | Viewed by 9127
Abstract
6-[4-(phenylazo)phenoxy]hexane-1-thiol self-assembled monolayers deposited on a gold surface form domain-like structures possessing a high degree of order with virtually all the molecules being identically oriented with respect to the surface plane. We show that, by using polarized near-field Raman spectroscopy, it is possible [...] Read more.
6-[4-(phenylazo)phenoxy]hexane-1-thiol self-assembled monolayers deposited on a gold surface form domain-like structures possessing a high degree of order with virtually all the molecules being identically oriented with respect to the surface plane. We show that, by using polarized near-field Raman spectroscopy, it is possible to derive the Raman scattering tensor of the ordered layer and consequently, the in-plane molecular orientation at the individual domain level. More generally, this study extends the application domain of the near-field Raman scattering selection rules from crystals to ordered organic structures. Full article
(This article belongs to the Special Issue Molecular Symmetry)
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528 KiB  
Article
Symmetry-Adapted Rotator Functions for Molecules in Cylindrical Confinement
by Bart Verberck
Int. J. Mol. Sci. 2011, 12(1), 317-333; https://doi.org/10.3390/ijms12010317 - 13 Jan 2011
Cited by 1 | Viewed by 7953
Abstract
We present a general description of the formalism of symmetry-adapted rotator functions (SARFs) for molecules in cylindrical confinement. Molecules are considered as clusters of interaction centers (ICs), can have any symmetry, and can display different types of ICs. Cylindrical confinement can be realized [...] Read more.
We present a general description of the formalism of symmetry-adapted rotator functions (SARFs) for molecules in cylindrical confinement. Molecules are considered as clusters of interaction centers (ICs), can have any symmetry, and can display different types of ICs. Cylindrical confinement can be realized by encapsulation in a carbon nanotube (CNT). The potential energy of a molecule surrounded by a CNT can be calculated by evaluating a limited number of terms of an expansion into SARFs, which offers a significant reduction of the computation time. Optimal molecular orientations can be deduced from the resulting potential energy landscape. Examples, including the case of a molecule with cubic symmetry inside a CNT, are discussed. Full article
(This article belongs to the Special Issue Molecular Symmetry)
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259 KiB  
Article
A Molecular–Structure Hypothesis
by Jan C. A. Boeyens
Int. J. Mol. Sci. 2010, 11(11), 4267-4284; https://doi.org/10.3390/ijms11114267 - 1 Nov 2010
Cited by 11 | Viewed by 8303
Abstract
The self-similar symmetry that occurs between atomic nuclei, biological growth structures, the solar system, globular clusters and spiral galaxies suggests that a similar pattern should characterize atomic and molecular structures. This possibility is explored in terms of the current molecular structure-hypothesis and its [...] Read more.
The self-similar symmetry that occurs between atomic nuclei, biological growth structures, the solar system, globular clusters and spiral galaxies suggests that a similar pattern should characterize atomic and molecular structures. This possibility is explored in terms of the current molecular structure-hypothesis and its extension into four-dimensional space-time. It is concluded that a quantum molecule only has structure in four dimensions and that classical (Newtonian) structure, which occurs in three dimensions, cannot be simulated by quantum-chemical computation. Full article
(This article belongs to the Special Issue Molecular Symmetry)
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