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Anthony C. Legon - One of the best experts on this subject based on the ideXlab platform.
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a chalcogen Bonded complex h3n s c s formed by ammonia and carbon disulfide characterised by chirped pulse broadband microwave spectroscopy
Journal of Chemical Physics, 2019Co-Authors: Eva Gougoula, Nicholas R Walker, Ibon Alkorta, Chris Medcraft, Anthony C. LegonAbstract:Ground-state rotational spectra were observed for ten symmetric-top isotopologues H3N⋯S=C=S, H3N⋯34S=C=S, H3N⋯S=C=34S, H3N⋯S=13C=S, H315N⋯S=C=S, H315N⋯34S=C=S, H315N⋯S=C=34S, H315N⋯S=13C=S, H315N⋯33S=C=S, and H315N⋯S=C=33S, the first five in their natural abundance in a mixture of ammonia and carbon disulphide in argon and the second group with enriched 15NH3. The four asymmetric-rotor isotopomers H2DN⋯S=C=S, H2DN⋯34S=C=S, H2DN⋯S=C=34S, and HD2N⋯S=C=S were investigated by using a sample composed of ND3 mixed with CS2. Rotational constants, centrifugal distortion constants, and 33S nuclear quadrupole coupling constants were determined from spectral analyses and were interpreted with the aid of models of the complex to determine its symmetry, geometry, one measure of the strength of the Intermolecular binding, and information about the subunit dynamics. The complex has C3v symmetry, with nuclei in the order H3N⋯S=C=S, thereby establishing that the non-covalent interaction is a chalcogen Bond involving the non-Bonding electron pair of ammonia as the nucleophile and the axial region near one of the S atoms as the electrophile. The small Intermolecular stretching force constant kσ = 3.95(5) N m−1 indicates a weak interaction and suggests the assumption of unperturbed component geometries on complex formation. A simple model used to account for the contribution of the subunit angular oscillations to the zero-point motion leads to the Intermolecular Bond length r(N⋯S) = 3.338(10) A.Ground-state rotational spectra were observed for ten symmetric-top isotopologues H3N⋯S=C=S, H3N⋯34S=C=S, H3N⋯S=C=34S, H3N⋯S=13C=S, H315N⋯S=C=S, H315N⋯34S=C=S, H315N⋯S=C=34S, H315N⋯S=13C=S, H315N⋯33S=C=S, and H315N⋯S=C=33S, the first five in their natural abundance in a mixture of ammonia and carbon disulphide in argon and the second group with enriched 15NH3. The four asymmetric-rotor isotopomers H2DN⋯S=C=S, H2DN⋯34S=C=S, H2DN⋯S=C=34S, and HD2N⋯S=C=S were investigated by using a sample composed of ND3 mixed with CS2. Rotational constants, centrifugal distortion constants, and 33S nuclear quadrupole coupling constants were determined from spectral analyses and were interpreted with the aid of models of the complex to determine its symmetry, geometry, one measure of the strength of the Intermolecular binding, and information about the subunit dynamics. The complex has C3v symmetry, with nuclei in the order H3N⋯S=C=S, thereby establishing that the non-covalent interaction is a chalcogen Bond involving the n...
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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)
MDPI AG, 2019Co-Authors: Ibon Alkorta, Anthony C. LegonAbstract: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
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an ab initio investigation of the geometries and binding strengths of tetrel pnictogen and chalcogen Bonded complexes of co2 n2o and cs2 with simple lewis bases some generalizations
Molecules, 2018Co-Authors: Ibon Alkorta, Anthony C. LegonAbstract:Geometries, equilibrium dissociation energies (De), and Intermolecular stretching, quadratic force constants (kσ) are presented for the complexes B⋯CO2, B⋯N2O, and B⋯CS2, where B is one of the following Lewis bases: CO, HCCH, H2S, HCN, H2O, PH3, and NH3. The geometries and force constants were calculated at the CCSD(T)/aug-cc-pVTZ level of theory, while generation of De employed the CCSD(T)/CBS complete basis-set extrapolation. The non-covalent, Intermolecular Bond in the B⋯CO2 complexes involves the interaction of the electrophilic region around the C atom of CO2 (as revealed by the molecular electrostatic surface potential (MESP) of CO2) with non-Bonding or π-Bonding electron pairs of B. The conclusions for the B⋯N2O series are similar, but with small geometrical distortions that can be rationalized in terms of secondary interactions. The B⋯CS2 series exhibits a different type of geometry that can be interpreted in terms of the interaction of the electrophilic region near one of the S atoms and centered on the C∞ axis of CS2 (as revealed by the MESP) with the n-pairs or π-pairs of B. The tetrel, pnictogen, and chalcogen Bonds so established in B⋯CO2, B⋯N2O, and B⋯CS2, respectively, are rationalized in terms of some simple, electrostatically based rules previously enunciated for hydrogen- and halogen-Bonded complexes, B⋯HX and B⋯XY. It is also shown that the dissociation energy De is directly proportional to the force constant kσ, with a constant of proportionality identical within experimental error to that found previously for many B⋯HX and B⋯XY complexes.
