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1.
The T⋅⋅⋅N tetrel bond (TB) formed between TX 3OH (T=C, Si, Ge; X=H, F) and the Lewis base N≡CM (M=H, Li, Na) is studied by ab initio calculations at the MP2/aug-cc-pVTZ level. Complexes involving TH 3OH contain a conventional TB with interaction energy less than 10 kcal/mol. This bond is substantially strengthened, approaching 35 kcal/mol and covalent character, when fluorosubstituted TF 3OH is combined with NCLi or NCNa. Along with this enhanced binding comes a near equalization of the TB T⋅⋅⋅N and the internal T−O bond lengths, and the associated structure acquires a trigonal bipyramidal shape, despite a high internal deformation energy. This structural transformation becomes more complete, and the TB is further strengthened upon adding an electron acceptor BeCl 2 to the Lewis acid and a base to the NCM unit. This same TB strengthening can be accomplished also by imposition of an external electric field. 相似文献
2.
The pairing of TFH 3 with a TH 2CH 3− anion, where T represents tetrel atoms C, Si, Ge, Sn, Pb, results in a strong direct interaction between the two T atoms. The interaction energy is sensitive to the nature of the two T atoms but can be as large as 90 kcal/mol. The noncovalent bond strength rises quickly as the basic T atom of the anion becomes smaller, or as the Lewis acid T grows larger, although there is less sensitivity to the latter atom. The electrostatic component makes up some 55–70 % of the total attraction energy. This term is well accounted for by simple combination of the maximum and minimum values of the molecular electrostatic potential of the Lewis acid and base units, respectively. The complexation induces a rearrangement in the TFH 3 molecule from tetrahedral to trigonal pyramidal. The associated deformation energy reduces the exothermicity of the complexation reaction. Electron density shift patterns reveal a density loss on the basic T atom, along with accompanying increases on the acidic T and its attached F atom. 相似文献
3.
The crystal structure of a newly synthesized compound, [PbL(Ac)] 2, (where L=2 (amino(pyrazin-2-yl) methylene) hydrazinecarbothioamide, Ac=acetate anion) exhibits a close contact between pairs of Pb atoms, suggesting a ditetrel bond, in addition to two Pb⋅⋅⋅O tetrel bonds, and two C−H⋅⋅⋅O H-bonds. The presence of this ditetrel bond as an attractive component is confirmed by various quantum chemical methods. This novelty of this particular bond is its existence even in the absence of a σ-hole on the Pb atom, which is typically considered a prerequisite for a bond of this type. From a wider perspective, a survey of the Cambridge Structural Database suggests this bond may be more common than was hitherto thought, with 44 examples of Pb⋅⋅⋅Pb contacts amongst a total number of 219 examples of T⋅⋅⋅T interactions in general (T=Si, Ge, Sn, Pb). 相似文献
4.
The potential applications of tetrel bonds involving π‐molecules in crystal materials and biological systems have prompted a theoretical investigation of the strength of π···σ‐hole tetrel bond in the systems with acetylene and its derivatives of CH 3, AuPH 3, Li, and Na as well as benzene as the π electron donors. A weak tetrel bond (Δ E < 15 kJ/mol) is found between acetylene and tetrel donor molecule TH 3F (T = C, Si, Ge, Sn, and Pb). All substituents strengthen the π tetrel bond, but the electron‐donating sodium atoms have the largest enhancing effect and the interaction energy is up to about 24 kJ/mol in C 2Na 2‐CH 3F. The electron‐donating ability of the AuPH 3 fragment is intermediate between the methyl group and alkali metal atom. The origin of the stability of the π tetrel‐bonded complex is dependent on the nature of the tetrel donor and acceptor molecules and can be regulated by the substituents. 相似文献
5.
Ab initio calculation at the MP2/aug-cc-pVTZ level has been performed on the π-hole based N …Si tetrel bonded complexes between substituted pyridines and H 2SiO. The primary aim of the study is to find out the effect of substitution on the strength and nature of this tetrel bond, and its similarity/difference with the N …C tetrel bond. Correlation between the strength of the N …Si bond and several molecular properties of the Lewis acid (H 2SiO) and base (pyridines) are explored. The properties of the tetrel bond are analyzed using AIM, NBO, and symmetry-adapted perturbation theory calculations. The complexes are characterized with short N …Si intermolecular distances and high binding energies ranging between −142.72 and −115.37 kJ/mol. The high value of deformation energy indicates significant geometrical distortion of the monomer units. The AIM and NBO analysis reveal significant coordinate covalent bond character of the N⋅⋅⋅Si π-hole bond. Sharp differences are also noticed in the orbital interactions present in the N⋅⋅⋅Si and N⋅⋅⋅C tetrel bonds. 相似文献
6.
Several σ-hole and π-hole tetrel-bonded complexes with a base H 2CX (X=O, S, Se) have been studied, in which TH 3F (T=C−Pb) and F 2TO (T=C and Si) act as the σ-hole and π-hole donors, respectively. Generally, these complexes are combined with a primary tetrel bond and a weak H-bond. Only one minimum tetrel-bonded structure is found for TH 3F, whereas two minima tetrel-bonded complexes for some F 2TO. H 2CX is favorable to engage in the π-hole complex with F 2TO relative to TH 3F in most cases, and this preference further expands for the Si complex. Particularly, the double π-hole complex between F 2SiO and H 2CX (X=S and Se) has an interaction energy exceeding 500 kJ/mol, corresponding to a covalent-bonded complex with the huge orbital interaction and polarization energy. Both the σ-hole interaction and the π-hole interaction are weaker for the heavier chalcogen atom, while the π-hole interaction involving F 2TO (T=Ge, Sn, and Pb) has an opposite change. Both types of interactions are electrostatic in nature although comparable contributions from dispersion and polarization are respectively important for the weaker and stronger interactions. 相似文献
7.
An ab initio calculation has been carried for the carbene tetrel bonded complexes CH3Y???CH2 (Y = F, CN, NC, and NO2), CH3F???CZ2 (Z = Cl and CH3), XH3F???CF2 (X = C, Si, Ge, and Sn), SiF4???CF2, and XH3F???NHC (N-heterocyclic carbene), where carbene is treated as a Lewis base and XH3Y is a Lewis acid. Formation of the tetrel bond is mainly attributed to charge transfer from the lone pair on the C atom in the carbene toward the σ* X–Y orbital and also the σ* X–H one in the strong tetrel bond. The carbene tetrel bond is strengthened/weakened by the electron-withdrawing group in the tetrel donor/acceptor and enhanced by the methyl group in C(CH3)2. NHC forms a stronger carbene tetrel bond in XH3F???NHC (X = Si, Ge, and Sn) where it exceeds that of the majority of H-bonds. Interestingly, the tetrel bond becomes stronger in the order of X = C < Ge < Sn < Si in XH3F???NHC and the largest interaction energy occurs in SiH3F???NHC, amounting to ?103 kJ/mol. The carbene tetrel bond can be strengthened by cooperative effect with the N???M interaction in trimers H2C???CH3CN???M (M = CH3CN, HCN, ICN, SbH2F, LiCN, and BeH2) and has doubled in H2C???CH3CN???BeH2. 相似文献
8.
The complexes between borazine and TH 3F/F 2TO/H 2TO (T = C, Si, Ge) are investigated with high-level quantum chemical calculations. Borazine has three sites of negative electrostatic potential: the N atom, the ring center, and the H atom of the B H bond, whereas TH 3F and F 2TO/H 2TO provide the σ-hole and π-hole, respectively, for the tetrel bond. The N atom of borazine is the favored site for both the σ and π-hole tetrel bonds. Less-stable dimers include a σ-tetrel bond to the borazine ring center and to the BH proton. The π-hole tetrel-bonded complexes are more strongly bound than are their σ-hole counterparts. Due to the coexistence of both T···N tetrel and B···O triel bonding, the complexes of borazine with F 2TO/H 2TO (T = Si and Ge) are very stable, with interaction energies up to −108 kcal/mol. The strongly bonded complexes are accompanied by substantial net charge transfer from F 2TO/H 2TO to borazine. 相似文献
9.
In order to accommodate the approach of two NCH bases, a tetrahedral TF 4 molecule (T=Si, Ge, Sn, Pb) distorts into an octahedral structure in which the two bases can be situated either cis or trans to one another. The square planar geometry of TF 4, associated with the trans arrangement of the bases, is higher in energy than its see-saw structure that corresponds to the cis trimer. On the other hand, the square geometry offers an unobstructed path of the bases to the π-holes above and below the tetrel atom and hence enjoys a higher interaction energy than is the case for the σ-holes approached by the bases in the cis arrangement. When these two effects are combined, the total binding energies are more exothermic for the cis than for the trans complexes. This preference amounts to some 3 kcal mol −1 for Sn and Pb, but is amplified for the smaller tetrel atoms. 相似文献
11.
