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Crystals
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σ- and π-Hole Interactions (Volume II)
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σ- and π-Hole Interactions (Volume II)

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 15692

Special Issue Editor

Prof. Dr. Antonio Frontera

E-Mail Website
Guest Editor
Department de Química, Universitat de les Illes Balears, Palma de Mallorca, 07122 Baleares, Spain
Interests: noncovalent interactions; theoretical chemistry; DFT calculations; σ- and π-hole interactions; crystallography
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Noncovalent interactions are very important in many disciplines, especially in crystal growth and crystal engineering. Today, we know, mostly from theoreticians, that the distribution of electron density around covalently bonded atoms is anisotropic. Therefore, a single atom exhibits areas of higher and lower electron density, where electrostatic potential can be negative and positive, respectively. Consequently, the positive area (σ- or π-hole) is able to form attractive interactions with any electron-rich site. Following the emergence of the halogen bond (HaB), interest in the similar behavior of the elements of groups 11–16 and 18 from the periodic table to form analogous attractive interactions with nucleophiles has grown exponentially. It is now well recognized that HaB and chalcogen bonds (ChB) form supramolecular synthons in their solid state. However, more experimental information is likely needed in order to extend such a statement to the elements of groups 13, 14, and 15 acting as Lewis acids, and to be able to develop some general heuristic principles.

We invite researchers to contribute to the second volume of the Special Issue on σ- and π-hole interactions, which is intended to serve as a unique multidisciplinary forum covering all aspects of noncovalent interactions involving elements from groups 11 to 18 as electron acceptors in crystalline materials.

The potential topics include but are not limited to the following:

  • Synthesis and growth crystals exhibiting σ- and π-hole interactions;
  • Crystal engineering based on σ- and π-hole interactions;
  • Description, analysis, and theoretical studies of supramolecular assemblies;
  • Structure and properties of new materials based on σ- and π-hole interactions.

Prof. Dr. Antonio Frontera
Guest Editor

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. Crystals 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 2600 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

  • Halogen bonding
  • Chalcogen bonding
  • Pnicogen bonding
  • Tetrel bonding
  • Triel bonding
  • Spodium bonding
  • Regium bonding
  • σ- and π- hole interactions

Published Papers (6 papers)

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Research

12 pages, 3331 KiB  
Article
A Robust Supramolecular Heterosynthon Assembled by a Hydrogen Bond and a Chalcogen Bond
by Shaobin Miao, Yunfan Zhang, Linjie Shan, Mingyuan Xu, Jian-Ge Wang, Yu Zhang and Weizhou Wang
Crystals 2021, 11(11), 1309; https://doi.org/10.3390/cryst11111309 - 27 Oct 2021
Cited by 6 | Viewed by 1659
Abstract
The 1:1 and 2:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole have been successfully synthesized and resolved; the noncovalent interactions in the crystal structures have been studied in detail by quantum chemical calculations. In both of the crystal structures, isophthalic acid and 2,1,3-benzoselenadiazole are [...] Read more.
The 1:1 and 2:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole have been successfully synthesized and resolved; the noncovalent interactions in the crystal structures have been studied in detail by quantum chemical calculations. In both of the crystal structures, isophthalic acid and 2,1,3-benzoselenadiazole are bound together by a cyclic supramolecular heterosynthon assembled by an O–H···N hydrogen bond and a N–Se···O chalcogen bond. The crystal structures of the 1:1 and 2:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole and the crystal structure of pure isophthalic acid are very similar, which indicates that the [COOH]···[Se−N] cyclic heterosynthon can be an effective alternative to the strong [COOH]2 cyclic homosynthon. The quantum theory of atoms in molecules further recognizes the existence of the hydrogen bond and chalcogen bond. The results of quantum chemical calculations show that the strengths of the π···π stacking interactions in the 1:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole are almost the same as those in the 2:1 cocrystals of isophthalic acid and 2,1,3-benzoselenadiazole, and the strengths of the [COOH]···[Se−N] cyclic heterosynthons (about 9.00 kcal/mol) are less than the strengths of the much stronger [COOH]2 cyclic homosynthons (14.00 kcal/mol). These calculated results are in good agreement with those experimentally observed, demonstrating that, although not as strong as the [COOH]2 cyclic homosynthon, the [COOH]···[Se−N] cyclic heterosynthon can also play a key role in the crystal growth and design. Full article
(This article belongs to the Special Issue σ- and π-Hole Interactions (Volume II))
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21 pages, 5499 KiB  
Article
Synthesis and Structural Studies of Two New Anthracene Derivatives
by Rogério F. Costa, Marilene S. Oliveira, Antônio S. N. Aguiar, Jean M. F. Custodio, Paolo Di Mascio, José R. Sabino, Giuliana V. Verde, João Carlos Perbone de Souza, Lauriane G. Santin, Ademir J. Camargo, Inaya C. Barbosa, Solemar S. Oliveira and Hamilton B. Napolitano
Crystals 2021, 11(8), 934; https://doi.org/10.3390/cryst11080934 - 12 Aug 2021
Cited by 3 | Viewed by 2868
Abstract
Anthracene derivatives are an interesting class of compounds and modifications in the anthracene ring, producing different compounds with different properties. Structural analysis of anthracene derivatives with modifications in position 9,10 of the aromatic ring is necessary in order to obtain information about its [...] Read more.
Anthracene derivatives are an interesting class of compounds and modifications in the anthracene ring, producing different compounds with different properties. Structural analysis of anthracene derivatives with modifications in position 9,10 of the aromatic ring is necessary in order to obtain information about its properties. The introduction of groups with polar substituents increases the possibility to modify the molecule lipophilicity, corroborating its use as bioimaging probes. Anthracene derivatives are used in many biochemical applications. These compounds can react with molecular singlet oxygen [O2 (1Δg)], a reactive oxygen species, through the Diels–Alder reaction [4 + 2] to form the respective endoperoxide and to be used as a chemical trap in biological systems. Thus, the structural and crystalline characterizations of two anthracene derivatives are presented in this work to obtain information about their physical-chemical properties. The compounds were characterized by Fourier-transform infrared spectroscopy, thermogravimetric analyses and scanning electron microscopy. The molecular structures of the compounds were studied by the Density Functional Theory, M06-2X/6-311++G(d,p) level of theory in the gas phase. From the results obtained for the frontier molecular orbitals, HOMO and LUMO, and from the Molecular Electrostatic Potential map, it was possible to predict the chemical properties of both compounds. The supramolecular arrangements were also theoretically studied, whose molecules were kept fixed in their crystallographic positions, through the natural bonding orbitals analysis to check the stability of interactions and the quantum theory of atoms in molecules to verify the type of intermolecular interaction between their molecules, as well as how they occur. Full article
(This article belongs to the Special Issue σ- and π-Hole Interactions (Volume II))
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Graphical abstract

