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A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Chemistry: Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (28 February 2021) | Viewed by 13006

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Special Issue Editors

Prof. Dr. Pier Remigio Salvi

E-Mail Website
Guest Editor

Department of Chemistry, University of Florence, Florence, Italy
Interests: vibrational spectroscopy of molecular solids; nonlinear laser spectroscopy of aromatic molecules; ultrafast relaxation dynamics in porphyrins; photoacoustic spectroscopy of polymers and nanomaterials

Dr. Cristina Gellini

E-Mail Website
Co-Guest Editor

Department of Chemistry, University of Florence, Florence, Italy
Interests: fluorescence properties of molecular probes; photoacoustic spectroscopy of polymers and nanomaterials; ultrafast relaxation dynamics of complex molecular systems; metallic nanostructured surfaces for SERS spectroscopy

Special Issue Information

Dear Colleagues,

This Special Issue on Symmetry and Molecular Absorption is aimed at highlighting the role of symmetry in structural and reactivity studies performed with spectroscopic methods. Historically, the symmetry classification of molecular states has been of great value in the analysis of absorption spectra and in making predictions on molecular geometries. It was well known that significant structural aspects of molecules, either in the ground or in the excited states, could be investigated making recourse to their symmetry properties. Successively, symmetry arguments were advanced in order to establish a theoretical framework in studies of molecular reactivity and reaction mechanisms. In this respect, the Woodward–Hoffman rules should be at least recalled as an extraordinarily solid attempt to rationalize the photochemical pathways of concerted reactions.

In past years, experimental results relying on new spectroscopic techniques related to laser capabilities and highly refined sample preparations (supersonically expanded molecular beams, molecules embedded in superfluid helium droplets or under a high-pressure environment, molecular nanostructures) have enlarged the importance of symmetry concepts. Thus, we invite active research scholars and long-time researchers in the fields schematically described in the keyword summary shown below to widely diffuse their experience and results, contributing to this Special Issue with original papers as well as review articles.

Prof. Dr. Pier Remigio Salvi
Dr. Cristina Gellini
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Symmetry in photochemistry
Breaking symmetry
Symmetry and plasmon resonance
Symmetry in multiphoton absorption
Cluster absorption
Environmental and astronomical application
Excited-state structures
High-pressure environment
Spectroscopy in superfluid helium

Published Papers (6 papers)

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Editorial

Jump to: Research

2 pages, 176 KiB

Open AccessEditorial

Symmetry and Molecular Spectroscopy

by Pier Remigio Salvi and Cristina Gellini

Symmetry 2022, 14(10), 2012; https://doi.org/10.3390/sym14102012 - 25 Sep 2022

Viewed by 1045

Abstract

Symmetry plays a fundamental role in molecular spectroscopy [...] Full article

(This article belongs to the Special Issue Symmetry and Molecular Spectroscopy)

Research

Jump to: Editorial

16 pages, 367 KiB

Open AccessArticle

Artificial Symmetries for Calculating Vibrational Energies of Linear Molecules

by Thomas M. Mellor, Sergei N. Yurchenko and Per Jensen

Symmetry 2021, 13(4), 548; https://doi.org/10.3390/sym13040548 - 26 Mar 2021

Cited by 5 | Viewed by 1362

Abstract

Linear molecules usually represent a special case in rotational-vibrational calculations due to a singularity of the kinetic energy operator that arises from the rotation about the a (the principal axis of least moment of inertia, becoming the molecular axis at the linear equilibrium [...] Read more.

