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In this study, a series of electron donor (–NH2, –NMe2 and –tBu) and electron-withdrawing substituents (–F, –CN and –NO2) were used to tune the nucleophilicity or electrophilicity of a series of square planar Ni2+, Pd2+ and Pt2+ malonate coordination complexes towards a pentafluoroiodobenzene and a pyridine molecule. In addition, Bader's theory of atoms in molecules (AIM), noncovalent interaction plot (NCIplot), molecular electrostatic potential (MEP) surface and natural bond orbital (NBO) analyses at the PBE0-D3/def2-TZVP level of theory were carried out to characterize and discriminate the role of the metal atom in the noncovalent complexes studied herein. We hope that the results reported herein may serve to expand the current knowledge regarding these metals in the fields of crystal engineering and supramolecular chemistry. [ABSTRACT FROM AUTHOR]

In this work, intra- and intermolecular halogen and chalcogen bonds (HlgBs and ChBs, respectively) present in the solid state of nucleic acids (NAs) have been studied at the RI-MP2/def2-TZVP level of theory. To achieve this, a Protein Data Bank (PDB) survey was carried out, revealing a series of structures in which Br/I or S/Se/Te atoms belonging to nucleobases or pentose rings were involved in noncovalent interactions (NCIs) with electron-rich species. The energetics and directionality of these NCIs were rationalized through a computational study, which included the use of Molecular Electrostatic Potential (MEP) surfaces, the Quantum Theory of Atoms in Molecules (QTAIM), and Non Covalent Interaction plot (NCIplot) and Natural Bonding Orbital (NBO) techniques. [ABSTRACT FROM AUTHOR]

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]

This manuscript shows that chalcogen bonding (ChB) interactions are enhanced by the coordination of the chalcogen atom to metal centers as evidenced using DFT calculations (PBE0-D3/def2-TZVP level of theory). X-ray structures retrieved from the Cambridge Structural Database (CSD) are used to support the enhanced ability of Se and Te-atoms coordinated to transition metals to participate in ChBs, eliminating the necessity to use strong electron-withdrawing groups bonded to the Ch atom. Orbital analysis performed using the natural bond orbital (NBO) technique discloses a large LP → σ* contribution, especially for anionic electron donors. In one example, the new σ-hole that is generated upon complexation (opposite to the Ch--M bond) plays a crucial role in the solid state, promoting the formation of infinite 1D polymers. [ABSTRACT FROM AUTHOR]

This manuscript evidences the existence and importance of spodium bonds (SpB) in solid state structures involving five-coordinated square-pyramidal Zn(II) spodium atoms. Four families of compounds have been found analysing the Cambridge structural database (CSD) where the interaction is very important to understand the crystal packing: (i) multi-dentate Schiff-base complexes, (ii) Zn-porphyrins, (iii) aza-crown ethers and (iv) polyoxometalates, the latter as SpB acceptors. The square-pyramidal around the metal center facilitates the approximation of the electron rich atom (ElR) to the Zn(II), contrariwise to the four-coordinated tetrahedral geometry where the steric crowd of the Zn ligands usually impedes the formation of the SpB. This highlight concentrates on the SpB interaction, which is different from the classical coordination bond in the sense that Y–Sp⋯A distances are longer (around the sum of van der Waals radii), the interaction weaker and it involves the σ* orbital of the Y–Sp bond (Y = any atom). A theoretical study on one representative family of compounds (Zn-porphyrins) has been also carried out indicating that the SpB energies range from −1 to −7.4 kcal mol−1. Finally, a statistical analysis of the CSD evidences that the interaction can be somewhat directional. [ABSTRACT FROM AUTHOR]

The term spodium (Sp) bond is proposed to refer to a net attractive interaction between any element of Group 12 and electron‐rich atoms (Lewis bases or anions). These noncovalent interactions are markedly different from coordination bonds (antibonding Sp–ligand orbital involved). Evidence is provided for the existence of this interaction by calculations at the RI‐MP2/aug‐cc‐pVTZ level of theory, atoms‐in‐molecules, and natural bond orbital analyses and by examining solid‐state structures in the Cambridge Structure Database. [ABSTRACT FROM AUTHOR]

The term spodium (Sp) bond is proposed to refer to a net attractive interaction between any element of Group 12 and electron‐rich atoms (Lewis bases or anions). These noncovalent interactions are markedly different from coordination bonds (antibonding Sp–ligand orbital involved). Evidence is provided for the existence of this interaction by calculations at the RI‐MP2/aug‐cc‐pVTZ level of theory, atoms‐in‐molecules, and natural bond orbital analyses and by examining solid‐state structures in the Cambridge Structure Database. [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]

