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In this study we propose to coin the term Wolfium bond (WfB) to refer to a net attractive force (noncovalent interaction) between any element of group 6 and electron donor atoms (neutral molecules or anions) and to differentiate it from a coordination bond (metal‐ligand interaction). We provide evidence of the existence of this interaction by inspecting the X‐ray crystal structure of proteins containing Molybdopterin and Tungstopterin cofactors from the Protein Data Bank (PDB). The plausible biological role of the interaction as well as its physical nature (antibonding Wf‐Ligand orbital involved) are also analyzed by means of ab initio calculations (RI‐MP2/def2‐TZVP level of theory), Atoms in Molecules (AIM), Natural Bond Orbital (NBO) and Noncovalent Interactions plot (NCIplot) analyses. [ABSTRACT FROM AUTHOR]

Studying noncanonical intermolecular interactions between a ligand and a protein constitutes an emerging research field. Identifying synthetically accessible molecular fragments that can engage in intermolecular interactions is a key objective in this area. Here, it is shown that so‐called "π‐hole interactions" are present between the nitro moiety in nitro aromatic ligands and lone pairs within protein structures (water and protein carbonyls and sulfurs). Ample structural evidence was found in a PDB analysis and computations reveal interaction energies of about −5 kcal mol−1 for ligand–protein π‐hole interactions. Several examples are highlighted for which a π‐hole interaction is implicated in the superior binding affinity or inhibition of a nitro aromatic ligand versus a similar non‐nitro analogue. The discovery that π‐hole interactions with nitro aromatics are significant within protein structures parallels the finding that halogen bonds are biologically relevant. This has implications for the interpretation of ligand–protein complexation phenomena, for example, involving the more than 50 approved drugs that contain a nitro aromatic moiety. [ABSTRACT FROM AUTHOR]

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 bonds in action: A combined Protein Data Bank and computational analysis (PBE0‐D3/def2‐TZVP) revealed the importance of S⋅⋅⋅Sn tetrel‐bonding interactions in the mechanism of activation of peroxisome proliferator‐activated receptors (PPARs) by organotin molecules. [ABSTRACT FROM AUTHOR]

The ability of metal clusters involving elements from group 11 (Ag, Cu, Au) to favorably interact with π systems of different size and electronic nature was evaluated at the PBE0‐D3/def2‐TZVPP//PBE0‐D3/def2‐TZVP level of theory. The M9 clusters (M=Cu, Ag, Au) were used as σ‐hole and σ‐lump donors, and benzene, trifluorobenzene, and hexafluorobenzene as aromatic rings. In addition, the study was expanded to the analysis of extended π systems by using naphthalene and anthracene as well as their corresponding perfluorinated derivatives. Furthermore, Bader's theory of Atoms in Molecules as well as natural bonding orbital and spin‐density calculations were used to further investigate and characterize the regium–π and σ‐lump complexes described herein. Apparently, regium–π bonds have not previously been described in the literature and may be of great importance in the understanding of organocatalytic processes involving aromatic substrates as well as in the design of new materials based on this novel subclass of σ‐hole bonding. [ABSTRACT FROM AUTHOR]

In this study, the ability of beryllium compounds to establish π-hole bonding interactions has been evaluated at the RI-MP2/def2-TZVPD level of theory. A search of the Protein Data Bank revealed some X-ray crystal structures in which BeF3− moieties act as electron-acceptor entities. We have used [Mg(BeF3)(HCOO)] ( 1) as a π-hole bond donor and CO, CH3CN, NH3, O(CH3)2, S(CH3)2, H3PO, and glycine as electron-rich entities. In all cases, favorable binding energies were obtained, reflecting the attractive nature of the interaction involving the trivalent beryllium atom (-BeF3 moiety). In addition, we have used Bader's theory of 'atoms in molecules' and noncovalent interaction (NCI) plot analysis to further investigate and characterize the π-hole complexes described herein. To the best of our knowledge, π-hole interactions involving beryllium have not hitherto been described in the literature. [ABSTRACT FROM AUTHOR]