3 N - 6

approach, of the form

∣ ν_{1}, ν_{2}, ν_{3}^{ℓ_{3}}; J, k, m ⟩

, tackling the unique difficulties of linear molecules involves constraining the vibrational and rotational functions with

k = ℓ_{3}

, which are the projections, in units of ℏ, of the corresponding angular momenta onto the molecular axis. These basis functions are assigned to irreducible representations (irreps) of the C

_{2 v}

(M) molecular symmetry group. This, in turn, necessitates purpose-built codes that specifically deal with linear molecules. In the present work, we describe an alternative scheme and introduce an (artificial) group that ensures that the condition

ℓ_{3} = k

is automatically applied solely through symmetry group algebra. The advantage of such an approach is that the application of symmetry group algebra in ro-vibrational calculations is ubiquitous, and so this method can be used to enable ro-vibrational calculations of linear molecules in polyatomic codes with fairly minimal modifications. To this end, we construct a—formally infinite—artificial molecular symmetry group D

_{\infty h}

(AEM), which consists of one-dimensional (non-degenerate) irreducible representations and use it to classify vibrational and rotational basis functions according to ℓ and k. This extension to non-rigorous, artificial symmetry groups is based on cyclic groups of prime-order. Opposite to the usual scenario, where the form of symmetry adapted basis sets is dictated by the symmetry group the molecule belongs to, here the symmetry group D

_{\infty h}

(AEM) is built to satisfy properties for the convenience of the basis set construction and matrix elements calculations. We believe that the idea of purpose-built artificial symmetry groups can be useful in other applications. Full article

(This article belongs to the Special Issue Symmetry and Molecular Spectroscopy)

21 pages, 1483 KiB

Open AccessArticle

The Resonant and Normal Auger Spectra of Ozone

by Simone Taioli and Stefano Simonucci

Symmetry 2021, 13(3), 516; https://doi.org/10.3390/sym13030516 - 22 Mar 2021

Cited by 4 | Viewed by 2187

Abstract

In this work, we outline a general method for calculating Auger spectra in molecules, which accounts for the underlying symmetry of the system. This theory starts from Fano’s formulation of the interaction between discrete and continuum states, and it generalizes this formalism to deal with the simultaneous presence of several intermediate quasi-bound states and several non-interacting decay channels. Our theoretical description is specifically tailored to resonant autoionization and Auger processes, and it explicitly includes the incoming wave boundary conditions for the continuum states and an accurate treatment of the Coulomb repulsion. This approach is implemented and applied to the calculation of the

K - L L

Auger and autoionization spectra of ozone, which is a

C_{2 v}

symmetric molecule, whose importance in our atmosphere to filter out radiation has been widely confirmed. We also show the effect that the molecular point group and, in particular, the localization of the core-hole in the oxygen atoms related by symmetry operations, has on the electronic structure of the Auger states and on the spectral lineshape by comparing our results with the experimental data. Full article

(This article belongs to the Special Issue Symmetry and Molecular Spectroscopy)

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12 pages, 639 KiB

Open AccessArticle

Linear and Non-Linear Middle Infrared Spectra of Penicillin G in the CO Stretching Mode Region

by Elena Ragnoni, Sara Catalini, Maurizio Becucci, Andrea Lapini and Paolo Foggi

Symmetry 2021, 13(1), 106; https://doi.org/10.3390/sym13010106 - 8 Jan 2021

Cited by 3 | Viewed by 2502

Abstract

In this work we report the linear and non-linear IR spectral response characterization of the CO bonds of

P e n i c i l l i n

G sodium salt in

D_{2} O

and in [...] Read more.

In this work we report the linear and non-linear IR spectral response characterization of the CO bonds of

P e n i c i l l i n

G sodium salt in

D_{2} O

and in

D M S O - d 6

solutions. In order to better characterize the spectral IR features in the CO stretching region, broadband middle infrared pump-probe spectra are recorded. The role of hydrogen bonds in determining the inhomogeneous broadening and in tuning anharmonicity of the different types of oscillators is exploited. Narrow band pump experiments, at the three central frequencies of

β - l a c t a m

, amide and carboxylate CO stretching modes, identify the couplings between the different types of CO oscillators opening the possibility to gather structural dynamic information. Our results show that the strongest coupling is between the

β - l a c t a m

and the carboxylate CO vibrational modes. Full article

(This article belongs to the Special Issue Symmetry and Molecular Spectroscopy)