Four new trinuclear hetero-metallic complexes, [(CuL) 2 (μ-X) 2 Cd] where X = Cl, Br, I and NO 3 have been synthesized using N 2 O 2 donor Schiff base ligand and structurally characterized. Non-covalent interactions (i.e. π···π, C H···O and Cu···Cu interactions) of the molecules have been characterized by means of high level DFT calculations. • Four new tri-nuclear copper(II)-cadmium(II) complexes have been synthesized. • All of the complexes have been structurally characterized. • Extensive non-covalent interactions have been observed in all of four complexes. • An exclusive C H···O interaction has been observed in crystal packing of complex 4. • These interactions have been investigated by high level DFT calculations. Four new tri-nuclear hetero-metallic copper(II)-cadmium(II) complexes [(CuL) 2 CdCl 2 ] (1), [(CuL) 2 CdBr 2 ] (2), [(CuL) 2 CdI 2 ] (3) and [(CuL) 2 Cd(NO 3) 2 ] (4) have been synthesized using [CuL] as "ligand complex" (where H 2 L = N,N′-bis(2-hydroxynaphthyl-methylidene)-1,3-propanediamine) and characterized by elemental analysis, IR, UV–Vis spectroscopy and single crystal X-ray diffraction studies. Crystal structure analyses reveal that all four complexes consist of a tri-nuclear moiety in which two square-pyramidal [CuL] units are bonded to a central Cd(II) ion through double phenoxido bridges. The Cd(II) is in a six-coordinate octahedral environment being bonded additionally to two mutually trans chloride (in 1), bromide (in 2), iodide (in 3) and oxygen atoms of nitrate (in 4) ions. Presence of several non-covalent interactions (i.e. π···π, C H···O and Cu···Cu interactions) has been observed in the crystal packing of all the four molecules that assist the formation of 1D supramolecular assemblies in the solid state. The interactions were investigated by means of high level DFT calculations (PBE0-D3/def2-TZVP) with the help of TURBOMOLE 7.0 program, characterized using Bader's theory of "atoms-in-molecules" (AIM) and rationalized using molecular electrostatic potential (MEP) surface calculations. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • σ-Hole tetrel bonding interactions: A CSD survey of tin and lead compounds. • Intra and intermolecular tetrel bonding interactions in tetravalent Sn(IV) and Pb compounds. • Tetrel bonding interactions in Pb(II) hemidirectional coordination compounds. Abstract A tetrel bond can be defined as an interaction between any electron donating moiety and a group 14 element acting as Lewis acid. Experimental and theoretical research on this interaction has rapidly grown in recent years. A reason for that is related to the fact that it can be easily exploited to design supramolecular structures. This review is devoted to highlight the role of heavier tetrel atoms (tin and lead) as promising building blocks for the construction of supramolecular assemblies and supramolecular MOFs based on tetrel bonding interactions. In the case of tin, the number of investigations on this topic is limited, therefore we also provide a survey of crystal structures retrieved from the Cambridge Structural Database where this interaction is crucial for the crystal packing stability. We have sub-divided this part taking into consideration the atom or group of atoms acting as lone pair donor atom (O, S, N, halogen) and also the intra- or intermolecular nature of the interaction. This survey evidences that close contacts between Sn and lone-pair-possessing atoms are quite common and oriented along the extension of the covalent bond formed by the Sn and the most electron-withdrawing substituent. Moreover, it provides experimental evidence of the ability to act as electrophilic site (tetrel bond donor). This ability has a prominent role upon the conformations and the packing of Tin organic derivatives in the solid state. For Pb(IV) organic compounds, where the geometry around the metal center is tetrahedral we also provide a survey of crystal structures retrieved from the Cambridge Structural Database. To our knowledge, this type of analysis in Pb(IV) is unprecedented in the literature. For Pb(II), we have selected several works where the tetrel bonding interaction is used as a robust tool in crystal engineering and supramolecular chemistry. [ABSTRACT FROM AUTHOR]

Developing chemosensors for efficient detection of Al3+ and picric acid in water is in high demand but challenging. In this paper, we have demonstrated the potential of a probe, 6,6′-(1E,1′E)-(2-hydroxypropane-1,3-diyl)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(2-methoxyphenol) (H2Vm), as a “switch-on” Al3+ responsive fluorescence chemosensor in water. In addition to the ability of H2Vm to sense Al3+, the Al2-Vm2 complex offers selectivity towards picric acid (PA) in HEPES buffer (pH = 7.4) solution (detection limit (20.13 × 10−9 M) via“switch-off” mode. The reversible fluorescence response with low detection limit (11.34 × 10−9 M) in the pH range of 6.0–9.0 makes H2Vm suitable for tracking Al3+ in live HCT cells. The resulting Al2-Vm2 complex is also responsive towards PA in HCT cells. Thus, a versatile fluorescence spectroscopy-based chemosensor for Al3+ and picric acid has been developed with possible applications in human health and national security. [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]

Five new Pb(ii) complexes of hydrazone-based and Schiff-based ligands and three different anionic co-ligands (azide, thiocyanate and bromide) have been synthesized and characterized by structural, analytical and spectroscopic methods. This variety of ligands can coordinate to the Pb(ii) metal center in a tridentate or tetradentate fashion via a different combination of any of nitrogen, oxygen and sulphur donor atoms. Moreover, the organic ligands can be in mono-deprotonated or neutral forms. By using single-crystal X-ray crystallography, we show that the synthesized complexes aggregate into larger supramolecular entities due to the formation of noncovalent tetrel bonding interactions. The Pb(ii) center is hemidirectionally coordinated even in those complexes where the coordination number is six. Consequently, this is sterically ideal for establishing tetrel bonding interactions with electron-rich nitrogen, bromide or sulphur atoms. These contacts are significantly larger than the sums of the covalent radii. Hence, they can be described as non-covalent tetrel bonding interactions. They interconnect the covalently bonded units into supramolecular assemblies (dimers or tetramers). The contribution of contacts involving the Pb atom has been studied using Hirshfeld surface analysis and fingerprint plots. We have analysed the supramolecular assemblies observed in the solid state by means of DFT calculations and characterized them using Bader's theory of atoms-in-molecules. [ABSTRACT FROM AUTHOR]

