Journal Description

Chemistry

Chemistry is a peer-reviewed, open access journal of chemistry, published quarterly online by MDPI.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within ESCI (Web of Science), CAPlus / SciFinder, and many other databases.
Reliable service: rigorous peer review and professional production.
Rapid Publication: manuscripts are peer-reviewed and a first decision provided to authors approximately 15.5 days after submission; acceptance to publication is undertaken in 4.9 days (median values for papers published in this journal in the first half of 2021).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Extra benefits: no space constraints, no color charges.

Imprint Information Journal Flyer Open Access ISSN: 2624-8549

Latest Articles

Open AccessArticle

A Practical Laboratory-Scale Synthesis of All Eight Stereoisomeric Forms of Terpene Linalool Oxide

Stefano Serra

Davide De Simeis

and

Sara Papili

Chemistry 2021, 3(4), 1247-1257; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040090 (registering DOI) - 16 Oct 2021

Abstract

In this work, we describe a user-friendly procedure for the preparation of all the isomeric forms of the terpene linalool oxide. The presented method is based on the transformation of the linalool enantiomers into the corresponding diastereoisomeric mixtures of the two furanoid oxides and two pyranoid oxides. Taking advantage of the different steric hindrance of the hydroxyl functional groups, the pyranoid forms were separated as a diastereoisomeric mixtures of their benzoate esters. Conversely, the cis- and trans-furanoid isomers were transformed in the corresponding acetates, which were directly separated by chromatography. The hydrolysis of the latter esters afforded cis- and trans-furanoid linalool oxides whereas the same reaction performed on the benzoates mixture afforded a separable mixture of cis- and trans-pyranoid linalool oxide. Overall, the method features, as a unique mandatory requirement, the availability of both linalool enantiomers, and can be conveniently performed from a milligram to a multigram scale. Full article

(This article belongs to the Special Issue Flavors and Fragrances: Biology, Chemistry and Biotechnology)

► Show Figures

Graphical abstract

Open AccessReview

A Comprehensive Review of Graphene-Based Anode Materials for Lithium-ion Capacitors

and

Chemistry 2021, 3(4), 1215-1246; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040089 (registering DOI) - 14 Oct 2021

Abstract

Lithium-ion capacitors (LICs) are considered to be one of the most promising energy storage devices which have the potential of integrating high energy of lithium-ion batteries and high power and long cycling life of supercapacitors into one system. However, the current LICs could only provide high power density at the cost of low energy density due to the sluggish Li⁺ diffusion and/or low electrical conductivity of the anode materials. Moreover, the serious capacity and kinetics imbalances between anode and cathode result in not only inferior rate performance but also unsatisfactory cycling stability. Therefore, designing high-power and structure stable anode materials is of great significance for practical LICs. Under this circumstance, graphene-based materials have been intensively explored as anodes in LICs due to their unique structure and outstanding electrochemical properties and attractive achievements have been made. In this review, the recent progresses of graphene-based anode materials for LICs are systematically summarized. Their synthesis procedure, structure and electrochemical performance are discussed with a special focus on the role of graphene. Finally, the outlook and remaining challenges are presented with some constructive guidelines for future research. Full article

(This article belongs to the Special Issue Chemistry of 2D Materials)

► Show Figures

Figure 1

Open AccessArticle

A Family of Externally-Functionalised Coordination Cages

Garrett D. Jackson

Max B. Tipping

Christopher G. P. Taylor

and

Chemistry 2021, 3(4), 1203-1214; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040088 - 14 Oct 2021

