scholarly journals The Nature of Triel Bonds, a Case of B and Al Centres Bonded with Electron Rich Sites

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2703 ◽  
Author(s):  
Sławomir J. Grabowski
Keyword(s):  
Lewis Acids ◽  
Weak Interactions ◽  
Lewis Base ◽  
Basis Set ◽  
Strong Interactions ◽  
Orbital Method ◽  
Covalent Bonds ◽  
Moller Plesset ◽  
Intermolecular Distances ◽  
Base Units

The second-order Møller–Plesset perturbation theory calculations with the aug-cc-pVTZ basis set were performed on complexes of triel species: BCl3, BH3, AlCl3, and AlH3 acting as Lewis acids through the B or Al centre with Lewis base units: NCH, N2, NH3, and Cl− anion. These complexes are linked by triel bonds: B/Al⋅⋅⋅N or B/Al⋅⋅⋅Cl. The Quantum Theory of ´Atoms in Molecules´ approach, Natural Bond Orbital method, and the decomposition of energy of interaction were applied to characterise the latter links. The majority of complexes are connected through strong interactions possessing features of covalent bonds and characterised by short intermolecular distances, often below 2 Å. The BCl3⋅⋅⋅N2 complex is linked by a weak interaction corresponding to the B⋅⋅⋅N distance of ~3 Å. For the BCl3⋅⋅⋅NCH complex, two configurations corresponding to local energetic minima are observed, one characterised by a short B⋅⋅⋅N distance and a strong interaction and another one characterised by a longer B⋅⋅⋅N distance and a weak triel bond. The tetrahedral triel structure is observed for complexes linked by strong triel bonds, while, for complexes connected by weak interactions, the structure is close to the trigonal pyramid, particularly observed for the BCl3⋅⋅⋅N2 complex.

scholarly journals Molecular Hydrogen as a Lewis Base in Hydrogen Bonds and Other Interactions

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3294 ◽  
Author(s):  
Sławomir J. Grabowski
Keyword(s):  
Hydrogen Bonds ◽  
Molecular Hydrogen ◽  
Spectroscopic Properties ◽  
Lewis Base ◽  
Basis Set ◽  
Orbital Method ◽  
Topological Parameters ◽  
Theoretical Approaches ◽  
Strength Of Interaction ◽  
Moller Plesset

The second-order Møller–Plesset perturbation theory calculations with the aug-cc-pVTZ basis set were performed for complexes of molecular hydrogen. These complexes are connected by various types of interactions, the hydrogen bonds and halogen bonds are most often represented in the sample of species analysed; most interactions can be classified as σ-hole and π-hole bonds. Different theoretical approaches were applied to describe these interactions: Quantum Theory of ‘Atoms in Molecules’, Natural Bond Orbital method, or the decomposition of the energy of interaction. The energetic, geometrical, and topological parameters are analysed and spectroscopic properties are discussed. The stretching frequency of the H-H bond of molecular hydrogen involved in intermolecular interactions is considered as a parameter expressing the strength of interaction.

scholarly journals Non-Covalent Interactions Involving Alkaline-Earth Atoms and Lewis Bases B: An ab Initio Investigation of Beryllium and Magnesium Bonds, B···MR2 (M = Be or Mg, and R = H, F or CH3)

Inorganics ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 35 ◽  
Author(s):  
Ibon Alkorta ◽  
Anthony Legon
Keyword(s):  
Ab Initio ◽  
Lewis Acids ◽  
Alkaline Earth ◽  
Basis Set ◽  
Covalent Bonds ◽  
Lewis Bases ◽  
Complete Basis Set ◽  
Definition Of ◽  
The Individual ◽  
Equilibrium Dissociation

Geometries, equilibrium dissociation energies (De), intermolecular stretching, and quadratic force constants (kσ) determined by ab initio calculations conducted at the CCSD(T)/aug-cc-pVTZ level of theory, with De obtained by using the complete basis set (CBS) extrapolation [CCSD(T)/CBS energy], are presented for the B···BeR2 and B···MgR2 complexes, where B is one of the following Lewis bases: CO, H2S, PH3, HCN, H2O or NH3, and R is H, F or CH3. The BeR2 and MgR2 precursor molecules were shown to be linear and non-dipolar. The non-covalent intermolecular bond in the B···BeR2 complexes is shown to result from the interaction of the electrophilic band around the Be atom of BeR2 (as indicated by the molecular electrostatic potential surface) with non-bonding electron pairs of the base, B, and may be described as a beryllium bond by analogy with complexes such as B···CO2, which contain a tetrel bond. The conclusions for the B···MgR2 series are similar and a magnesium bond can be correspondingly invoked. The geometries established for B···BeR2 and B···MgR2 can be rationalized by a simple rule previously enunciated for tetrel-bonded complexes of the type B···CO2. It is also shown that the dissociation energy, De, is directly proportional to the force constant, kσ, in each B···MR2 series, but with a constant of proportionality different from that established for many hydrogen-bonded B···HX complexes and halogen-bonded B···XY complexes. The values of the electrophilicity, EA, determined from the De for B···BeR2 complexes for the individual Lewis acids, A, reveal the order A = BeF2 > BeH2 > Be(CH3)2—a result that is consistent with the −I and +I effects of F and CH3 relative to H. The conclusions for the MgR2 series are similar but, for a given R, they have smaller electrophilicities than those of the BeR2 series. A definition of alkaline-earth non-covalent bonds is presented.