Abstract: The design, synthesis and evaluation of catalytic triads composed of a central C60 fullerene with an amine base on one side and polarizability enhancers on the other side are reported. According to an enolate addition benchmark reaction, fullerene–fullerene–amine triads display the highest selectivity in anion–π catalysis observed so far, whereas NDI–fullerene–amine triads are not much better than fullerene–amine controls (NDI=naphthalenediimide). These large differences in activity are in conflict with the small differences in intrinsic π acidity, that is, LUMO energy levels and π holes on the central fullerene. However, they are in agreement with the high polarizability of fullerene–fullerene–amine triads. Activation and deactivation of the fullerene‐centered triads by intercalators and computational data on anion binding further indicate that for functional relevance, intrinsic π acidity is less important than induced π acidity, that is, the size of the oriented macrodipole of polarizable π systems that emerges only in response to the interaction with anions and anionic transition states. The resulting transformation is thus self‐induced, the anionic intermediates and transition states create their own anion–π catalyst. [ABSTRACT FROM AUTHOR]

Combining computations and X-ray structure analysis we have demonstrated that [Pt(CN4)]2− can behave as a Lewis acid inside an enzyme's cavity. The nature of a counterintuitive contact found between a catalytically active GLN residue belonging to a mitochondrial synthase and the Pt(II) center was investigated by combining molecular dynamics and quantum mechanics calculations. Results confirm the electron acceptor role of [Pt(CN4)]2−, serving as an inspiration for the design of biomolecular cages able to tweak the nucleophilic/electrophilic character of an organometallic compound. [ABSTRACT FROM AUTHOR]

Crystal structures of aminopyridine–succinate salts (1–3) were solved by single crystal X-ray diffraction where salt bridge (SB) interactions between the succinate and protonated aminopyridine dominated their supramolecular architecture. X-ray crystallography reveals that compounds 1 (hydrogensuccinate 2-amino-5-methylpyridinium salt) and 2 (hydrogensuccinate 2-amino-4-methylpyridinium salt) exhibit C–H…SB…π+ assemblies, while compound 3 (succinato-aminopyridinium salt) displays unique N–H…SB…lone pair (l)p networks in the solid state. These unexplored extended networks are described and investigated for the first time in crystalline structures. Our study also describes the duality of the salt bridge in establishing π-facial interactions with electron rich and/or electron poor moieties depending on the positive or negative nature of the SB counterpart that interacts with the SB surface. The theoretical study combines an energetic investigation of the noncovalent forces that contribute to the extended supramolecular network and the characterization of the diverse interactions by means of Bader's theory of “atoms in molecules” (AIM) and the NCIplot index. [ABSTRACT FROM AUTHOR]

Two new bromine head-containing oxacalix[2]arene[2]triazines were designed and synthesized. Owing to the bromine head and complementary V-shaped cavity, the solid state structure of oxacalix[2]arene[2]triazine having N,N-dipropylamino substituents showed an intriguing and unique 1D-supramolecular chain-like self-assembly. To provide deep insight into the true nature of the observed stabilizing interactions, i.e., lone pair–π or σ-hole–π interactions, theoretical calculations were carried out. The computations confirm the presence of genuine σ-hole–π interactions. On the other hand, the calculations on the analogous oxacalix[2]arene[2]triazine having chlorine substituents revealed the greater π-acidic character of the s-triazine rings, thus proposing the cleft-like cavity to be more suitable for lone pair–π interactions. This is supported by retrieving the X-ray single crystal structure of the parent oxacalix[2]arene[2]triazine from the CSD which showed the existence of mixed lone pair–π/σ-hole–π and true lone pair–π interactions in the solid state. The study provides constructive clues on the utility of these macrocycles in host–guest and related fields of supramolecular chemistry. [ABSTRACT FROM AUTHOR]

Four new asymmetric Schiff bases, N - α -methylsalicylidene- N ′-2-hydroxynapthylidene-1,3-propanediamine (H 2 L 1 ), N - α -methylsalicylidene- N ΄-5-bromosalicylidene-1,3-propanediamine (H 2 L 2 ), N - α -methylsalicylidene- N ΄-3-methoxysalicylidene-1,3-propanediamine (H 2 L 3 ) and N -(3-methoxysalicylidene)- N΄ -(2-hydroxynapthylidene)-1,3-propanediamine (H 2 L 4 ) and their Cu(II) complexes [CuL 1 ] ( 1 ), [CuL 2 ] ( 2 ), [CuL 3 ] ( 3 ) and [CuL 4 ] ( 4 ) have been synthesized. All the complexes ( 1 – 4 ) have been structurally characterized by single crystal XRD. The Cu-atom is four coordinated square planar in complexes 1 – 3 but in 4 a water molecule coordinates to one of its axial positions making it penta-coordinated with square pyramidal geometry. The mononuclear complex molecules of 1 and 2 form infinite 1D columns that are arranged parallel forming 2D sheets where as in 3 they form self-assembled dimers that are inter-connected by weak van der Waals interactions and in 4 the molecules are packed in the form of infinite 1D ladders. The structure of a recently reported complex with a similar asymmetric ligand (H 2 L 5 ) N - α -methylsalicylidene- N ′-salicylidene-1,3-propanediamine where the phenoxido oxygen coordinates mutually to the axial position of another molecule to form a dimer is compared to the present complexes. The packing of the molecules in all the crystals are rationalized by theoretical molecular electrostatic potential surface (MEPS) calculations. DFT calculations show the significant role of CH·π (chelate ring) and π⋯π (chelate ring) interactions governing the crystal packing in all the complexes. Both the interactions are evaluated energetically by means of high level DFT calculations (M06-2X/def2-TZVP) and characterized using Bader's theory. Energetic differences between the monomeric and dimeric complexes in 1 and 5 have also been evaluated. [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]