Abstract

New synthetic routes are presented to derivatives of a (known) M₈L₁₂ cubic coordination cage in which a range of different substituents are attached at the C⁴ position of the pyridyl rings at either end of the bis(pyrazolyl-pyridine) bridging ligands. The substituents are (i) –CN groups (new ligand L^CN), (ii) –CH₂OCH₂–CCH (containing a terminal alkyne) groups (new ligand L^CC); and (iii) –(CH₂OCH₂)₃CH₂OMe (tri-ethyleneglycol monomethyl ether) groups (new ligand L^PEG). The resulting functionalised ligands combine with M²⁺ ions (particularly Co²⁺, Ni²⁺, Cd²⁺) to give isostructural [M₈L₁₂]¹⁶⁺ cage cores bearing 24 external functional groups; the cages based on L^CN (with M²⁺ = Cd²⁺) and L^CC (with M²⁺ = Ni²⁺) have been crystallographically characterised. The value of these is twofold: (i) exterior nitrile or alkene substituents can provide a basis for further synthetic opportunities via ‘Click’ reactions allowing in principle a diverse range of functionalisation of the cage exterior surface; (ii) the exterior –(CH₂OCH₂)₃CH₂OMe groups substantially increase cage solubility in both water and in organic solvents, allowing binding constants of cavity-binding guests to be measured under an increased range of conditions. Full article

(This article belongs to the Special Issue Metal-Organic Cages and Their Applications)

► Show Figures

Graphical abstract

Open AccessArticle

Dehydration of Fructose to 5-Hydroxymethylfurfural: Effects of Acidity and Porosity of Different Catalysts in the Conversion, Selectivity, and Yield

João Pedro Vieira Lima

Pablo Teles Aragão Campos

and

Chemistry 2021, 3(4), 1189-1202; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040087 - 12 Oct 2021

Abstract

There is a demand for renewable resources, such as biomass, to produce compounds considered as platform molecules. This study deals with dehydration of fructose for the formation of 5-hydroxymethylfurfural (HMF), a feedstock molecule. Different catalysts (aluminosilicates, niobic acid, 12-tungstophosphoric acid—HPW, and supported HPW/Niobia) were studied for this reaction in an aqueous medium. The catalysts were characterized by XRD, FT-IR, N₂ sorption at −196 °C and pyridine adsorption. It was evident that the nature of the sites (Brønsted and Lewis), strength, quantity and accessibility to the acidic sites are critical to the conversion and yield results. A synergic effect of acidity and mesoporous area are key factors affecting the activity and selectivity of the solid acids. Niobic acid (Nb₂O₅·nH₂O) revealed the best efficiency (highest TON, yield, selectivity and conversion). It was determined that the optimum acidity strength of catalysts should be between 80 to 100 kJ mol⁻¹, with about 0.20 to 0.30 mmol g⁻¹ of acid sites, density about 1 site nm⁻² and mesoporous area about 100 m² g⁻¹. These values fit well within the general order of the observed selectivity (i.e., Nb₂O₅ > HZSM-5 > 20%HPW/Nb₂O₅ > SiO₂-Al₂O₃ > HY > HBEA). Full article

(This article belongs to the Section Catalysis)

► Show Figures

Graphical abstract

Open AccessArticle

Evaluation of the Anticancer and DNA-Binding Characteristics of Dichloro(diimine)zinc(II) Complexes

and

Chemistry 2021, 3(4), 1178-1188; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040086 - 11 Oct 2021

Abstract

Several metal diimine complexes have been reported to possess anticancer properties. To evaluate the anticancer properties of tetrahedral zinc(II) diimine complexes, six complexes were synthesized with the general formula M(N^N)Cl₂ {where M = Zn, Pt and N^N = 2,2’-biquinoline (1), 2,2’-dipyridylketone (2) and 4-((pyridine-2-ylmethylene)amino)phenol (3)}. In general, the intrinsic DNA-binding constants for the different compounds exhibited values within close proximity; the changes in the viscosity of the CT-DNA upon binding to the compounds suggest intercalation-binding mode. Molecular docking study predicted that complexes containing the highly planar ligand 2,2’-biquinoline are capable to establish π–π interactions with nucleobases of the DNA; the other four complexes engaged in donor–acceptor interactions with DNA nucleobases. The six complexes and two reference drugs (cisplatin and sunitinib) were tested against two cancer cell lines (COLO 205 and RCC-PR) and one normal cell line (LLC-MK2), highlighting the better performance of the zinc(II) complexes compared to their platinum(II) analogues. Moreover, zinc(II) complexes have higher selectivity index values than the reference drugs, with promising anticancer properties. Full article

(This article belongs to the Section Bioinorganics)