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Figure 1

13 pages, 10434 KiB

Open AccessArticle

X-ray Crystal Structure and Hirshfeld Analysis of Gem-Aminals-Based Morpholine, Pyrrolidine, and Piperidine Moieties

by Abdullah Mohammed Al-Majid, Matti Haukka, Saied M. Soliman, Abdullah Saleh Alamary, Saeed Alshahrani, M. Ali, Mohammad Shahidul Islam and Assem Barakat

Symmetry 2021, 13(1), 20; https://doi.org/10.3390/sym13010020 - 24 Dec 2020

Cited by 3 | Viewed by 2677

Abstract

The gem-aminals of 1,2-dimorpholinoethane (1) and 1-morpholino-3-morpholinium bromide propane (2) were synthesized by reaction of two molar ratio of morpholine with the halogenating agents in the presence of basic condition (K₂CO₃) in acetone at room temperature (RT) overnight. The structures of the centro-symmetric compound 1 and the morpholinium salt derivative 2 were assigned unambiguous by single crystal X-ray diffraction analysis and compared with the 1,2-di(pyrrolidin-1-yl)ethane 3 and 1,2-di(piperidin-1-yl)ethane 4. The 1,2-dimorpholinoethane molecule has a center of symmetry at the midpoint of the C-C bond of the ethyl moiety leading to two equivalent halves. It crystallized in monoclinic crystal system and P2₁/n space group, while the unit cell parameters are determined to be a = 6.0430(3), b = 8.0805(3), c = 11.1700(4) Å, and β = 97.475(2)° with unit cell volume of 540.80(4) Å³ and Z = 2 at 170(2) K. The less symmetric analogue 2 crystallized in the lower space group P2₁ with unit cell parameters of a = 6.37450(10), b = 11.1378(2), c = 9.6549(2) Å, and β = 93.358(2)°, while the unit cell volume is 684.30(2)Å³ at 120(2) K. Using Hirshfeld analysis, the molecules of 1 are mainly packed by weak N…H (4.2%), O…H (16.8%), and H…H (79.0%) interactions. In contrast, the molecules of 2 are packed by significantly short O…H (14.4%) and Br…H (11.6%) interactions in addition to the relatively long H…H (73.3%) interactions. DFT calculations predicted the molecular geometry of the studied compounds showing a good agreement with the experimental X-ray structures. Due to symmetry considerations, compounds 1, 3, and 4 are nonpolar with zero dipole moment, while the less symmetric molecule 2 has a dipole moment of 6.914 Debye. Their electronic aspects, such as natural population charges, HOMO, and LUMO energies as well as the corresponding reactivity descriptors, were also calculated and discussed. Full article

(This article belongs to the Special Issue Symmetry and Molecular Spectroscopy)

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14 pages, 18277 KiB

Open AccessArticle

Equilibrium Geometries, Adiabatic Excitation Energies and Intrinsic C=C/C–H Bond Strengths of Ethylene in Lowest Singlet Excited States Described by TDDFT

by Yunwen Tao, Linyao Zhang, Wenli Zou and Elfi Kraka

Symmetry 2020, 12(9), 1545; https://doi.org/10.3390/sym12091545 - 18 Sep 2020

Cited by 6 | Viewed by 2464

Abstract

Seventeen singlet excited states of ethylene have been calculated via time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional and the geometries of 11 excited states were optimized successfully. The local vibrational mode theory was employed to examine the intrinsic C=C/C–H bond strengths and their change upon excitation. The natural transition orbital (NTO) analysis was used to further analyze the C=C/C–H bond strength change in excited states versus the ground state. For the first time, three excited states including

π_{y}^{'}

→ 3s,

π_{y}^{'}

→ 3p

_{y}

and

π_{y}^{'}

→ 3p

_{z}

were identified with stronger C=C ethylene double bonds than in the ground state. Full article

(This article belongs to the Special Issue Symmetry and Molecular Spectroscopy)

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