Using ab initio calculations, we analyze the interplay between π‐hole interactions involving the nitro group of 1,4‐dinitrobenzene and lone pair···π (lp···π), C–H···π or metal(M)···π noncovalent interactions. Moreover, we have also used 1,4‐phenylenebis(phosphine dioxide) for comparison purposes. Interesting cooperativity effects are found when π‐hole (F···N,P) and lp···π/C–H···π/M···π interactions coexist in the same supramolecular assembly. These effects are studied theoretically in terms of energetic and geometric features of the complexes, which are computed by ab initio methods (RI‐MP2/def2‐TZVP). A charge density analysis using the Bader's theory of “atoms in molecules” is carried out to characterize the interactions and to analyze their strengthening or weakening depending on the variation of charge density at critical points. The importance of electrostatic effects on the mutual influence of the interaction is studied by means of molecular electrostatic potential calculations. By taking advantage of these computational tools, the present study examines interplay of these interactions. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A novel cyamelurate-based copper(II) coordination compound has been designed from a computational approach to show anion-π interactions between the s-heptazine core and perchlorate anions; therefore, a complex of formula {[Cu(pmta)]3cyam}(ClO4)3 (1) [pmta = N,N,N',N",N"-pentamethyl-diethylenetriamine and cyam = cyamelurate ligand] was synthesized. The cationic molecule stabilizes in the solid state with two perchlorate anions one above and the other below the cyamelurate aromatic rings in a polar conformation, crystallizing in the R3cnoncentrosymmetric space group with a close cubic packing of the cations. The binding energies were calculated to be ca. -175 kcal/mol for the two species 1:OClO3- and 1:O3ClO-, and the anion-π contribution could also be calculated, being ca. -10 kcal/mol. The dielectric and magnetic properties were analyzed showing a semiconductor behavior in the temperature range studied (300-458 K) and a weak antiferromagnetic interaction among the three Cu(II) ions. The crystals of 1 show a hollowed hexagonal prismatic morphology, with hollow diameters up to 300 μm. A mechanism based on oriented growth, dissolution, and recrystallization of the outer shell was proposed to explain these hollowed structures. [ABSTRACT FROM AUTHOR]

In this manuscript, we combined a search in the Cambridge Structural Database (CSD) and ab initio calculations (RI-MP2/def2-TZVPD level of theory) to analyze the ability of trisulphide and triselenide moieties to establish chalcogen ‘like-like’ interactions. A preliminary CSD inspection revealed two predominant structural patterns, depending on the anti or syn conformation adopted by the substituents of the S3/Se3 bridge, leading to bifurcated or double chalcogen bonding interactions, respectively. In order to analyze these two relevant structural motifs we have used a series of S and Se derivatives Ch3X2 (Ch = S and Se and X = H, F, CN, and CF3) which act as both electron donor (using the lone pairs) and acceptor (using the σ-holes) entities. Besides, we have carried out “atoms in molecules” (AIM) and natural bonding orbital (NBO) analyses to further describe and characterize the chalcogen bonding interactions described herein. As far as we know, chalcogen···chalcogen interactions involving trichalconides (S3/Se3) have not been previously described in literature a may be of great importance in the preparation and characterization of new solids based on this subclass of σ-hole bonding. [ABSTRACT FROM AUTHOR]

A supramolecular motif listed as ‘carbon bonded’ or ‘hydrogen bonded’ may have the character of both. We highlight the hybrid character of the non-covalent interaction in a bis-Schiff base of N-allyl isatin by theoretical studies, the solid state structure of which is mainly driven by a non-covalent carbon/hydrogen bonded self-complementary dimeric {…C–N–C=O/H–C–N–C=O}2 synthon. [ABSTRACT FROM AUTHOR]

In this manuscript, we combined ab initio calculations (RI-MP2/def2-TZVPD level of theory) and a search in the CSD (Cambridge Structural Database) to analyze the influence of aromatic substitution in charge-assisted multivalent halogen bonding complexes. We used a series of benzene substituted iodine derivatives C6H4(IF4)Y (Y = H, NH2, OCH3, F, CN, and CF3) as Lewis acids and used Cl- as electron rich interacting atoms. We have represented the Hammett's plot and observed a good regression coefficient (interaction energies vs. Hammett's cr parameter). Additionally, we demonstrated the direct correlation between the Hammett's cr parameter and the value of molecular electrostatic potential measured at the I atom on the extension of the C-I bond. Furthermore, we have carried out AIM (atoms in molecules) and NBO (natural bonding orbital) analyses to further describe and characterize the interactions described herein. Finally, we have carried out a search in the CSD (Cambridge Structural Database) and found several X-ray structures where these interactions are present, thus giving reliability to the results derived from the calculations. [ABSTRACT FROM AUTHOR]