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a two force constant model for complexes b m x b is a lewis base and mx is any diatomic molecule Intermolecular stretching force constants from centrifugal distortion constants dj or δj
Journal of Chemical Physics, 2016Co-Authors: Dror M Bittner, Nicholas R Walker, Anthony C. LegonAbstract:A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any diatomic molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M–X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJe or ΔJe, the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of Intermolecular Bond. For example, the Intermolecular Bond of B⋯MX can be a hydrogen Bond if MX is a hydrogen halide, a halogen-Bond if MX is a dihalogen molecule, or a stronger, coinage-metal Bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibri...
Ibon Alkorta - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen vs. Halogen Bonds in 1-Halo-Closo-Carboranes.
Materials, 2020Co-Authors: Ibon Alkorta, José Elguero, Josep M. Oliva-enrichAbstract:A theoretical study of the hydrogen Bond (HB) and halogen Bond (XB) complexes between 1-halo-closo-carboranes and hydrogen cyanide (NCH) as HB and XB probe has been carried out at the MP2 computational level. The energy results show that the HB complexes are more stable than the XBs for the same system, with the exception of the isoenergetic iodine derivatives. The analysis of the electron density with the quantum theory of atoms in molecules (QTAIM) shows the presence of a unique Intermolecular Bond critical point with the typical features of weak noncovalent interactions (small values of the electron density and positive Laplacian and total energy density). The natural energy decomposition analysis (NEDA) of the complexes shows that the HB and XB complexes are dominated by the charge-transfer and polarization terms, respectively. The work has been complemented with a search in the CSD database of analogous complexes and the comparison of the results, with those of the 1-halobenzene:NCH complexes showing smaller binding energies and larger Intermolecular distances as compared to the 1-halo-closo-carboranes:NCH complexes.
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a chalcogen Bonded complex h3n s c s formed by ammonia and carbon disulfide characterised by chirped pulse broadband microwave spectroscopy
Journal of Chemical Physics, 2019Co-Authors: Eva Gougoula, Nicholas R Walker, Ibon Alkorta, Chris Medcraft, Anthony C. LegonAbstract:Ground-state rotational spectra were observed for ten symmetric-top isotopologues H3N⋯S=C=S, H3N⋯34S=C=S, H3N⋯S=C=34S, H3N⋯S=13C=S, H315N⋯S=C=S, H315N⋯34S=C=S, H315N⋯S=C=34S, H315N⋯S=13C=S, H315N⋯33S=C=S, and H315N⋯S=C=33S, the first five in their natural abundance in a mixture of ammonia and carbon disulphide in argon and the second group with enriched 15NH3. The four asymmetric-rotor isotopomers H2DN⋯S=C=S, H2DN⋯34S=C=S, H2DN⋯S=C=34S, and HD2N⋯S=C=S were investigated by using a sample composed of ND3 mixed with CS2. Rotational constants, centrifugal distortion constants, and 33S nuclear quadrupole coupling constants were determined from spectral analyses and were interpreted with the aid of models of the complex to determine its symmetry, geometry, one measure of the strength of the Intermolecular binding, and information about the subunit dynamics. The complex has C3v symmetry, with nuclei in the order H3N⋯S=C=S, thereby establishing that the non-covalent interaction is a chalcogen Bond involving the non-Bonding electron pair of ammonia as the nucleophile and the axial region near one of the S atoms as the electrophile. The small Intermolecular stretching force constant kσ = 3.95(5) N m−1 indicates a weak interaction and suggests the assumption of unperturbed component geometries on complex formation. A simple model used to account for the contribution of the subunit angular oscillations to the zero-point motion leads to the Intermolecular Bond length r(N⋯S) = 3.338(10) A.Ground-state rotational spectra were observed for ten symmetric-top isotopologues H3N⋯S=C=S, H3N⋯34S=C=S, H3N⋯S=C=34S, H3N⋯S=13C=S, H315N⋯S=C=S, H315N⋯34S=C=S, H315N⋯S=C=34S, H315N⋯S=13C=S, H315N⋯33S=C=S, and H315N⋯S=C=33S, the first five in their natural abundance in a mixture of ammonia and carbon disulphide in argon and the second group with enriched 15NH3. The four asymmetric-rotor isotopomers H2DN⋯S=C=S, H2DN⋯34S=C=S, H2DN⋯S=C=34S, and HD2N⋯S=C=S were investigated by using a sample composed of ND3 mixed with CS2. Rotational constants, centrifugal distortion constants, and 33S nuclear quadrupole coupling constants were determined from spectral analyses and were interpreted with the aid of models of the complex to determine its symmetry, geometry, one measure of the strength of the Intermolecular binding, and information about the subunit dynamics. The complex has C3v symmetry, with nuclei in the order H3N⋯S=C=S, thereby establishing that the non-covalent interaction is a chalcogen Bond involving the n...