12 pages, 2393 KiB  
Article
The Face-to-Face σ-Hole⋯σ-Hole Stacking Interactions: Structures, Energies, and Nature
by Yu Zhang and Weizhou Wang
Crystals 2021, 11(8), 877; https://doi.org/10.3390/cryst11080877 - 28 Jul 2021
Cited by 2 | Viewed by 1382
Abstract
The existence of the π⋯π stacking interaction is well-known. Similarly, it is reasonable to assume the existence of the σ-hole⋯σ-hole stacking interaction. In this work, the structures, energies, and nature of the face-to-face σ-hole⋯σ-hole stacking interactions in the crystal structures have been investigated [...] Read more.
The existence of the π⋯π stacking interaction is well-known. Similarly, it is reasonable to assume the existence of the σ-hole⋯σ-hole stacking interaction. In this work, the structures, energies, and nature of the face-to-face σ-hole⋯σ-hole stacking interactions in the crystal structures have been investigated in detail by the quantum chemical calculations. The calculated results clearly show that the face-to-face σ-hole⋯σ-hole stacking interactions exist and have unique properties, although their strengths are not very significant. The energy component analysis reveals that, unlike many other dispersion-dominated noncovalent interactions in which the induction energies always play minor roles for their stabilities, for the face-to-face σ-hole⋯σ-hole stacking interaction the contribution of the induction energy to the total attractive energy is close to or even larger than that of the electrostatic energy. The structures, energies, and nature of the face-to-face σ-hole⋯σ-hole stacking interactions confined in small spaces have also been theoretically simulated. One of the important findings is that encapsulation of the complex bound by the face-to-face σ-hole⋯σ-hole stacking interaction can tune the electronic properties of the container. Full article
(This article belongs to the Special Issue σ- and π-Hole Interactions (Volume II))
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Graphical abstract

