Structural, vibrational and electronic properties of some tetrel-bonded complexes of the fluorinated methanes methyl fluoride, difluoromethane and fluoroform: an ab initio study.

A search has been conducted, by means of ab initio molecular orbital theory, for potential tetrel-bonded complexes formed between the fluorinated methanes methyl fluoride, difluoromethane and fluoroform, and the related hydrides ammonia, water, hydrogen fluoride, phosphine, hydrogen sulphide and hydrogen chloride. Eleven such complexes have been identified, six containing CH3F and five CH2F2. The complexes are typically less strongly bound than their hydrogen-bonded counterparts, and the interaction energies vary in a consistent way with the periodic trend of the electron donors. The intermolecular separations and changes of the relevant intramolecular bond lengths, the wavenumber shifts of the critical vibrational modes and the extents of charge transfer correlate, by and large, with the strengths of interaction.

The Structures, Molecular Orbital Properties and Vibrational Spectra of the Homo- and Heterodimers of Sulphur Dioxide and Ozone. An Ab Initio Study.

The structures of a number of dimers of sulphur dioxide and ozone were optimized by means of a series of ab initio calculations. The dimer species were classified as either genuine energy minima or transition states of first or higher order, and the most probable structures consistent with the experimental data were confirmed. The molecular orbitals engaged in the interactions resulting in adduct formation were identified and relations between the orbitals of the dimers of the valence isoelectronic monomer species were examined. The vibrational spectra of the most probable structures were computed and compared with those reported in the literature, particularly with spectra observed in cryogenic matrices. The calculations were extended to predict the properties of a number of possible heterodimers formed between sulphur dioxide and ozone.

Structural, energetic, and vibrational properties of the homodimers of the silyl, germyl, and stannyl halides, (MH3X)2 (M = Si, Ge, Sn; X = F, Cl, Br, I).

A number of properties of the homodimers of the three families of molecules MH3X, where M is Si, Ge, and Sn and X is F, Cl, Br, and I are computed. The results are compared with those of a similar study of the homodimers of the methyl halides containing the same four halogen atoms, and some notable differences are observed among related sets of monomer species. The interaction energies, the primary intermolecular geometrical parameters, the changes in the intramolecular bond lengths, and the vibrational data (wavenumber shifts and dimer/monomer infrared intensity ratios) of some of the modes most closely associated with the site of interaction show, for the most part, regular variations as the central atom and the halogen atom are systematically varied. The results are interpreted in terms of the changes in the bonding properties of the monomer molecules as they undergo dimerization. Graphical abstract Interaction energies of the silyl, germyl and stannyl fluoride, chloride, bromide and iodide dimers.

Chalcogen-bonded complexes. Selenium-bound adducts of NH3, H2O, PH3, and H2S with OCSe, SCSe, and CSe2.

Recent ab initio investigations of some complexes formed between carbon dioxide and its analogues carbonyl sulfide, carbonyl selenide, carbon disulfide, and thiocarbonyl selenide and the common bases ammonia, water, phosphine, and hydrogen sulfide have revealed significant differences between the properties of those complexes bound through the oxygen atom of the electron acceptor and their counterparts in which the interaction takes place through a sulfur atom. In each case the interaction is weak, but the structures, interaction energies, and vibrational spectra of the complexes show some regular variations in behavior as the base and the acid are systematically changed. The adducts bound through sulfur present examples of the type of non-covalent interaction known as the chalcogen bond. In this paper we extend the range of electron acceptors to include carbon diselenide, and we explore the effects of substituting selenium for sulfur as the acceptor atom in the complexes of OCSe, SCSe, and CSe2. These adducts are also classified as chalcogen-bonded complexes, and have many features in common with the sulfur-bonded species, but also exhibit some noticeable differences between the two series.

Vibrational spectra of the boron halides and their molecular complexes. Part 11. Complexes of boron trifluoride with phosphine and its methyl derivatives. An ab initio study.

Ab initio calculations, at the second-order level of Møller-Plesset perturbation theory, using a triple-zeta Gaussian basis set with polarization and diffuse functions on all atoms, have been carried out on the donor-acceptor complexes of boron trifluoride with phosphine and its mono-, di-, and trimethyl derivatives. The structures, interaction energies, and vibrational spectra of the complexes were determined. The preferred conformer was found to be the staggered species in each case. The computed data were compared with those for some similar complexes containing boron trifluoride and a series of related oxygen, sulfur, and nitrogen bases, and the effect of successive methyl substitution in each series was investigated.

The vibrational spectra of the boron halides and their molecular complexes Part 10. The complexes of boron trifluoride with ammonia and its methyl derivatives. An ab initio study.

Ab initio calculations, at the level of second order Møller-Plesset perturbation theory, and using a triple-zeta Gaussian basis set with polarization and diffuse functions on all atoms, have been carried out on the donor-acceptor complexes of boron trifluoride with ammonia and its mono-, di- and trimethyl derivatives. The structures, interaction energies and vibrational spectra of the complexes have been determined. An eclipsed and a staggered conformer have been examined for each complex, and the preferred conformer was found to be the staggered species in each case. The computed data have been compared with those for some similar complexes containing boron trifluoride and a series of oxygen and sulphur electron donors (water, hydrogen sulphide, methanol, methanethiol, dimethyl ether and dimethyl sulphide) and the effect of successive methyl substitution in all three series has been investigated.

The structures of some trimers of carbon monoxide--an infrared matrix isolation spectroscopic and ab initio molecular orbital study.

Using a number of potential models for the gas-phase structure of the trimer of carbon monoxide as a guide, ab initio molecular orbital calculations have been carried out on this aggregate in order to determine its probable structure and vibrational spectrum in cryogenic matrices. The Fourier transform infrared spectra of carbon monoxide trapped in argon and nitrogen matrices have been recorded and, on the basis of the results of the theoretical calculations, a search for possible absorptions which may be assigned to trimeric species has been undertaken.

Ab initio molecular orbital studies of the vibrational spectra of the van der Waals complexes of boron trifluoride with the noble gases.

The molecular structures, interaction energies, charge transfer properties and vibrational spectra of the van der Waals complexes formed between boron trifluoride and the noble gases neon, argon, krypton and xenon have been computed using second and fourth order Møller-Plesset perturbation theory and the Los Alamos National Laboratory LANL2DZ basis set. The complexes are all symmetric tops, with the noble gas atom acting as a sigma electron donor along the C3 axis of the BF3 molecule. The interaction energies are all vanishingly small, and the amount of charge transferred in each case is of the order of 0.01e. The directions of the wavenumber shifts of the symmetric bending (nu2) and antisymmetric stretching (nu3) modes of the BF3 fragment confirm those determined experimentally, and the shifts are shown to correlate well with the polarizability of the noble gas atom and the inverse sixth power of the intermonomer separation. The nu2 mode is substantially more sensitive to complexation than the nu3 vibration.