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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)
MDPI AG, 2019Co-Authors: Ibon Alkorta, Anthony C. LegonAbstract: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
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an ab initio investigation of the geometries and binding strengths of tetrel pnictogen and chalcogen Bonded complexes of co2 n2o and cs2 with simple lewis bases some generalizations
Molecules, 2018Co-Authors: Ibon Alkorta, Anthony C. LegonAbstract:Geometries, equilibrium dissociation energies (De), and Intermolecular stretching, quadratic force constants (kσ) are presented for the complexes B⋯CO2, B⋯N2O, and B⋯CS2, where B is one of the following Lewis bases: CO, HCCH, H2S, HCN, H2O, PH3, and NH3. The geometries and force constants were calculated at the CCSD(T)/aug-cc-pVTZ level of theory, while generation of De employed the CCSD(T)/CBS complete basis-set extrapolation. The non-covalent, Intermolecular Bond in the B⋯CO2 complexes involves the interaction of the electrophilic region around the C atom of CO2 (as revealed by the molecular electrostatic surface potential (MESP) of CO2) with non-Bonding or π-Bonding electron pairs of B. The conclusions for the B⋯N2O series are similar, but with small geometrical distortions that can be rationalized in terms of secondary interactions. The B⋯CS2 series exhibits a different type of geometry that can be interpreted in terms of the interaction of the electrophilic region near one of the S atoms and centered on the C∞ axis of CS2 (as revealed by the MESP) with the n-pairs or π-pairs of B. The tetrel, pnictogen, and chalcogen Bonds so established in B⋯CO2, B⋯N2O, and B⋯CS2, respectively, are rationalized in terms of some simple, electrostatically based rules previously enunciated for hydrogen- and halogen-Bonded complexes, B⋯HX and B⋯XY. It is also shown that the dissociation energy De is directly proportional to the force constant kσ, with a constant of proportionality identical within experimental error to that found previously for many B⋯HX and B⋯XY complexes.
Charles D Eggleton - One of the best experts on this subject based on the ideXlab platform.
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effect of cell and microvillus mechanics on the transmission of applied loads to single Bonds in dynamic force spectroscopy
Biophysical Journal, 2012Co-Authors: V K Gupta, Charles D EggletonAbstract:Receptor-ligand interactions that mediate cellular adhesion are often subjected to forces that regulate their detachment via modulating off-rates. Although the dynamics of detachment is primarily controlled by the physical chemistry of adhesion molecules, cellular features such as cell deformability and microvillus viscoelasticity have been shown to affect the rolling velocity of leukocytes in vitro through experiments and simulation. In this work, we demonstrate via various micromechanical models of two cells adhered by a single (intramolecular) Bond that cellular viscoelasticity resulting from the interplay of cellular deformation and hydrodynamic drag modulates transmission of an applied external load to an intramolecular Bond, and thus the dynamics of detachment. Specifically, it is demonstrated that the Intermolecular Bond force is not equivalent to the instantaneous applied force and that the instantaneous Bond force decreases with increasing cellular viscoelasticity. As cellular compliance increases, not only does the time lag between the applied load and the Bond force increase, an initial response time is observed during which cell deformation is observed without transfer of force to the Bond. It is further demonstrated that following tether formation the instantaneous intramolecular Bond force increases linearly at a rate dependent on microvillus viscosity. Monte Carlo simulations with fixed kinetic parameters predict that both cell and microvillus compliance increase the average rupture time, although the average rupture force based on Bond length remains nearly unchanged.