Iridium(I) complexes with phosphine-phosphite ligands efficiently catalyze the enantioselective hydrogenation of diverse seven-membered C=N-containing heterocyclic compounds (eleven examples; up to 97 % ee). The P-OP ligand L3, which incorporates an ortho-diphenyl substituted octahydrobinol phosphite fragment, provided the highest enantioselectivities in the hydrogenation of most of the heterocyclic compounds studied. The observed stereoselection was rationalized by means of DFT calculations. [ABSTRACT FROM AUTHOR]

High-level calculations (RI-MP2/def2-TZVP) disclosed that the σ-hole in between two C atoms of cycloalkane X2CCX2 structures (X=F, CN) is increasingly exposed with decreasing ring size. The interacting energy of complexes of F−, HO−, N≡C−, and H2CO with cyclopropane and cyclobutane X2CCX2 derivatives was calculated. For X=F, these energies are small to positive, while for X=CN they are all negative, ranging from −6.8 to −42.3 kcal mol−1. These finding are corroborated by a thorough statistical survey of the Cambridge Structural Database (CSD). No clear evidence could be found in support of non-covalent carbon bonding between electron-rich atoms (El.R.) and F2CCF2 structures. In marked contrast, El.R.⋅⋅⋅(CN)2CC(CN)2 interactions are abundant and highly directional. Based on these findings, the hydrophobic electrophilic bowl formed by 1,1′,2,2′-tetracyano cyclopropane or cyclobutane derivatives is proposed as a new and synthetically accessible supramolecular synthon. [ABSTRACT FROM AUTHOR]

The glyoxylate shunt is an anaplerotic bypass of the traditional Krebs cycle. It plays a prominent role in Mycobacterium tuberculosis virulence, so it can be exploited for the development of antitubercular therapeutics. The shunt involves two enzymes: isocitrate lyase (ICL) and malate synthase (GlcB). The shunt bypasses two steps of the tricarboxylic acid cycle, allowing the incorporation of carbon, and thus, refilling oxaloacetate under carbon-limiting conditions. The targeting of ICL is complicated; however, GlcB, which accommodates the pantothenate tail of acetyl-CoA in the active site, is easier to target. A catalytic Mg2+ unit is located at the bottom of the cavity, and plays a very important role. Recently, the development of effective antituberculosis drugs based on phenyldiketo acids (PDKAs) has been reported. Interestingly, all the crystal structures of GlcB-inhibitor complexes exhibit close contact between the carboxylate of Asp633 and the face of the aromatic ring of the inhibitor. Remarkably, the replacement of the phenyl ring in PDKA by aliphatic moieties yields inactive inhibitors, suggesting that the aromatic moiety is crucial for inhibition. However, the aromatic ring of PDKA is not electron-deficient, and consequently, the anion-π interaction is expected to be very weak (dominated only by polarization effects). Herein, through a combination analysis of the recent X-ray structures of GlcB-PDKA complexes retrieved from the protein data bank (PDB) and computational ab initio studies (RI-MP2/def2-TZVP level of theory), we demonstrate the prominent role of the Mg2+ ion in the active site, which promotes long-range enhancement of the anion-π interaction. [ABSTRACT FROM AUTHOR]

The importance and functional relevance of S⋅⋅⋅Sn tetrel‐bonding interactions in the activation of peroxisome proliferator‐activated receptors (PPARs) by organotin molecules was evidenced using a combined theoretical and Protein Data Bank analysis. In the figure, three hummingbirds carrying sulfur atoms establish tetrel‐bonding interactions with the organotin molecules that hang from the tree trunk. These molecules are anchored to the protein through the establishment of covalent S−Sn bonds. More information can be found in the Full Paper by A. Bauzá et al. on page 16576. [ABSTRACT FROM AUTHOR]

The synthesis of a metalled double-helix containing exclusively silver-mediated C*−C* base pairs is reported herein (C*=N1hexylcytosine). Remarkably, it is the first crystal structure containing infinite and consecutive C*-AgI-C* base pairs that form a double helix. The AgI ion occupies the center between two C* residues with N(3)−Ag bond lengths of 2.1 Å and short AgI−AgI distances (3.1 Å) suggesting an interesting argentophilic attraction as a stabilization source of the helical disposition. The solid-state structure is further stabilized by metal-mediated base-pairs, hydrogen bonding and π-stacking interactions. Moreover, the angle N(3)−Ag-N(3) is almost linear in the [Ag(N1hexylcytosine)2]+ motif and the bases are not coplanar, thus generating a double-strand helical aggregate in the solid state. The noncovalent and argentophilic interactions have been rationalized based on DFT calculations. [ABSTRACT FROM AUTHOR]