Three elongated (4+1) square pyramidal copper(II) complexes, [Cu 2 (L) 2 (μ 1,1 -N 3 ) 2 ]·H 2 O ( 1 ), [Cu 2 (L) 2 (μ 1,1 -NCO) 2 ] ( 2 ) and [Cu(L)(μ 1,5 -dca)] n ( 3 ) [HL = 1((2-(methylamino)ethylimino)methyl)naphthalen-2-ol and dca = dicyanamide], have been synthesized using a tridentate N 2 O donor Schiff base ligand (HL) and characterized. Complexes 1 and 2 are centrosymmetric dimers in which copper(II) centres are connected by asymmetric double end on pseudohalide bridges. Complex 3 features a 1D zigzag chain in which copper(II) centres are connected by end to end dca bridges. Variable temperature (2–300 K) magnetic susceptibility measurements indicate the presence of antiferromagnetic exchange coupling between copper(II) centres in complexes 1 ( J = −2.313 cm −1 ) and 3 ( J = −0.344 cm −1 ), whereas complex 2 shows ferromagnetic exchange coupling between copper(II) centres ( J = 0.513 cm −1 ). DFT calculations also corroborate the data. The fluid solution EPR spectra recorded at 293 K are typical of copper(II) species. Significant supramolecular interactions are explored using high level DFT calculations (BP86-D3/def2-TZVP) and characterized by Bader’s theory of “atoms-in-molecules”. [ABSTRACT FROM AUTHOR]

In this article, ab initio calculations have been combined with a search in the Protein Data Bank (PDB) to demonstrate the importance of σ-hole tetrel bonding interactions in biological systems. In particular, we focus our attention on the ability of the -CF3 group to participate in noncovalent interactions as Lewis acids, and we show the importance of this interaction in the inhibition mechanism of a NADP+-dependent isocitrate dehydrogenase (IDH) enzyme that converts isocitrate to α-ketoglutarate. IDH mutations are found in multiple hematologic and solid tumors, inducing premalignant disorders. A potent triazine-based inhibitor of the mutant IDH (enasidenib) presents two-CF3 groups in the structure. One establishes a tetrel bonding interaction with an aspartate residue that contributes to the binding and selectivity of the inhibitor to the active site. [ABSTRACT FROM AUTHOR]

Herein we report the X-ray characterization of a pair of CCl3F (CFC-11) molecules trapped in a molecular sponge. The encapsulated molecules are arranged in two crystallographically independent relative orientations inside the channels. In one of them, uncommon C(sp3)-F . . . F-C(sp3) interactions between the CCl3F molecules are observed along with halogen (X) . . . π interactions with the walls of the channel. [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]

In this manuscript, we report the design, synthesis and X-ray characterization of nitrodiene derivatives that present crucial π–hole interactions involving the nitro group as a π–hole donor. The solid state structures of 1,4-dinitro-1,3-butadiene (1), its co-crystal 1·Diox, and homologous 1,4-dinitro-1,3-pentadiene (2) and 2,4-dinitro-2,4-hexadiene (3) feature competition of lone pair–π–hole interactions with common weak CH…O bonding and gradually increased role of the NO2…NO2 interactions. Regular evolution of the supramolecular patterns (1 to 3) results in generation of an unprecedented 3D non-covalent framework in 3 that is controlled exclusively by short π–hole contacts (O…N = 2.9615(18), 3.1304(18) Å). These findings complement the results of high level ab initio calculations (MP2/def2-TZVP) and unite theory and experiment, thus supporting the functional relevance of this novel π–hole interaction. [ABSTRACT FROM AUTHOR]

In this study, the ability of haloborane compounds to establish lone pair-π, halogen-π and triel bond interactions has been evaluated at the RI-MP2/def2-TZVPD level of theory. We have used BX (X = F, Cl, Br and I) compounds as lone pair-π, halogen-π and triel bond donors and ethene, 1,2-difluoroethene and perfluoroethene as models of π-systems. In addition, we have carried out NBO analysis indicating that orbital effects are remarkable contributors to the global stabilization of the noncovalent complexes studied. Finally, we have also used Bader's theory of 'atoms in molecules' to further analyze and characterize the noncovalent interactions described herein. [ABSTRACT FROM AUTHOR]

A novel ambiguous reactivity of Li/Cl phosphinidenoid complexes under redox conditions is described. The outcome of the reaction with hexafluoroacetone is highly dependent on the P-substituent as fluoride substitution occurred in the case of R = CPh3 and C5Me5via a radical pathway, whereas for R = CH(SiMe3)2 a complex having a novel 1,2-diol-type P-ligand was obtained via a closed-shell pathway. DFT calculations reveal a new SET pathway starting with a noncovalent π-hole complex between the phosphinidenoid anion and hexafluoroacetone followed by an elimination of LiF. The second, closed-shell reaction course is strongly influenced by a noncovalent O…Si interaction established after the initial nucleophilic attack. [ABSTRACT FROM AUTHOR]