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effect of cell and microvillus mechanics on the transmission of applied loads to single Bonds in dynamic force spectroscopy
Physical Review E, 2011Co-Authors: V K Gupta, Charles D EggletonAbstract:Receptor-ligand interactions that mediate cellular adhesion are often subjected to forces that regulate their detachment via modulating off-rates. Although the dynamics of detachment is primarily controlled by the physical chemistry of adhesion molecules, cellular features such as cell deformability and microvillus viscoelasticity have been shown to affect the rolling velocity of leukocytes in vitro through experiments and simulation. In this work, we demonstrate via various micromechanical models of two cells adhered by a single (intramolecular) Bond that cell deformability and microvillus viscoelasticity modulate transmission of an applied external load to an intramolecular Bond, and thus the dynamics of detachment. Specifically, it is demonstrated that the Intermolecular Bond force is not equivalent to the instantaneous applied force and that the instantaneous Bond force decreases with cellular and microvillus compliance. As cellular compliance increases, not only does the time lag between the applied load and the Bond force increase, an initial response time is observed during which cell deformation is observed without transfer of force to the Bond. It is further demonstrated that following tether formation the instantaneous intramoleular Bond force increases linearly at a rate dependent on microvillus viscosity. Monte Carlo simulations with fixed kinetic parameters predict that both cell and microvillus compliance increase the average rupture time, although the average rupture force based on Bond length remains nearly unchanged.
Fernando Pirani - One of the best experts on this subject based on the ideXlab platform.
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investigation of strength and nature of the weak Intermolecular Bond in nh2 radical noble gas atom adducts and evaluation of their basic spectroscopic features
Chemical Physics Letters, 2021Co-Authors: Rafael Ferreira De Menezes, Luiz Guilherme Machado De Macedo, Joao B L Martins, Fernando Pirani, Ricardo GarganoAbstract:Abstract The NH2-Ng Intermolecular interactions are characterized exploiting a combined theoretical-phenomenological approach that suggests the use of effective interaction potential energy curves for the evaluation of fundamental spectroscopic properties of the formed weakly bound adducts. Lifetime studies reveal that, with the exception of NH2-He, all other compounds are considered stable in the 200–500 K temperature range. CCSD(T)/aug-cc-pVTZ calculations and NBO analysis suggest that induction-polarization interaction contribution plays a limited role and that charge transfer is small and appreciable only in complexes formed by the heavier Ng. SAPT0 and NCI analyses confirm that NH2-Ng systems are held together by van der Waals forces.
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the Intermolecular interaction in d2 cx4 and o2 cx4 x f cl systems molecular beam scattering experiments as a sensitive probe of the selectivity of charge transfer component
Journal of Chemical Physics, 2016Co-Authors: David Cappelletti, Stefano Falcinelli, Fernando PiraniAbstract:Gas phase collisions of a D2 projectile by CF4 and by CCl4 targets have been investigated with the molecular beam technique. The integral cross section, Q, has been measured for both collisional systems in the thermal energy range and oscillations due to the quantum "glory" interference have been resolved in the velocity dependence of Q. The analysis of the measured Q(v) data provided novel information on the anisotropic potential energy surfaces of the studied systems at intermediate and large separation distances. The relative role of the most relevant types of contributions to the global interaction has been characterized. Extending the phenomenology of a weak Intermolecular halogen Bond, the present work demonstrates that while D2 - CF4 is basically bound through the balance between size (Pauli) repulsion and dispersion attraction, an appreciable Intermolecular Bond stabilization by charge transfer is operative in D2 - CCl4. We also demonstrated that the present analysis is consistent with that carried out for the F(2P)-D2 and Cl(2P)-D2 systems, previously characterized by scattering experiments performed with state-selected halogen atom beams. A detailed comparison of the present and previous results on O2-CF4 and O2-CCl4 systems pinpointed striking differences in the behavior of hydrogen and oxygen molecules when they interact with the same partner, mainly due to the selectivity of the charge transfer component. The present work contributes to cast light on the nature and role of the Intermolecular interaction in prototype systems, involving homo-nuclear diatoms and symmetric halogenated molecules.