Three solid materials, [Pb( HL)(SCN)2] ⋅CH3OH ( 1), [Pb( HL)(SCN)2] ( 2), and [Pb( L)(SCN)] n ( 3), were obtained from Pb(SCN)2 and an unsymmetrical bis-pyridyl hydrazone ligand that can act both as a bridging and as a chelating ligand. In all three the lead center is hemidirectionally coordinated and is thus sterically optimal for participation in tetrel bonding. In the crystal structures of all three compounds, the lead atoms participate in short contacts with thiocyanate sulfur or nitrogen atoms. These contacts are shorter than the sums of the van der Waals radii (3.04-3.47 Å for Pb ⋅⋅⋅S and 3.54 Å for Pb ⋅⋅⋅N) and interconnect the covalently bonded units (monomers, dimers, and 2D polymers) into supramolecular assemblies (chains and 3D structures). DFT calculations showed these contacts to be tetrel bonds of considerable energy (6.5-10.5 kcal mol−1 for Pb ⋅⋅⋅S and 16.5 kcal mol−1 for Pb ⋅⋅⋅N). A survey of structures in the CSD showed that similar contacts often appear in crystals of PbII complexes with regular geometries, which leads to the conclusion that tetrel bonding plays a significant role in the supramolecular chemistry of PbII. [ABSTRACT FROM AUTHOR]

Herein we report the use of polyether binders as regulation agents (RAs) to enhance the enantioselectivity of rhodium-catalyzed transformations. For reactions of diverse substrates mediated by rhodium complexes of the α,ω-bisphosphite-polyether ligands 1- 5, a- d, the enantiomeric excess ( ee) of hydroformylations was increased by up to 82 % (substrate: vinyl benzoate, 96 % ee), and the ee value of hydrogenations was increased by up to 5 % (substrate: N-(1-(naphthalene-1-yl)vinyl)acetamide, 78 % ee). The ligand design enabled the regulation of enantioselectivity by generation of an array of catalysts that simultaneously preserve the advantages of a privileged structure in asymmetric catalysis and offer geometrically close catalytic sites. The highest enantioselectivities in the hydroformylation of vinyl acetate with ligand 4 b were achieved by using the Rb[B(3,5-(CF3)2C6H3)4] (RbBArF) as the RA. The enantioselective hydrogenation of the substrates 10 required the rhodium catalysts derived from bisphosphites 3 a or 4 a, either alone or in combination with different RAs (sodium, cesium, or ( R, R)-bis(1-phenylethyl)ammonium salts). This design approach was supported by results from computational studies. [ABSTRACT FROM AUTHOR]

Electrophilic fluorophosphonium triflates bearing pyridyl (3[OTf]) or imidazolyl (4[OTf])‐substituents act as intramolecular frustrated Lewis pairs (FLPs) and reversibly form 1 : 1 adducts with CO2 (5+ and 6+). An unusual and labile spirocyclic tetrahedral intermediate (72+) is observed in CO2‐pressurized (0.5–2.0 bar) solutions of cation 4+ at low temperatures, as demonstrated by variable‐temperature NMR studies, which were confirmed crystallographically. In addition, cations 3+ and 4+ actively bind carbonyls, nitriles and acetylenes by 1,3‐dipolar cycloaddition, as shown by selected examples. [ABSTRACT FROM AUTHOR]

The detection of nucleotides is of crucial importance because they are the basic building blocks of nucleic acids. Scorpiand-based polyamine receptors functionalized with pyridine or anthracene units are able to form stable complexes with nucleotides in water, based on coulombic, π-π stacking, and hydrogen-bonding interactions. This behavior has been rationalized by means of an exploration with NMR spectroscopy and DFT calculations. Binding constants were determined by potentiometry. Fluorescence spectroscopy studies have revealed the potential of these receptors as sensors to effectively and selectively distinguish guanosine-5′-triphosphate (GTP) from adenosine-5′-triphosphate (ATP). [ABSTRACT FROM AUTHOR]