In this study, nine mercury(ii) complexes of the composition [Hg(Ln)(X)2] (X = Cl, Br and I, n = 1–3), (L1 = 2-pyridine piconyl hydrazone); L2 = (2-acetylpyridine piconyl hydrazone) and L3 = (2-phenylpyridine piconyl hydrazone) are synthesized and spectroscopically characterized. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. Moreover, Hirshfeld surface (HS) analyses were employed to gain additional insight into interactions responsible for the packing of complexes 1–9. Quantitative examination of 2D fingerprint plots revealed, among others, the dominating participation of H…H and H…X interactions in the molecular packing. Moreover, C–H…X hydrogen bonds, π–π, and chelate-ring–π interactions are described and analysed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks. The influence of the halide on the energetic features of the assemblies has been also studied. [ABSTRACT FROM AUTHOR]

A combined energetic and geometric study of a series of triel bond complexes involving haloborane salts has been carried out at the M06-2X/def2-QZVPD level of theory. We have used 1-(dihaloboranyl)pyridin-1-ium compounds Py + BX 2 (X = Cl, Br and I) as triel bond donors and Cl − , Br − , HCO 2 − , BF 4 − and ClO 4 − as electron donor moieties. In addition we have used Bader’s theory of ‘atoms in molecules’ to further characterize the noncovalent interactions described herein. Finally, several examples were retrieved from the CSD (Cambridge Structural Database) in order to provide experimental support to the results presented in this work. [ABSTRACT FROM AUTHOR]

Two mononuclear square planar nickel(II) complexes, [Ni(HL) 2 ](ClO 4 ) 2 ( 1 ) and [Ni(HL) 2 ]Cl 2 ·2H 2 O ( 2 ), [where HL = 3-(dimethylaminopropyliminomethyl)naphthalen-2-ol] have been synthesized and characterized by elemental and spectral analysis. The structures have been confirmed by single crystal X-ray diffraction studies. In each complex, the Schiff base is present in its zwitterionic form. Interesting supra-molecular networks were generated through various non-covalent forces. Density functional theory (DFT) calculations were employed to estimate the contribution of each interaction in the formation of the assembly using several theoretical models. [ABSTRACT FROM AUTHOR]

Two new dinuclear cadmium(II) complexes, [Cd(L 1 ) 2 Cd(SeCN-κ-Se) 2 ] ( 1 ) and [Cd(L 2 ) 2 Cd(SeCN-κ-Se) 2 ] ( 2 ), where HL 1 = {2-(3-(dimethylamino)propyliminomethyl)-6-methoxyphenol} and HL 2 = {2-(3-(dimethylamino)propyliminomethyl)-6-ethoxyphenol}, have been prepared and characterized by elemental and spectral analysis and single crystal X-ray diffraction studies. Both complexes contain cadmium-selenium bonds. Non-covalent interactions were also investigated using DFT calculations at the BP86-D3/def2-TZVP level of theory. Both complexes show florescence upon irradiation with visible light. [ABSTRACT FROM AUTHOR]

A theoretical study of nitryl halide heterodimers has been carried out using SCS-RI-MP2 and CCSD(T) at the complete basis set (CBS) calculations. For this purpose, 66 heterodimers have been characterized as minima and arranged in six groups depending on the interactions involved and their geometrical arrangements. The CCSD(T)/CBS interaction energies vary between −0.6 and −11.1 kJ mol−1. The heavier the halogen atoms, the larger the interaction energies. Natural bond orbital (NBO) and “atoms-in-molecules” (AIM) theories were then used to analyze the complexes, confirming the presence of halogen, chalcogen, and π-hole interaction bonds. The largest charge-transfer energy contributions were found for halogen bonded complexes (up to 29.1 kJ mol−1). Furthermore, the physical nature of the interactions was studied using symmetry-adapted perturbation theory (SAPT) calculations, and it was concluded that dispersion was the major source of attraction, although electrostatics is important in halogen bonded complexes. [ABSTRACT FROM AUTHOR]

Herein we report the synthesis and X-ray characterization of a neutral mercury(II) complex of composition [Hg(L) 2 ] n ( 1 ), [L = N 1 -(3-hydroxypropyl)-5-fluorouracilate]. The Hg(II) is bound to the N(3) atoms of both ligands in an essentially linear geometry. Mercury also interacts through short contacts with the O(4) atoms of the uracil rings. The two bases are almost coplanar. Surprisingly, two hydroxyl groups from two different units are also weakly bound in apical positions. Single-crystal X-ray crystallography showed that the molecular complex aggregates into a coordination polymer. The packing assemblies observed in the solid state have been analysed and studied by means of theoretical DFT calculations. Unprecedented antiparallel C O⋯C–F interactions are described since they have a strong influence in the crystal packing of the complex. We have also used the Cambridge Structural Database to examine the occurrence of C O⋯C–F interaction in the solid state of X-ray structures. [ABSTRACT FROM AUTHOR]

Two new cadmium(II) complexes, [Cd(L 1 )(OOCCH 3 )(OH 2 )] ( 1 ), [Cd 2 (L 2 ) 2 (μ-1,3-SCN) 2 (CH 3 OH) 2 ] ( 2 ), have been synthesized using two halosalicylaldimine Schiff bases, HL 1 and HL 2 {where HL 1 = 2-(2-(ethylamino)ethyliminomethyl)-4-bromophenol, and HL 2 = 2-(2-(dimethylamino)ethyliminomethyl)-4-chlorophenol}, respectively. Both complexes have been characterized by elemental and spectral analysis and their structures have been confirmed by single crystal X-ray diffraction studies. Complex 1 is mononuclear and the cadmium(II) centre is apparently coordinated by a tridentate Schiff base, a water molecule and a bidentate chelating acetate. The acetate group could also be thought of as a single entity occupying just one stereochemical site as evident from the small value of chelate bite angle. Complex 2 is dinuclear and contain octahedral cadmium(II) bridged by double end-to-end thiocyanates. Supramolecular interactions in both complexes were also explored. The theoretical study, carried out using density functional theory (DFT) calculations, is devoted to the analysis of the interesting supramolecular assemblies in the solid state of the structures, paying special attention to hydrogen bonding interactions involving the coordinated solvent molecules. [ABSTRACT FROM AUTHOR]

A new series of six structurally diverse lead(ii) coordination compounds was assembled from two isomeric nicotinoylhydrazones as neutral ligands and three Pb(ii) salts with different monoanions (chloride, nitrate and thiocyanate) as starting materials. The products were isolated in good yields and were fully characterized, including by single-crystal X-ray diffraction and theoretical methods. Within the six compounds, three feature 2D metal–organic networks, two are 1D coordination polymers, and another one comprises discrete 0D dimeric units. The structures of the latter low dimensional compounds are extendable into 2D supramolecular networks. The topology of the coordination or supramolecular networks is primarily dictated by the geometry of the nicotinoylhydrazone used as a main building block. In contrast, supramolecular interactions are greatly influenced by the choice of the anion in the starting lead(ii) salt, which is demonstrated by Hirshfeld surface analysis. In fact, the topological analysis and classification of metal–organic or supramolecular underlying networks in the obtained compounds was performed, disclosed the hcb, 2C1, gek1, SP 1-periodic net (4,4)(0,2) and 3,4L83 topological types; the latter topology was documented for three compounds, including both coordination and supramolecular networks. In the two compounds containing thiocyanate moieties, there are supramolecular contacts between the thiocyanate anions and lead centres. These were shown by DFT calculations to be strong tetrel bonds (−15.3 and −16.7 kcal mol−1) between the σ-hole of the lead atom and the π-system of the thiocyanate S–C bond. [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]

Four Pb(ii) complexes of (iso)nicotinohydrazide-based ligands and different anionic coligands (azide, nitrate, acetate and iodide) have been synthesized and characterized by structural, analytical and spectroscopic methods. The mono-deprotonated or neutral forms of the ligands coordinate in a tridentate fashion via two nitrogen and one oxygen donor atoms to the Pb. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. In all four complexes the lead center is hemidirectionally coordinated and, consequently, it is sterically ideal for establishing tetrel bonding interactions. In the crystal structures of all complexes, the lead atoms participate in short contacts with nitrogen atoms. These contacts are shorter than the sums of the van der Waals radii and larger than the sums of the covalent radii. The tetrel bonding interactions interconnect the covalently bonded units (monomers or dimers) into supramolecular assemblies (chains and 3D structures). We have analysed the interesting supramolecular assemblies observed in the solid state of all four complexes by means of DFT calculations. [ABSTRACT FROM AUTHOR]

In this manuscript we report for the first time the concurrent agostic and tetrel bonding interactions involving the heaviest tetrel atom (Pb) in N′-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide–PbX complexes (X = Cl, I, NCS, NO2). [ABSTRACT FROM AUTHOR]

Tetrel (Tr) bonding is first placed into perspective as a σ-hole bonding interaction with atoms of the Tr family. An sp3 R4Tr unit has four σ-holes with which a Lewis base can form a complex. We then highlight some inspiring crystal structures where Tr bonding is obvious, followed by an account of our own work. We have shown that Tr bonding is ubiquitous in the solid state and we have highlighted that Tr bonding with carbon is possible when C is placed in the appropriate chemical context. We hope that this account serves as an initial guide and source of inspiration for others wishing to exploit this vastly underexplored interaction. [ABSTRACT FROM AUTHOR]

In this manuscript we report the synthesis and X-ray characterization of five complexes of Zn(ii) based on a N4O core carbohydrazone ligand (H2L); i.e. {[Zn4(HL)4](CH3OH)4(NO3)4} (1), {[Zn4(HL)4](ClO4)4} (2) {[Zn4(HL)4][Zn(SCN)4](NO3)2} (3) {[Zn(SCN)4](H4L)(CH3OH)2} (4) and {[Zn4(HL)4](NO3)4(H2O)} (5). Structurally characterized tetranuclear Zn(ii) complexes, as those reported herein, are scarcely found in the literature. In the crystal structures of several compounds, N–H…S hydrogen bonds, anion–π and π–hole interactions are described and analysed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks. Moreover, the noncovalent interactions have been also analysed using Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

For well over half a century part of the scientific community has been committed to understanding and predicting how molecules recognize each other. This subject of unceasing interest, ‘supramolecular chemistry’, relies on the understanding of noncovalent interactions. Among the noncovalent forces, the anion–π interaction has attracted increasing attention ever since its inception about two decades ago. This highlight article first summarizes some of the fundamental aspects of this interaction leading to several design strategies. In the main body we highlight some relevant examples that illustrate the viability of these strategies and the importance of anion–π interactions in crystal engineering. [ABSTRACT FROM AUTHOR]