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molecular beam study of the ammonia noble gas systems characterization of the isotropic interaction and insights into the nature of the Intermolecular potential
Journal of Chemical Physics, 2011Co-Authors: Fernando Pirani, Luiz F Roncaratti, Leonardo Belpassi, Francesco Tarantelli, David CappellettiAbstract:We report new high resolution molecular beam experiments aimed at characterizing the Intermolecular interaction in the NH3–Ng (Ng = He, Ne, Ar, Kr, Xe) weakly bound complexes. Integral cross section data are obtained over a sufficiently wide velocity range and with rotationally hot NH3 molecules to produce (except for the NH3–He case) a well resolved “glory” quantum interference pattern. Data analysis, carried out by employing a recently proposed potential model, allows unique information on the absolute scale of the Intermolecular interaction to be obtained both at long range and at the equilibrium distance. An extensive and internally consistent comparison with the behavior of the corresponding Kr–Ng systems is exploited in order to identify those cases where an interaction component due to charge transfer effects provides an appreciable Intermolecular Bond stabilization that is clearly distinct from and must be added to the standard van der Waals plus induction picture. The results of the present investigation extend the phenomenology of perturbative charge transfer effects in gas phase complexes involving hydrogenated molecules.
Nicholas R Walker - One of the best experts on this subject based on the ideXlab platform.
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a chalcogen Bonded complex h3n s c s formed by ammonia and carbon disulfide characterised by chirped pulse broadband microwave spectroscopy
Journal of Chemical Physics, 2019Co-Authors: Eva Gougoula, Nicholas R Walker, Ibon Alkorta, Chris Medcraft, Anthony C. LegonAbstract:Ground-state rotational spectra were observed for ten symmetric-top isotopologues H3N⋯S=C=S, H3N⋯34S=C=S, H3N⋯S=C=34S, H3N⋯S=13C=S, H315N⋯S=C=S, H315N⋯34S=C=S, H315N⋯S=C=34S, H315N⋯S=13C=S, H315N⋯33S=C=S, and H315N⋯S=C=33S, the first five in their natural abundance in a mixture of ammonia and carbon disulphide in argon and the second group with enriched 15NH3. The four asymmetric-rotor isotopomers H2DN⋯S=C=S, H2DN⋯34S=C=S, H2DN⋯S=C=34S, and HD2N⋯S=C=S were investigated by using a sample composed of ND3 mixed with CS2. Rotational constants, centrifugal distortion constants, and 33S nuclear quadrupole coupling constants were determined from spectral analyses and were interpreted with the aid of models of the complex to determine its symmetry, geometry, one measure of the strength of the Intermolecular binding, and information about the subunit dynamics. The complex has C3v symmetry, with nuclei in the order H3N⋯S=C=S, thereby establishing that the non-covalent interaction is a chalcogen Bond involving the non-Bonding electron pair of ammonia as the nucleophile and the axial region near one of the S atoms as the electrophile. The small Intermolecular stretching force constant kσ = 3.95(5) N m−1 indicates a weak interaction and suggests the assumption of unperturbed component geometries on complex formation. A simple model used to account for the contribution of the subunit angular oscillations to the zero-point motion leads to the Intermolecular Bond length r(N⋯S) = 3.338(10) A.Ground-state rotational spectra were observed for ten symmetric-top isotopologues H3N⋯S=C=S, H3N⋯34S=C=S, H3N⋯S=C=34S, H3N⋯S=13C=S, H315N⋯S=C=S, H315N⋯34S=C=S, H315N⋯S=C=34S, H315N⋯S=13C=S, H315N⋯33S=C=S, and H315N⋯S=C=33S, the first five in their natural abundance in a mixture of ammonia and carbon disulphide in argon and the second group with enriched 15NH3. The four asymmetric-rotor isotopomers H2DN⋯S=C=S, H2DN⋯34S=C=S, H2DN⋯S=C=34S, and HD2N⋯S=C=S were investigated by using a sample composed of ND3 mixed with CS2. Rotational constants, centrifugal distortion constants, and 33S nuclear quadrupole coupling constants were determined from spectral analyses and were interpreted with the aid of models of the complex to determine its symmetry, geometry, one measure of the strength of the Intermolecular binding, and information about the subunit dynamics. The complex has C3v symmetry, with nuclei in the order H3N⋯S=C=S, thereby establishing that the non-covalent interaction is a chalcogen Bond involving the n...
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a two force constant model for complexes b m x b is a lewis base and mx is any diatomic molecule Intermolecular stretching force constants from centrifugal distortion constants dj or δj
Journal of Chemical Physics, 2016Co-Authors: Dror M Bittner, Nicholas R Walker, Anthony C. LegonAbstract:A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any diatomic molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M–X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJe or ΔJe, the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of Intermolecular Bond. For example, the Intermolecular Bond of B⋯MX can be a hydrogen Bond if MX is a hydrogen halide, a halogen-Bond if MX is a dihalogen molecule, or a stronger, coinage-metal Bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibri...