The terms tetrel bond, pnictogen bond and chalcogen bond were coined recently to describe non-covalent interactions involving group 14, 15 and 16 atoms, respectively, acting as the electrophilic site that seeks a nucleophilic region of another molecule, for example a non-bonding electron pair or π-electron pair of a Lewis base Many complexes containing these non-covalent bonds were identified and characterised in isolation in the gas phase by rotational and vibrational spectroscopy long before they were given these names In this article, the geometries so determined for selected examples of complexes of each type are rationalised in terms of the molecular electrostatic surface potentials of the component molecules Examples of chalcogen-bonded complexes considered are based mainly on sulfur dioxide, with the region near the sulfur atom as the electrophilic site that interacts with n-electron and π-electron pairs for a range of simple Lewis base molecules For tetrel bonds, the examples discussed involve the carbon atom of carbon dioxide as the electrophilic centre, while for pnictogen bonds the central nitrogen of the closely related molecule nitrous oxide is chosen Geometrical similarities within each series allow simple definitions of each type of non-covalent bond that are conformal with that recently advanced for the halogen bond, a related non-covalent interaction

Tetrel, pnictogen and chalcogen bonds identified in the gas phase before they had names: a systematic look at non-covalent interactions

We have optimized the lowest energy structures and calculated interaction energies for the CO2–Ar, CO2–N2, CO2–CO, CO2–H2O, and CO2–NH3 dimers with the recently developed explicitly correlated coupled cluster singles doubles and perturbative triples [CCSD(T)]-F12 methods and the associated VXZ-F12 (where X = D,T,Q) basis sets. For a given cardinal number, we find that results obtained with the CCSD(T)-F12 methods are much closer to the CCSD(T) complete basis set limit than the conventional CCSD(T) results. The relatively modest increase in the computational cost between explicit and conventional CCSD(T) is more than compensated for by the impressive accuracy of the CCSD(T)-F12 method. We recommend use of the CCSD(T)-F12 methods in combination with the VXZ-F12 basis sets for the accurate determination of equilibrium geometries and interaction energies of weakly bound electron donor acceptor complexes.

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Explicit correlation and intermolecular interactions: investigating carbon dioxide complexes with the CCSD(T)-F12 method.

CO/MgO(001) at different CO coverages: a periodic ab initio Hartree-Fock and B3-LYP study

A procedure is proposed to produce intermolecular potential energy surfaces from limited data. The procedure involves generation of geometrical configurations using a Latin hypercube design, with a maximin criterion, based on inverse internuclear distances. Gaussian processes are used to interpolate the data, using over-specified inverse molecular distances as covariates, greatly improving the interpolation. Symmetric covariance functions are specified so that the interpolation surface obeys all relevant symmetries, reducing prediction errors. The interpolation scheme can be applied to many important molecular interactions with trivial modifications. Results are presented for three systems involving CO2, a system with a deep energy minimum (HF - HF) and a system with 48 symmetries (CH4 - N2). In each case the procedure accurately predicts an independent test set. Training this method with high-precision ab initio evaluations of the CO2 - CO interaction enables a parameter-free, first-principles prediction of the CO2 - CO cross virial coefficient that agree very well with experiments.

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Interpolation of intermolecular potentials using Gaussian processes

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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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

Two techniques have been used to observe the spectrum of a weakly bound dimer (CO2, CO) formed in a pulsed jet of CO2 and CO seeded in argon. The v=1←0 vibrational transition in the modified asymmetric stretching mode of the CO2 subunit was first observed at Doppler‐limited resolution by investigating the pulsed jet with an infrared diode‐laser spectrometer. Then the ground‐state pure rotational spectrum was detected by applying Fourier‐transform microwave spectroscopy to such a jet. A combined fit of the two spectra of the parent isotopomer gave the following set of ground‐state (v=0) and excited‐state (v=1) spectroscopic constants: A0=11 863.48(56) MHz, B0=1883.915(4) MHz, C0=1613.297(4) MHz, A1=11 772.17(37) MHz, B1=1882.76(6) MHz, C1=1611.44(5) MHz, ΔJ =8.145(2) kHz, ΔJK =339.42(1) kHz, δJ =1.26(1) kHz, and δK =309.8(4) kHz when the centrifugal distortion constants were constrained to be equal in both states. Spectroscopic constants for the isotopomers (CO2, 13CO) and (CO2, C18O) have also been determ...

A. P. Suckley

Papers

Infrared diode‐laser spectroscopy and Fourier‐transform microwave spectroscopy of the (CO2,CO) dimer in a pulsed jet