► Show Figures

Graphical abstract

Open AccessArticle

Novel Approaches for Biocorrosion Mitigation in Sewer Systems

Georgios Fytianos

Dimitra Banti

Esmeralda Dushku

Efthimios Papastergiadis

Minas Yiangou

and

Petros Samaras

Chemistry 2021, 3(4), 1166-1177; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040085 - 09 Oct 2021

Abstract

Concrete sewer pipes can be corroded by the biogenic sulfuric acid (H₂SO₄) generated from microbiological activities in a process called biocorrosion or microbiologically induced corrosion (MIC). In this study, inhibitors that can reduce Acidithiobacillus thiooxidans growth and thus may reduce the accumulation of biofilm components responsible for the biodegradation of concrete were used. D-tyrosine, tetrakis hydroxymethyl phosphonium sulfate (THPS) and TiO₂ nanoparticles were investigated as potential inhibitors of sulfur-oxidizing bacteria (SOB) growth. Results showed that most of the chemicals used can inhibit SOB growth at a concentration lower than 100 mg/L. TiO₂ nanoparticles exhibited the highest biocide effect and potential biocorrosion mitigation activity, followed by D-tyrosine and THPS. Full article

(This article belongs to the Special Issue Low-Cost Water Treatment - New Materials and New Approaches)

Open AccessArticle

Exploiting In-Situ Characterization for a Sabatier Reaction to Reveal Catalytic Details

and

Chemistry 2021, 3(4), 1157-1165; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040084 - 08 Oct 2021

Abstract

In situ characterization of catalysts provides important information on the catalyst and the understanding of its activity and selectivity for a specific reaction. TPX techniques for catalyst characterization reveal the role of the support on the stabilization and dispersion of the active sites. However, these can be altered at high temperature since sintering of active species can occur as well as possible carbon deposition through the Bosch reaction, which hinders the active species and deactivates the catalyst. In situ characterization of the spent catalyst, however, may expose the causes for catalyst deactivation. For example, a simple TPO analysis on the spent catalyst may produce CO and CO₂ via a reaction with O₂ at high temperature and this is a strong indication that deactivation may be due to the deposition of carbon during the Sabatier reaction. Other TPX techniques such as TPR and pulse chemisorption are also valuable techniques when they are applied in situ to the fresh catalyst and then to the catalyst upon deactivation. Full article

(This article belongs to the Section Catalysis)

Open AccessArticle

Partitioning Hückel–London Currents into Cycle Contributions

Wendy Myrvold

Patrick W. Fowler

and

Joseph Clarke

Chemistry 2021, 3(4), 1138-1156; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040083 - 08 Oct 2021

Abstract

Ring-current maps give a direct pictorial representation of molecular aromaticity. They can be computed at levels ranging from empirical to full ab initio and DFT. For benzenoid hydrocarbons, Hückel–London (HL) theory gives a remarkably good qualitative picture of overall current patterns, and a useful basis for their interpretation. This paper describes an implemention of Aihara’s algorithm for computing HL currents for a benzenoid (for example) by partitioning total current into its constituent cycle currents. The Aihara approach can be used as an alternative way of calculating Hückel–London current maps, but more significantly as a tool for analysing other empirical models of induced current based on conjugated circuits. We outline an application where examination of cycle contributions to HL total current led to a simple graph-theoretical approach for cycle currents, which gives a better approximation to the HL currents for Kekulean benzenoids than any of the existing conjugated-circuit models, and unlike these models it also gives predictions of the HL currents in non-Kekulean benzenoids that are of similar quality. Full article

(This article belongs to the Special Issue Current Density and Spectroscopy—A Themed Issue in Honor of Professor Riccardo Zanasi on the Occasion of His 70th Birthday)

► Show Figures

Figure 1

Open AccessArticle

Q-Tube®-Assisted Alkylation and Arylation of Xanthines and Other N-H-Containing Heterocycles in Water

Francesca Giulia Nacca

Eder J. Lenardao

Luca Sancineto

and

Claudio Santi

Chemistry 2021, 3(4), 1126-1137; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040082 - 01 Oct 2021