22 pages, 7115 KiB  
Article
Weak Interactions in Cocrystals of Isoniazid with Glycolic and Mandelic Acids
by Raquel Álvarez-Vidaurre, Alfonso Castiñeiras, Antonio Frontera, Isabel García-Santos, Diego M. Gil, Josefa M. González-Pérez, Juan Niclós-Gutiérrez and Rocío Torres-Iglesias
Crystals 2021, 11(4), 328; https://doi.org/10.3390/cryst11040328 - 25 Mar 2021
Cited by 8 | Viewed by 3047
Abstract
This work deals with the preparation of pyridine-3-carbohydrazide (isoniazid, inh) cocrystals with two α-hydroxycarboxylic acids. The interaction of glycolic acid (H2ga) or d,l-mandelic acid (H2ma) resulted in the formation of cocrystals or salts of composition (inh)·(H2ga) ( [...] Read more.
This work deals with the preparation of pyridine-3-carbohydrazide (isoniazid, inh) cocrystals with two α-hydroxycarboxylic acids. The interaction of glycolic acid (H2ga) or d,l-mandelic acid (H2ma) resulted in the formation of cocrystals or salts of composition (inh)·(H2ga) (1) and [Hinh]+[Hma]–·(H2ma) (2) when reacted with isoniazid. An N′-(propan-2-ylidene)isonicotinic hydrazide hemihydrate, (pinh)·1/2(H2O) (3), was also prepared by condensation of isoniazid with acetone in the presence of glycolic acid. These prepared compounds were well characterized by elemental analysis, and spectroscopic methods, and their three-dimensional molecular structure was determined by single crystal X-ray crystallography. Hydrogen bonds involving the carboxylic acid occur consistently with the pyridine ring N atom of the isoniazid and its derivatives. The remaining hydrogen-bonding sites on the isoniazid backbone vary based on the steric influences of the derivative group. These are contrasted in each of the molecular systems. Finally, Hirshfeld surface analysis and Density-functional theory (DFT) calculations (including NCIplot and QTAIM analyses) have been performed to further characterize and rationalize the non-covalent interactions. Full article
(This article belongs to the Special Issue σ- and π-Hole Interactions (Volume II))
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15 pages, 4052 KiB  
Article
H-Bonds, π-Stacking and (Water)O-H/π Interactions in (µ4-EDTA)Bis(Imidazole) Dicopper(II) Dihydrate
by Jeannette Carolina Belmont-Sánchez, María Eugenia García-Rubiño, Antonio Frontera, Josefa María González-Pérez, Alfonso Castiñeiras and Juan Niclós-Gutiérrez
Crystals 2021, 11(1), 48; https://doi.org/10.3390/cryst11010048 - 08 Jan 2021
Cited by 4 | Viewed by 2728
Abstract
We synthesized and studied the polymeric compound {[Cu2(µ4-EDTA)(Him)2] 2H2O}n (1). The single-crystal structure is reported along with an in depth characterization of its thermal stability (TGA), spectral properties (FT-IR, Vis-UV and RSE), [...] Read more.
We synthesized and studied the polymeric compound {[Cu2(µ4-EDTA)(Him)2] 2H2O}n (1). The single-crystal structure is reported along with an in depth characterization of its thermal stability (TGA), spectral properties (FT-IR, Vis-UV and RSE), and magnetic behavior. The crystal consists of infinite 2D-networks built by centrosymmetric dinuclear motifs, constructed by means of a bridging anti,syn-carboxylate group from each asymmetric unit. Each layer guides Him ligands toward their external faces. They are connected by intermolecular (Him)N-H···O(carboxylate) bonds and antiparallel π–π stacking between symmetry related pairs of Him ligands, and then pillared in a 3D-network with parallel channels, where disordered water molecules are guested. About half of the labile water is lost from these channels over a wide temperature range (r.t. to 210 °C) before the other one, most strongly retained by the cooperating action of (water)O1-H(1A)···O(carboxylate) and (water) O1-H(1B)···π(Him) interactions. The latter is lost when organic ligands start to burn. ESR spectra and magnetic measurements indicated that symmetry related Cu(II) centers connected by the bridging carboxylate groups behave magnetically not equivalently, enabling an exchange interaction larger than their individual Zeeman energies. Full article
(This article belongs to the Special Issue σ- and π-Hole Interactions (Volume II))
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Graphical abstract

9 pages, 16822 KiB  
Article
Sildenafil–Resorcinol Cocrystal: XRPD Structure and DFT Calculations
by Rafael Barbas, Vineet Kumar, Oriol Vallcorba, Rafel Prohens and Antonio Frontera
Crystals 2020, 10(12), 1126; https://doi.org/10.3390/cryst10121126 - 10 Dec 2020
Cited by 17 | Viewed by 3099
Abstract
Herein, the X-ray powder diffraction (XRPD) crystal structure of a new Sildenafil cocrystal is reported, where resorcinol has been used as the coformer. The crystal structure has been solved by means of direct space methods used in combination with density functional theory (DFT) [...] Read more.
Herein, the X-ray powder diffraction (XRPD) crystal structure of a new Sildenafil cocrystal is reported, where resorcinol has been used as the coformer. The crystal structure has been solved by means of direct space methods used in combination with density functional theory (DFT) calculations. In the structure, the Sildenafil and resorcinol molecules form cooperative hydrogen bond (HB) and π-stacking interactions that have been analyzed using DFT calculations, the molecular electrostatic potential (MEP) surface, and noncovalent interaction plot (NCI plot). The formation of O–H⋯N H-bonds between resorcinol and Sildenafil increases the dipole moment and enhances the antiparallel π-stacking interaction. Full article
(This article belongs to the Special Issue σ- and π-Hole Interactions (Volume II))
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