The nature of the complexes PhTH 3 H 3ZO and PhSiF 3 H 3ZO (T = Si, Ge, and Sn; Z = N, P, and As) has been investigated at the MP2/aug’‐cc‐pVTZ(PP) level. These complexes are primarily stabilized by one T···O tetrel bond. Interaction energies of these complexes vary from 11 to 220 kJ/mol, and T···O separations from 1.89 to 3.09 Å. Charge transfer from the O lone pair into the C T and T H σ* antibonding orbitals leads to the stabilization of these complexes. The T···O tetrel bond between PhTH 3/PhSiF 3 and H 3NO exhibits a significant degree of covalence, characterized by the large interaction energy, negative energy density, and large charge transfer. Furthermore, a pentacoordinate silicon (IV) complex is formed in PhSiF 3 H 3NO with the Si···O distance almost close to the length of Si O bond. This indicates that the oxygen atom in N‐oxides shows a strong affinity to the silicon atom in organosilicon compounds. 相似文献
12.
Molecules of the type XYT = Ch (T = C, Si, Ge; Ch = S, Se; X,Y = H, CH 3, Cl, Br, I) contain a σ-hole along the T = Ch bond extension. This hole can engage with the N lone pair of NCH and NCCH 3 so as to form a chalcogen bond. In the case of T = C, these bonds are rather weak, less than 3 kcal/mol, and are slightly weakened in acetone or water. They owe their stability to attractive electrostatic energy, supplemented by dispersion, and a much smaller polarization term. Immersion in solvent reverses the electrostatic interaction to repulsive, while amplifying the polarization energy. The σ-holes are smaller for T = Si and Ge, even negative in many cases. These Lewis acids can nonetheless engage in a weak chalcogen bond. This bond owes its stability to dispersion in the gas phase, but it is polarization that dominates in solution. 相似文献
13.
A computational study of the complexes formed by TF 3OH (T=C, Si, Ge) with three nitrogen-containing bases NCH, NH 3, and imidazole (IM) is carried out at the MP2/aug-cc-pVTZ level. TF 3OH can participate in two different types of noncovalent interactions: a hydrogen bond (HB) involving the hydroxyl proton and a tetrel bond (TB) with the tetel atom T. The strength of the HB is largely unaffected by the identity of T while the TB is enhanced as T grows larger. The HB is preferred over the TB for most systems, with the exception of GeF 3OH with either NH 3 or IM. MgCl 2 engages in a Mg⋅⋅⋅O Magnesium bond (Mg-bond) with the TF 3OH O atom, which cooperatively enhances both the HB and TB. The HB strengthening is particularly large for the NH 3 or IM bases, and especially for CF 3OH, but is slowly reduced as the T atom grows larger. The TB enhancement, on the other hand, behaves in the opposite fashion, accelerating for the larger T atoms. As a bottom line, the Mg-bond generally reinforces and accentuates the preference for the HB or TB that is already present in the dimer. The Mg-bond is also responsible for a proton transfer in the HB configurations with NH 3 and IM. 相似文献
14.
Tetrel bond, a weak noncovalent interaction between the σ-hole of a Group IV element (silicon in our case) and the cloud of an electronegative element (oxygen in our case) is the focus of this work. The percentage strengthening of tetrel bond has been investigated by optimizing 16 binary complexes of halogenated silane and water of general formula SiX nH 4−n−H 2O and 16 ternary complexes, of general formula NaX−SiX nH 4−n−H 2O, where X=F, Cl, Br and I and n=1, 2, 3 and 4 at various levels of theory defined within the formalism of density functional theory (DFT). With the addition of NaX, tetrel bond between Si and O in SiX nH 4−n−H 2O gets strengthened up to 49 %, owing to cooperativity effect exerted by hydrogen bonding between X and H in the ternary complex NaX−SiX nH 4−n−H 2O. In the series of complexes studied here, overall stabilization due to cooperativity lies between 10 kJ/mol to 170 kJ/mol. This large extent of reinforcement due to cooperativity has never been showcased before. The exceptional stabilization and reinforcement owe its genesis to the transformation of the ternary complex into a cluster orchestrated by the H-bonding in most of the cases and covalent bonding in few of the cases. 相似文献
15.
Quantum chemical calculations are applied to study the complexes between X 2TO (X = H, F, Cl, Br, CH 3; T = C, Si, Ge, Sn) and CO 2. The carbon atom of CO 2 as a Lewis acid participates in the C···O carbon bond, whereas its oxygen atom as a base engages in the O···T tetrel bond with X 2TO. Most of complexes are stabilized by a combination of both C···O and O···T interactions. The interaction energy increases in the T = C < Ge < Sn < Si sequence for most complexes. Both the electron-withdrawing halogen group and the electron-donating methyl group increase the interaction energy, up to 51 kJ/mol in F 2SiO···CO 2. One F 2SiO molecule can bind with different numbers of CO 2 molecules (1–4); as the number of CO 2 molecules increases, the average interaction energy for each CO 2 decreases and each CO 2 molecule can contribute with at least 27 kJ/mol. Therefore, silicon-containing molecules are good absorbents for CO 2. 相似文献
16.