Abstract

In this paper, a simple and clean process for the alkylation and arylation of nitrogen-containing heterocycles is reported. The reactions were conducted using the Q-tube® as a non-conventional technology, in water as a green solvent, at overboiling temperature. The developed strategy was used to improve two steps in the total synthesis of caffeine, as reported by Narayan, and then extended to the preparation of N-decorated xanthines. Finally, piperidine, methyl piperazine, and isatine were proven to be suitable substrates for the protocol proposed herein. Full article

(This article belongs to the Special Issue Feature Paper from Top Italian Scientist)

► Show Figures

Scheme 1

Open AccessArticle

Study on Adsorption Performance of Benzoic Acid in Cyclocarya paliurus Extract by Ethyl Cellulose Microspheres

and

Chemistry 2021, 3(4), 1113-1125; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040081 - 01 Oct 2021

Abstract

Polymer microspheres with inter-connecting pores are widely used as microsphere materials. In the study, the ethyl cellulose microspheres (ECM) were prepared by using the solvent-evaporation method. Based on that, a method for the separation and purification of benzoic acid from crude extract of Cyclocarya paliurus was established by the ECM and high performance liquid chromatography (HPLC). The ECM after the sorption equilibrium was desorbed by using 40% methanol as the analytical solvent. The content of benzoic acid in eluent is up to 0.0216 mg/mL, and the benzoic acid can be obtained with a high purity of 82.22%. Furthermore, the adsorption-desorption behavior of benzoic acid onto ECM was investigated. The results of adsorption kinetics of benzoic acid showed that the adsorption followed the pseudo-first-order kinetic model. The ECM was characterized by using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and X-ray diffraction (XRD). The results showed that the ECM has a high adsorption property due to its more porous structure, phenolic hydroxyl group, and other oxygen-containing functional groups. This method and the ECM can be used stably, continuously, and efficiently to purify the benzoic acid from the methanol extract of C. paliurus on a large scale. Full article

(This article belongs to the Special Issue Discovery of Bioactive Ingredients from Natural Products)

Open AccessArticle

Analysis of Local and Global Aromaticity in Si₃C₅ and Si₄C₈ Clusters. Aromatic Species Containing Planar Tetracoordinate Carbon

Juan J. Torres-Vega

Diego R. Alcoba

Ofelia B. Oña

Alejandro Vásquez-Espinal

and

Chemistry 2021, 3(4), 1101-1112; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3040080 - 25 Sep 2021

Abstract

The minimum energy structures of the Si₃C₅ and Si₄C₈ clusters are planar and contain planar tetracoordinate carbons (ptCs). These species have been classified, qualitatively, as global (π) and local (σ) aromatics according to the adaptive natural density partitioning (AdNDP) method, which is an orbital localization method. This work evaluates these species’ aromaticity, focusing on confirming and quantifying their global and local aromatic character. For this purpose, we use an orbital localization method based on the partitioning of the molecular space according to the topology of the electronic localization function (LOC-ELF). In addition, the magnetically induced current density is analyzed. The LOC-ELF-based analysis coincides with the AdNDP study (double aromaticity, global, and local). Moreover, the current density analysis detects global and local ring currents. The strength of the global and local current circuit is significant, involving 4n + 2 π- and σ-electrons, respectively. The latter implicates the Si-ptC-Si fragment, which would be related to the 3c-2e σ-bond detected by the orbital localization methods in this fragment. Full article

(This article belongs to the Special Issue Current Density and Spectroscopy—A Themed Issue in Honor of Professor Riccardo Zanasi on the Occasion of His 70th Birthday)

► Show Figures

Graphical abstract

Open AccessCommunication

Chirality Transfer in a Calixarene-Based Directional Pseudorotaxane Complex

and

Chemistry 2021, 3(3), 1089-1100; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030079 - 18 Sep 2021