Three newly synthesized zinc(II) complexes, [Zn(L)(Cl)]ClO 4 ( 1 ), [Zn(L)(Br)]ClO 4 ( 2 ) and [Zn(L)(N 3 )]ClO 4 ( 3 ), have been obtained from a tetradentate symmetrical Schiff base, N,N′-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L). All complexes have been characterized using different spectroscopic techniques including X-ray crystallography. In the three complexes, interesting anion–π/π–π/π–anion assemblies are formed in the solid state. The contribution of each interaction to the formation of the assembly has been computed using several theoretical models and density functional theory (DFT) calculations. The mutual influence of anion–π and π–π interactions has been also analyzed and a reinforcement of both interactions is demonstrated. This theoretical study is certainly important to shed light into the delicate mechanism that governs the molecular recognition and crystal packing. [ABSTRACT FROM AUTHOR]

We have recently communicated [CrystEngComm, 2015, 17, 1769–1772] the synthesis and X-ray characterization of several oxaphosphirane tungsten(0) complexes especially designed to analyse the intramolecular W–CO(lone pair)…π(arene) interaction varying the degree of fluorination in the arene. Unexpectedly, the phenyl-substituted oxaphosphirane complex showed the shortest CO…π distance in the solid state which is very close to that observed for the pentafluorophenyl derivative. Other complexes with two or three fluorine substituents exhibited longer distances. We rationalized the affinity of the M–CO moiety for both electron-rich and electron-deficient rings by considering that the interaction can be also understood as a π–π interaction where the negative part of the CO is dominant in the π-acidic arene and the positive part of the CO is dominant in the π-basic arene. This explanation was supported by DFT calculations using orbital analysis and Bader's theory of “atoms-in-molecules”. Herein, we expand the previous study with new theoretical results of some model complexes to gain insight into the energetic and geometric features of the interaction. The experimental behaviour of the 31P-NMR chemical shifts of the title compounds agrees well with previous theoretical explanation of the physical nature of the interaction. Furthermore, we analyse the crystal packing of the four X-ray structures previously communicated in order to scrutinize other interactions in the solid state that may influence the W–CO…π interaction. Finally, stronger intermolecular interactions that influence the crystal packing are also analysed using DFT calculations. [ABSTRACT FROM AUTHOR]

In this manuscript we report the synthesis and X-ray characterization of several complexes of Cu(ii), Co(ii) and Ni(ii) with 2-(N-benzimidazolyl)-pyrimidine (L) and nitrate co-ligands. Complexes 1 and 2 are trans and cis isomers, respectively, with formula [CuL2(NO3)2]. Furthermore, complexes 2, [CoL2(NO3)2] (3) and [NiL2(NO3)2] (4) are essentially isostructural with a cis-disposition of the nitrate ligands. In compounds 1–4, the coordination mode of nitrate is terminal bidentate. Finally, during the synthesis of compound 1, a few crystals of a different complex were found and separated manually from the bulk sample and characterized by X-ray diffraction. In this compound (5), the benzimidazole ring of the ligand is oxidized to benzimidazolone (L′) and the formula of this unexpected compound is [CuL′2(H2O)2](NO3)2. Complexes 1 and 5 are characterized by the presence of anion–π interactions that are relevant to the final 3D architecture and packing. In the crystal structures of the five compounds, C–H…O hydrogen bonds, anion–π and π-stacking interactions are described and analysed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks. Moreover, some unconventional interactions have been characterized using Bader's theory of atoms-in-molecules. [ABSTRACT FROM AUTHOR]

Three copper(ii) complexes, [Cu(L1)(H2O)(OClO3)]n (1), [Cu(L1)(N3)] (2) and [Cu(L2)(Cl)(H2O)] (3) [HL1 = 4-chloro-2-((quinolin-8-ylimino)methyl)phenol and HL2 = 2-ethoxy-6-((quinolin-8-ylimino)methyl)phenol], have been synthesized and characterized by elemental analyses, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. The theoretical study, carried out using density functional theory (DFT) calculations, is devoted to the analysis of the interesting supramolecular assemblies in the solid state of the structures, paying especial attention to lp –π and π–π interactions involving the quinolin-8-ylimino moiety. [ABSTRACT FROM AUTHOR]

In this manuscript, we have examined the CSD (Cambridge Structural Database) to investigate the relative ability of Te and I (in practice, the heaviest chalcogen and halogen atoms) in di- and tri-iododiorganyltellurium(IV) derivatives to establish σ-hole interactions. The geometry around the Te(IV) in this type of compound is trigonal bipyramidal where the stereoactive lone pair at Te(IV) occupies one of the equatorial positions. In the solid state, Te(IV) tends to form pseudo-octahedral coordination by establishing strong noncovalent interactions opposite to the two covalent bonds of the equatorial plane. Such contacts can also be classified as chalcogen bonds following the recommendation of the International Union of Pure and Applied Chemistry (IUPAC). Such contacts have been analyzed energetically in this work using density functional theory (DFT) calculations, rationalized using molecular electrostatic potential (MEP) surface analysis and characterized using a combination of the quantum theory of atoms in molecules (QTAIM) and noncovalent interaction plot (NCIplot) computational tools. Finally, the observation of halogen bonds and type I halogen···halogen contacts is also emphasized and compared to the chalcogen bonds. Energy decomposition analysis has also been performed to compare the physical nature of chalcogen, halogen and type I interactions. [ABSTRACT FROM AUTHOR]