1,1,2,2-Tetracyanocyclopropane derivatives 1 and 2 were designed and synthesized to probe the utility of sp 3-C centred tetrel bonding interactions in crystal engineering. The crystal packing of 1 and 2 and their 1,4-dioxane cocrystals is dominated by sp 3-C(CN) 2⋅⋅⋅O interactions, has significant C⋅⋅⋅O van der Waals overlap (≤0.266 Å) and DFT calculations indicate interaction energies of up to −11.0 kcal mol −1. A cocrystal of 2 with 1,4-thioxane reveals that the cyclopropane synthon prefers interacting with O over S. Computational analyses revealed that the electropositive C 2(CN) 4 pocket in 1 and 2 can be seen as a strongly directional ‘tetrel-bond donor’, similar to halogen bond or hydrogen bond donors. This disclosure is expected to have implications for the utility of such ‘tetrel bond donors’ in molecular disciplines such as crystal engineering, supramolecular chemistry, molecular recognition and medicinal chemistry. 相似文献
17.
MCO 3 (M=Zn, Cd, Hg) forms a spodium bond with nitrogen-containing bases (HCN, NHCH 2, NH 3) and a pnicogen bond with FH 2Z (Z=P, As, Sb). The spodium bond is very strong with the interaction energy ranging from −31 kcal/mol to −56 kcal/mol. Both NHCH 2 and NH 3 have an equal electrostatic potential on the N atom, but the corresponding interaction energy is differentiated by 1.5–4 kcal/mol due to the existence of spodium and hydrogen bonds in the complex with NHCH 2 as the electron donor. The spodium bond is weakest in the HCN complex, which is not consistent with the change of the binding distance. The spodium bond becomes stronger in the CdCO 3<ZnCO 3<HgCO 3 sequence although the positive electrostatic potential on the Hg atom is smallest. This is because the electrostatic interaction is dominant in the spodium-bonded complexes of CdCO 3 and ZnCO 3 but the polarization interaction in that of HgCO 3. The pnicogen bond is much weaker than the spodium bond and the former has a larger enhancement than the latter in the FH 2Z⋅⋅⋅OCO 2M⋅⋅⋅N-base ternary complexes. 相似文献
18.
A tetrel bond – an interaction between a Group 14 element acting as Lewis acid centre and an electron‐donating moiety – is analysed for ZF 4 (Z = Sn, Pb) complexes with NH 3 and HCN species. MP2/aug‐cc‐pVTZ calculations were performed and supported by results of the quantum theory of atoms in molecules. The results of calculations show that the tetrel centre may be considered as a pentavalent one if ZF 4 interacts with one NH 3 or HCN ligand or even as a hexavalent centre if it interacts with two ligands; thus the hypervalency phenomenon is discussed for the complexes analysed here. The theoretical analysis is supported by a discussion of the crystal structures containing the SnF 4 fragment; these structures are characterized by a hexa‐coordinated tin centre. 相似文献
19.
Three solid materials, [Pb( HL )(SCN) 2] ? CH 3OH ( 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 Pb II complexes with regular geometries, which leads to the conclusion that tetrel bonding plays a significant role in the supramolecular chemistry of Pb II. 相似文献
20.
The ability of the central M atom of the MCl 3− anion, with M=Be, Mg, Ca, Sr, Ba, to engage in a noncovalent bond with an approaching nucleophile is gauged by ab initio methods. The N atom of pyridine forms a M⋅⋅⋅N bond with an interaction energy between 12 and 21 kcal mol −1, even though the π-hole above the M atom is not necessarily positive in sign. Despite a strong Coulombic repulsion between two anions, CN − is also able to approach the M atom so as to engage in a metastable complex that is higher in energy than the individual anions. The energy barrier separating this complex from its constituent anion pair is roughly 20 kcal mol −1. Despite the endothermic formation reaction energy of the CN −⋅⋅⋅MCl 3− complex, the electron topology signals a strong interaction, more so than in pyridine⋅⋅⋅MCl 3− with its exothermic binding energy. The dianionic complex is held together largely on the strength of interorbital interactions, thereby overcoming a repulsive electrostatic component. The latter is partially alleviated by the pyramidalization of the MCl 3 unit which makes its π-hole more positive. The complex sinks below the separate monomers in energy when the system is immersed in an aqueous medium, with a binding energy that varies from as much as 20 kcal mol −1 for Be down to 1.2 kcal mol −1 for Ba. 相似文献
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