Investigation by NMR spectroscopy of the structural characteristics of modified oligo-nucleotides with pendant porphyrins

2019 ◽  
Vol 23 (07n08) ◽  
pp. 797-812 ◽  
Author(s):  
Sonja Merkaš ◽  
Mladen Žinić ◽  
Régis Rein ◽  
Nathalie Solladié
Keyword(s):  
Nmr Spectroscopy ◽  
Structural Characteristics ◽  
Strong Interactions ◽  
Light Harvesting Complexes ◽  
The Past ◽  
Naturally Occurring ◽  
Nmr Data ◽  
Intermolecular Distances ◽  
Uracil Base ◽  
Biopolymer Scaffolds

During the past years, we focused on exerting control over the position and distance of porphyrins along our specifically designed oligonucleotidic scaffold. Indeed, in naturally occurring light-harvesting complexes, biopolymer scaffolds hold pigments at intermolecular distances that optimize photon capture, electronic coupling, and energy transfer. To this end, four uridine-porphyrin conjugates (a monomer, a dimer, a tetramer and an octamer) were subjected to a comprehensive conformational analysis by using NMR spectroscopy. The collected NOE NMR data highlighted characteristic and strong interactions indicating that the glycosidic angle between the ribose and uracil base is anti. In order to further investigate the conformation of this family of molecules, NMR experiments were carried out at variable temperatures. At low temperature, the signals of the porphyrinic protons decoalesce, showing two sets of [Formula: see text]-pyrrolic protons. Similar observations are made for signals corresponding to sugar moieties and especially the H1′ protons, indicating molecular motions within our porphyrin-uridin arrays. These results testify in favor of the existence of a dynamic process between C3′-endo and C2′-endo conformations.

Lewis Base Activation of Lewis Acids:  Development of a Lewis Base Catalyzed Selenolactonization

2007 ◽  
Vol 9 (19) ◽  
pp. 3801-3804 ◽  
Author(s):  
Scott E. Denmark ◽  
William R. Collins
Keyword(s):  
Lewis Acids ◽  
Lewis Base

Lewis Base Activation of Lewis Acids. Addition of Silyl Ketene Acetals to Aldehydes

2002 ◽  
Vol 124 (45) ◽  
pp. 13405-13407 ◽  
Author(s):  
Scott E. Denmark ◽  
Thomas Wynn ◽  
Gregory L. Beutner
Keyword(s):  
Lewis Acids ◽  
Lewis Base ◽  
Ketene Acetals ◽  
Silyl Ketene Acetals

scholarly journals Ab initio study of mechanism of forming a Si-heterocyclic spiro-Sn-heterocyclic ring compound by cycloaddition reaction of Me2Si=Sn: and ethene

2019 ◽  
Vol 44 (2) ◽  
pp. 114-121
Author(s):  
Xiaojun Tan ◽  
Xiuhui Lu
Keyword(s):  
Singlet State ◽  
Cycloaddition Reaction ◽  
Chemical Species ◽  
Heterocyclic Ring ◽  
Basis Set ◽  
Cycloaddition Reactions ◽  
Unoccupied Orbital ◽  
Donor Acceptor ◽  
Moller Plesset ◽  
First Time

X2Si=Sn: (X = H, Me, F, Cl, Br, Ph, Ar, etc.) are a new chemical species. The cycloaddition reactions of X2Si=Sn: are a new field of stannylene chemistry. The mechanism of the cycloaddition reaction between singlet state Me2Si=Sn: and ethene has been investigated for the first time here using second-order Møller-Plesset perturbation theory together with the 6-311++G** basis set for C, H and Si atoms and the LanL2dz basis set for Sn atoms. From the potential energy profile, it could be predicted that the reaction has one dominant reaction channel. The reaction process presented is that the 5p unoccupied orbital of Sn in Me2Si=Sn: and the π orbital of ethene form a π → p donor–acceptor bond resulting in the formation of an intermediate. The instability of this intermediate makes it isomerize to a four-membered Si-heterocyclic ring stannylene. Because the 5p unoccupied orbital of the Sn atom in the four-membered Si-heterocyclic ring stannylene and the π orbital of ethene form a π → p donor–acceptor bond, the four-membered Si-heterocyclic ring stannylene further combines with ethene to form another intermediate. Because the Sn atom in this intermediate assumes sp3 hybridization after the transition state, the intermediate isomerizes to a Si-heterocyclic spiro-Sn-heterocyclic ring compound. This result indicates the modes of cycloaddition reactions between X2Si=Sn: and symmetric π-bonded compounds, i.e. this study opens up a new field for stannylene chemistry.

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