Noble Gas Bonding Interactions Involving Xenon Oxides and Fluorides

Noble gas (or aerogen) bond (NgB) can be outlined as the attractive interaction between an electron-rich atom or group of atoms and any element of Group-18 acting as an electron acceptor. The IUPAC already recommended systematic nomenclature for the interactions of groups 17 and 16 (halogen and chalcogen bonds, respectively). Investigations dealing with noncovalent interactions involving main group elements (acting as Lewis acids) have rapidly grown in recent years. They are becoming acting players in essential fields such as crystal engineering, supramolecular chemistry, and catalysis. For obvious reasons, the works devoted to the study of noncovalent Ng-bonding interactions are significantly less abundant than halogen, chalcogen, pnictogen, and tetrel bonding. Nevertheless, in this short review, relevant theoretical and experimental investigations on noncovalent interactions involving Xenon are emphasized. Several theoretical works have described the physical nature of NgB and their interplay with other noncovalent interactions, which are discussed herein. Moreover, exploring the Cambridge Structural Database (CSD) and Inorganic Crystal Structure Database (ICSD), it is demonstrated that NgB interactions are crucial in governing the X-ray packing of xenon derivatives. Concretely, special attention is given to xenon fluorides and xenon oxides, since they exhibit a strong tendency to establish NgBs.

Not Only Hydrogen Bonds: Other Noncovalent Interactions

In this review, we provide a consistent description of noncovalent interactions, covering most groups of the Periodic Table. Different types of bonds are discussed using their trivial names. Moreover, the new name “Spodium bonds” is proposed for group 12 since noncovalent interactions involving this group of elements as electron acceptors have not yet been named. Excluding hydrogen bonds, the following noncovalent interactions will be discussed: alkali, alkaline earth, regium, spodium, triel, tetrel, pnictogen, chalcogen, halogen, and aerogen, which almost covers the Periodic Table entirely. Other interactions, such as orthogonal interactions and π-π stacking, will also be considered. Research and applications of σ-hole and π-hole interactions involving the p-block element is growing exponentially. The important applications include supramolecular chemistry, crystal engineering, catalysis, enzymatic chemistry molecular machines, membrane ion transport, etc. Despite the fact that this review is not intended to be comprehensive, a number of representative works for each type of interaction is provided. The possibility of modeling the dissociation energies of the complexes using different models (HSAB, ECW, Alkorta-Legon) was analyzed. Finally, the extension of Cahn-Ingold-Prelog priority rules to noncovalent is proposed.

Double Chalcogen Bonds: Crystal Engineering Stratagems via Diffraction and Multinuclear Solid-State Magnetic Resonance Spectroscopy

Group 16 chalcogens potentially provide Lewis-acidic σ-holes, which are able to form attractive supramolecular interactions with electron rich partners through chalcogen bonds. Here, a multifaceted experimental and computational study of a large series of novel chalcogen-bonded cocrystals, prepared using the principles of crystal engineering, is presented. Single-crystal X-ray diffraction studies reveal that dicyanoselenadiazole and dicyanotelluradiazole derivatives work as promising supramolecular synthons with the ability to form double chalcogen bonds with a wide range of electron donors including halides and oxygen- and nitrogen-containing heterocycles. Extensive ⁷⁷ Se and ¹²⁵ Te solid-state nuclear magnetic resonance spectroscopic investigations of cocrystals establish correlations between the NMR parameters of selenium and tellurium and the local chalcogen bonding geometry. The relationships between the electronic environment of the chalcogen bond and the ⁷⁷ Se and ¹²⁵ Te chemical shift tensors were elucidated through a natural localized molecular orbital density functional theory analysis. This systematic study of chalcogen-bond-based crystal engineering lays the foundations for the preparation of the various multicomponent systems and establishes solid-state NMR protocols to detect these interactions in powdered materials.

Direct investigation of chalcogen bonds by multinuclear solid-state magnetic resonance and vibrational spectroscopy

We report a multifaceted experimental and computational study of three self-complementary chalcogen-bond donors as well as a series of seven chalcogen bonded cocrystals.