Abstract

Hexamethoxycalix[6]arene 3 forms a directional pseudorotaxane complex with the chiral axle (S)-(α-methyl-benzyl)benzylammonium 2⁺. Between the two (endo-chiral)-2⁺@3 and (exo-chiral)-2⁺@3 pseudorotaxane stereoisomers, the former is preferentially formed. This result confirms the validity of the “endo-α-methyl-benzyl rule”, previously reported by us. DFT calculations suggest that C-H … π interactions between the methyl group of 2⁺ and the calixarene aromatic rings, determine the stereoselectivity of the threading process toward the “endo-α-methyl-benzyl preference”. An amplification of optical rotation is observed upon formation of the pseudorotaxane complex (endo-chiral)-2⁺@3 with respect to free axle 2⁺. Thus, the specifical rotation of the 1:1 mixture of chiral 2⁺·B(ArF)₄⁻ salt and achiral 3 was augmented upon formation of the pseudorotaxane and DFT calculations were used to rationalize this result. Full article

(This article belongs to the Special Issue Current Density and Spectroscopy—A Themed Issue in Honor of Professor Riccardo Zanasi on the Occasion of His 70th Birthday)

► Show Figures

Graphical abstract

Open AccessArticle

Absorption and Isomerization of Azobenzene Guest Molecules in Polymeric Nanoporous Crystalline Phases

and

Chemistry 2021, 3(3), 1074-1088; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030078 - 16 Sep 2021

Abstract

PPO co-crystalline (CC) films including azobenzene guest molecules have been prepared and characterized by WAXD, FTIR and UV-Visible measurements. Isomerization reactions of azobenzene (photo-induced trans to cis and spontaneous cis to trans) included in α and β nanoporous-crystalline (NC) phases leading to CC phases, or simply absorbed in amorphous phase have been studied on thick and thin films. Spectroscopic analysis shows that photo-isomerization of azobenzene occurs without expulsion of azobenzene guest molecules from crystalline phases. Sorption studies of α and β NC films immersed into photo-isomerized azobenzene solution reveal a higher selectivity of the β NC phase toward cis azobenzene isomer than the α NC phase, inducing us to propose the β NC phase as particularly suitable for absorbing spherically bulky guest molecules. Full article

(This article belongs to the Special Issue Current Density and Spectroscopy—A Themed Issue in Honor of Professor Riccardo Zanasi on the Occasion of His 70th Birthday)

► Show Figures

Figure 1

Open AccessArticle

The B₂ Structural Motif as a Tool for Modulating Ring Currents in Monocyclic Li Clusters

Slađana Đorđević

and

Slavko Radenković

Chemistry 2021, 3(3), 1063-1073; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030077 - 14 Sep 2021

Abstract

Magnetically induced current densities, calculated at the M06-2X/def2-TZVP level using the diamagnetic-zero version of the continuous transformation of origin of current density (CTOCD-DZ) method, were employed to study the aromaticity in

{Li}_{3} B_{2}^{-}

and

{Li}_{4} B_{2}

. It [...] Read more.

{Li}_{3} B_{2}^{-}

and

{Li}_{4} B_{2}

. It was found that the

{Li}_{3} / {Li}_{4}

rings in

{Li}_{3} B_{2}^{-}

and

{Li}_{4} B_{2}

remarkably resemble the monocyclic

{Li}_{3}^{+}

and

{Li}_{4}^{2 +}

clusters. Unlike the parent

{Li}_{3}^{+}

and

{Li}_{4}^{2 +}

systems that sustain negligibly weak global current density circulation, the

{Li}_{3} B_{2}^{-}

and

{Li}_{4} B_{2}

clusters exhibit a strong diatropic current density. The present work demonstrates how structural modifications introduced by the

B_{2}

unit can be used for modulating the current density in cyclic Li-based clusters. Full article

(This article belongs to the Special Issue Current Density and Spectroscopy—A Themed Issue in Honor of Professor Riccardo Zanasi on the Occasion of His 70th Birthday)

► Show Figures

Graphical abstract

Open AccessCommunication

Spectroscopic Evidence of New Low-Dimensional Planar Carbon Allotropes Based on Biphenylene via On-Surface Ullmann Coupling

Iulia Emilia Brumboiu

and

Chemistry 2021, 3(3), 1057-1062; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030076 - 13 Sep 2021

Abstract

The bottom-up synthesis and preliminary characterizations of a new biphenylene-based 2D framework are presented. This new low-dimensional carbon allotrope potentially completes the many hypothesized carbon networks based on biphenylene. Full article

(This article belongs to the Special Issue On-Surface Synthesis: Methods and Applications)

► Show Figures

Graphical abstract

Open AccessArticle

The Non-Anhydrous, Minimally Basic Synthesis of the Dopamine D₂ Agonist [¹⁸F]MCL-524

and

Chemistry 2021, 3(3), 1047-1056; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030075 - 09 Sep 2021

Abstract

The dopamine D₂ agonist MCL-524 is selective for the D₂ receptor in the high-affinity state (D₂^high), and, therefore, the PET analogue, [¹⁸F]MCL-524, may facilitate the elucidation of the role of D₂^high in disorders such as schizophrenia. However, the previously reported synthesis of [¹⁸F]MCL-524 proved difficult to replicate and was lacking experimental details. We therefore developed a new synthesis of [¹⁸F]MCL-524 using a “non-anhydrous, minimally basic” (NAMB) approach. In this method, [¹⁸F]F⁻ is eluted from a small (10–12 mg) trap-and-release column with tetraethylammonium tosylate (2.37 mg) in 7:3 MeCN:H₂O (0.1 mL), rather than the basic carbonate or bicarbonate solution that is most often used for [¹⁸F]F⁻ recovery. The tosylated precursor (1 mg) in 0.9 mL anhydrous acetonitrile was added directly to the eluate, without azeotropic drying, and the solution was heated (150 °C/15 min). The catechol was then deprotected with the Lewis acid In(OTf)₃ (10 equiv.; 150 °C/20 min). In contrast to deprotection with protic acids, Lewis-acid-based deprotection facilitated the efficient removal of byproducts by HPLC and eliminated the need for SPE extraction prior to HPLC purification. Using the NAMB approach, [¹⁸F]MCL-524 was obtained in 5–9% RCY (decay-corrected, n = 3), confirming the utility of this improved method for the multistep synthesis of [¹⁸F]MCL-524 and suggesting that it may applicable to the synthesis of other ¹⁸F-labeled radiotracers. Full article

(This article belongs to the Section Radiochemistry)

► Show Figures

Graphical abstract

Open AccessArticle

Yb to Tb Cooperative Upconversion in Supramolecularly Assembled Complexes in a Solution

and

Chemistry 2021, 3(3), 1037-1046; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030074 - 06 Sep 2021

Abstract

The podand-type ligand L, based on a tertiary amine substituted by three pyridyl-6-phosphonic acid functions, forms hydrated complexes with Ln³⁺ cations. The luminescence properties of the YbL complex were studied in D₂O as a function of the pD and temperature. In basic conditions, increases in the luminescence quantum yield and the excited state lifetime of the Yb centered emission associated with the ²F_5/2 → ²F_7/2 transition were observed and attributed to a change in the hydration number from two water molecules in the first coordination sphere of Yb at acidic pH to a single one in basic conditions. Upon the addition of TbCl₃ salts to a solution containing the YbL complex in D₂O, heteropolynuclear Yb/Tb species formed, and excitation of the Yb at 980 nm resulted in the observation of the typical visible emission of Tb as a result of a cooperative upconversion (UC) photosensitization process. The UC was further evidenced by the quadratic dependence of the UC emission as a function of the laser power density. Full article

(This article belongs to the Special Issue Molecular and Supramolecular Upconversion)

► Show Figures

Figure 1

Open AccessFeature PaperArticle

Electronic Currents and Anapolar Response Induced in Molecules by Monochromatic Light

Francesco Ferdinando Summa

and

Paolo Lazzeretti

Chemistry 2021, 3(3), 1022-1036; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030073 - 05 Sep 2021

Abstract

It is shown that the electric dipole- and electric quadrupole–anapole polarizabilities, denoted respectively by

f_{α β}^{'}

and

g_{α, β γ}^{'}

, and the anapole magnetizability

a_{α β}

, are intrinsic properties of the electron cloud of molecules [...] Read more.