Lead(ii) coordination polymers driven by pyridine-hydrazine donors: from anion-guided self-assembly to structural features

This work unveils an indispensable role of London dispersion forces and relativistic effects in tetrel and covalent bonds of the type Pb–X (X = O, N, S, I), which drives formation of extended architectures of lead(ii) coordination polymers.

Qualitative as well as quantitative analysis of interactions present in chlorine and bromine substituted aromatic organic crystals: A DFT linked Crystal Explorer study

The effect of noncovalent interactions in shaping a crystal structure is explored qualitatively as well as quantitatively in a DFT linked Crystal Explorer (CE) study of nine different Chlorine and Bromine substituted benzene derivatives. The qualitative approach to analyze interactions is based on Hirshfeld surface that locates electronic charge distribution on the surface, quantitative estimation is obtained by linking DFT computations withCE.In the halogen substituted benzene derivatives considered here, in addition to conventional hydrogen and halogen bonding other interactions such as those between Chlorine-Hydrogen, Bromine-Hydrogen, Bromine-Oxygen have been deciphered. The molecular crystal structure of a variety of halogen substituted aromatic molecules has been rationalized and attributed to specific interactions.

Nitropyridine-1-Oxides as Excellent π-Hole Donors: Interplay between σ-Hole (Halogen, Hydrogen, Triel, and Coordination Bonds) and π-Hole Interactions

In this manuscript, we use the primary source of geometrical information, i.e., Cambridge Structural Database (CSD), combined with density functional theory (DFT) calculations (PBE0-D3/def2-TZVP level of theory) to demonstrate the relevance of π-hole interactions in para-nitro substituted pyridine-1-oxides. More importantly, we show that the molecular electrostatic potential (MEP) value above and below the π–hole of the nitro group is largely influenced by the participation of the N-oxide group in several interactions like hydrogen-bonding (HB) halogen-bonding (XB), triel bonding (TrB), and finally, coordination-bonding (CB) (N⁺–O⁻ coordinated to a transition metal). The CSD search discloses that p-nitro-pyridine-1-oxide derivatives have a strong propensity to participate in π-hole interactions via the nitro group and, concurrently, N-oxide group participates in a series of interactions as electron donor. Remarkably, the DFT calculations show from strong to moderate cooperativity effects between π–hole and HB/XB/TrB/CB interactions (σ-bonding). The synergistic effects between π-hole and σ-hole bonding interactions are studied in terms of cooperativity energies, using MEP surface analysis and the Bader’s quantum theory of atoms in molecules (QTAIM).

Single-Crystal NMR Characterization of Halogen Bonds

Oxygen-17-enriched triphenylphosphine oxide and three of its halogen-bonded cocrystals featuring 1,4-diiodotetrafluorobenzene and 1,3,5-trifluoro-2,4,6-triiodobenzene as halogen bond donors have been characterized by ³¹P and ¹⁷O single-crystal NMR spectroscopy. Single-crystal NMR allows for the measurement of not only the magnitudes of various NMR interaction tensors, but also their orientations relative to the crystal lattice and therefore relative to the halogen bonds themselves. ³¹P chemical shift tensors, ¹⁷O chemical shift tensors, ¹⁷O quadrupolar coupling tensors, and ³¹P-¹⁷O indirect nuclear spin-spin (J) coupling tensors are reported here for P═O···I halogen bonds. The angular deviations in the directions of the pseudo-unique components of the ³¹P chemical shift tensors, the ¹⁷O chemical shift tensors, and the ¹⁷O quadrupolar coupling tensors from the direction of the oxygen-iodine halogen bond correlate with the deviations in linearity of the P═O···I halogen bond. There is also a clear decrease in anisotropy and an increase in asymmetry of the J(³¹P,¹⁷O) coupling tensors attributable to the formation of iodine-oxygen halogen bonds. The small but quantifiable changes in the tensors are consistent with the weak nature of these halogen bonds relative to the P═O motif. Overall, this work establishes single-crystal NMR as a novel probe of halogen bonds in solids. Analysis of the results has provided insights into the correlations between the magnitude and orientation of various NMR interaction tensors and the local geometry of the halogen bond. Gauge-including projector-augmented wave computations corroborate the experimental findings.