It is shown that the electric dipole- and electric quadrupole–anapole polarizabilities, denoted respectively by

f_{α β}^{'}

and

g_{α, β γ}^{'}

, and the anapole magnetizability

a_{α β}

, are intrinsic properties of the electron cloud of molecules responding to optical fields.

f_{α β}^{'}

is a nonvanishing property of chiral and achiral compounds, whereas

a_{α β}

is suitable for enantiomer discrimination of chiral species. They can conveniently be evaluated by numerical integration, employing a formulation complementary to that provided by perturbation theory and relying on the preliminary computation of electronic current density tensors all over the molecular domain. The origin dependence of the dynamic anapolar response is rationalized via related computational techniques employing numerical integration, as well as definitions of molecular property tensors, for example, electric dipole and electric quadrupole polarizabilties and magnetizability. A preliminary application of the theory is reported for the

R_{a}

enantiomer of the hydrogen peroxide molecule, evaluating tensor components of electric dipole-anapole polarizability and anapole magnetizability as functions of the dihedral angle

ϕ \equiv ∠

H-O-O-H in the range

0^{\circ} \leq ϕ \leq 180^{\circ}

. Full article

(This article belongs to the Special Issue Current Density and Spectroscopy—A Themed Issue in Honor of Professor Riccardo Zanasi on the Occasion of His 70th Birthday)

► Show Figures

Figure 1

Open AccessArticle

Spatial Contributions to ¹H NMR Chemical Shifts of Free-Base Porphyrinoids

and

Chemistry 2021, 3(3), 1005-1021; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030072 - 05 Sep 2021

Abstract

A recently developed methodology for calculating, analyzing, and visualizing nuclear magnetic shielding densities is used for studying spatial contributions including ring-current contributions to

^{1}

H nuclear magnetic resonance (NMR) chemical shifts of aromatic and anti-aromatic free-base porphyrinoids. Our approach allows a visual inspection [...] Read more.

A recently developed methodology for calculating, analyzing, and visualizing nuclear magnetic shielding densities is used for studying spatial contributions including ring-current contributions to

^{1}

H nuclear magnetic resonance (NMR) chemical shifts of aromatic and anti-aromatic free-base porphyrinoids. Our approach allows a visual inspection of the spatial origin of the positive (shielding) and negative (deshielding) contributions to the nuclear magnetic shielding constants. Diatropic and paratropic current-density fluxes yield both shielding and deshielding contributions implying that not merely the tropicity of the current density determines whether the contribution has a shielding or deshielding character. Instead the shielding or deshielding contribution is determined by the direction of the current-density flux with respect to the studied nucleus. Full article

(This article belongs to the Special Issue Current Density and Spectroscopy—A Themed Issue in Honor of Professor Riccardo Zanasi on the Occasion of His 70th Birthday)

► Show Figures

Graphical abstract

Open AccessArticle

Magnetic Aromaticity of Cycloporphyrin Nanorings

Alessandro Landi

Francesco Ferdinando Summa

and

Guglielmo Monaco

Chemistry 2021, 3(3), 991-1004; https://0-doi-org.brum.beds.ac.uk/10.3390/chemistry3030071 - 02 Sep 2021

Abstract

The ascertainment of magnetic aromaticity is not necessarily straightforward, especially for large and bent systems, such as the cycloporphyrin nanorings recently synthesized by the group of Anderson. Six of these cycloporphyrin nanorings were studied here computationally. Indirect methods, based on nuclear shielding and magnetizabilities, and direct methods, based on standard quantum mechanics, were both used effectively to determine their magnetically induced current strength, which mostly confirmed Anderson’s classification. However, in the case of hexanions, and in particular for cyclohexaporphyrin hexacations, a significant cancellation of delocalized diatropic and paratropic flow occurred, showing that the resultant faint aromatic character was a result of competing aromatic and antiaromatic contributions, as also evidenced by the ipsocentric method. A warning is renewed on the use of isotropic shielding to determine the tropicity of the magnetically induced current. Full article

(This article belongs to the Special Issue Current Density and Spectroscopy—A Themed Issue in Honor of Professor Riccardo Zanasi on the Occasion of His 70th Birthday)

► Show Figures