121/123Sb Nuclear Quadrupole Resonance Spectroscopy: Characterization of Non-Covalent Pnictogen Bonds and NQR Crystallography

Pnictogen (or pnicogen) bonding is an attractive interaction between the electrophilic region of group 15 elements (N, P, As, Sb, Bi) and a nucleophile. This interaction for which unique applications in catalysis have recently been uncovered continues to gain popularity. Here, we investigate a series of pnictogen-bonded cocrystals based on SbF₃ and SbCl₃, prepared via mechanochemical ball milling, with ^121/123Sb ( I = ⁵/₂ and ⁷/₂, respectively) nuclear quadrupole resonance (NQR) spectroscopy. Observed NQR frequency shifts upon cocrystallization are on the order of 0.1 to 10 MHz and are clearly diagnostic of the formation of pnictogen bonds to antimony. Further evidence for pnictogen bonding is obtained by complementary ¹³C cross-polarization magic-angle spinning solid-state NMR experiments. DFT calculations of NMR parameters as well as natural localized molecular orbital analyses support the experimental findings and elucidate the electronic origins of the experimental NQR frequency shifts. This work provides insights into the changes in the antimony quadrupolar coupling constant upon pnictogen bonding: strikingly, the decreases noted here parallel those known for hydrogen bonds, but contrast with the increases reported for halogen bonds. The utility of the observed antimony nuclear quadrupolar coupling constants in constraining structural models of cocrystals for which diffraction-based structures are unavailable, i.e., a rudimentary implementation of NQR crystallography, is established. Overall, this work offers a new approach to understand emerging classes of electrophilic interactions and to contextualize them in the broader landscape of established chemical bonding paradigms.

Unexpected chalcogen bonds in tetravalent sulfur compounds

Combined CSD analysis and theoretical calculations show the importance of the polarizability in chalcogen bonding interactions. We provide evidence that the Lewis base has a preference in some cases for the σ-hole that is opposite to the more polarizable group instead of the more electron withdrawing one.

S⋅⋅⋅Sn Tetrel Bonds in the Activation of Peroxisome Proliferator-Activated Receptors (PPARs) by Organotin Molecules

In this study, a PDB (Protein Data Bank) analysis and theoretical calculations (PBE0-D3/def2-TZVP level of theory) were combined to analyze the impact of S⋅⋅⋅Sn tetrel-bonding interactions in the activation mechanism of peroxisome proliferator-activated receptors (PPARs) by two organotin derivatives, triphenyltin (TPT) and tributyltin (TBT). The presence of a covalently bonded CYS285 to the organotin molecule was found to be key to enhance the σ-hole-donor ability of the tin atom, thus strengthening the tetrel-bonding interaction with a sulfur atom belonging to a vicinal methionine residue (MET364).

Tetrel Bonding Interactions in Perchlorinated Cyclopenta- and Cyclohexatetrelanes: A Combined DFT and CSD Study

In this manuscript, we combined DFT calculations (PBE0-D3/def2-TZVP level of theory) and a Cambridge Structural Database (CSD) survey to evaluate the ability of perchlorinated cyclopenta- and cyclohexatetrelanes in establishing tetrel bonding interactions. For this purpose, we used Tr₅Cl₁₀ and Tr₆Cl₁₂ (Tr = Si and Ge) and HCN, HF, OH⁻ and Cl⁻ as electron donor entities. Furthermore, we performed an Atoms in Molecules (AIM) analysis to further describe and characterize the interactions studied herein. A survey of crystal structures in the CSD reveals that close contacts between Si and lone-pair-possessing atoms are quite common and oriented along the extension of the covalent bond formed by the silicon with the halogen atom.

A theoretical study of perovskites related to CH3NH3PbX3(X = F, Cl, Br, I)

MAPIand related perovskites have been studied using a hybrid DFT/HF DFT method with a simplified “corner” model. Bond dissociation energies and¹H,¹³C,¹⁵N and²⁰⁷Pb absolute shieldings were calculated.