Thomas A. Ford

The boron trifluoride–water complex. A preliminary matrix-isolation infrared spectroscopic and ab initio theoretical study

The infrared spectrum of boron trifluoride and water co-condensed in a nitrogen matrix at ca. 20 K has been recorded. A number of bands of a proposed 1:1 BF3⋯H2O electron donor–acceptor complex of Cs symmetry have been assigned. These assignments have been confirmed by a series of ab initio molecular-orbital calculations of the wavenumbers and intensities of the fundamental bands of the complex, using the GAUSSIAN-76 and GAUSSIAN-80 computer program packages and the 4-31G basis set. The spectra have been interpreted in terms of current theories of donor–acceptor complexes.

Ab initio molecular orbital calculations of the infrared spectra of interacting water molecules. Part 4. Interaction energies and band intensities of the complexes of water with carbon dioxide and nitrous oxide

Abstract The interaction energies and the infrared band intensities in the vibrational spectra of a number of different isomers of the binary complexes formed between water and carbon dioxide, and water and nitrous oxide, have been predicted by means of ab initio molecular orbital theory. The results are discussed in the light of our recently reported studies of the structures and the infrared band wavenumbers of these species, using the same theoretical approach.

The vibrational spectra of the boron halides and their molecular complexes. Part 4. Ab initio predictions of the structures and vibrational spectra of the complexes of boron trifluoride with dimethyl ether and dimethyl sulphide

Abstract The optimized structures and vibrational spectra of the 1:1 complexes of boron trifluoride with dimethyl ether and dimethyl sulphide have been determined by means of a series of ab initio calculations using the gaussian -90 computer program at the Hartree-Fock level with the 6–31G∗∗ basis set. The results have been rationalized on the basis of the interactions of the Lewis acid (BF3) with a hard ((CH3)2O) and a soft ((CH3)2S) base. The magnitudes of the wavenumber shifts, both for the acid and the base fragments, are far larger for the complex with the hard than with the soft base. The computed results have been used as aids in the interpretation of the infrared spectra of BF3 co-condensed with (CH3)2O and with (CH3)2S in cryogenic matrices, to be reported in a forthcoming publication.

The Vibrational Spectra of the Boron Halides and Their Molecular Complexes. 3. Ab Initio Predictions of the Structures, Energetics, and Mulliken Atomic Charges of the Complexes of Boron Trifluoride with Some Linear Nitrogen Donors

The structures of the 1:1 electron donor−acceptor complexes of boron trifluoride with a number of linear nitrogen bases (N2, N2O, HCN, FCN, C2N2, and HCCCN) have been optimized by means of a series of ab initio molecular orbital calculations, performed at the second order level of Moller−Plesset perturbation theory with the 6-31G** split-valence polarized basis set. The interaction energies have been computed and corrected for basis set superposition error and for zero-point energy difference. The Mulliken atomic charges of each atom have also been determined, and the changes on going from monomer to complex have been noted. The structural results are discussed in terms of the perturbation of the monomer properties (BF bond length and distortion from planarity) and the establishment of new complex properties (B···N bond length and FBN bond angle) on complexation. The structural changes and shifts of electronic charge, and the interaction energies, are correlated with the strengths of the interactions, est...

Ab initio calculations of the structural, energetic and vibrational properties of some hydrogen bonded and van der Waals dimers Part 3. The formaldehyde dimer

Abstract The structures, energies and atomic charges of five dimers of formaldehyde have been examined by means of ab initio molecular orbital theory, using the Gaussian-90 computer program at the second-order level of Moller-Plesset perturbation theory and the 6-31G split valence Gaussian basis set, augmented with polarization and diffuse functions (6-31++G ∗∗ ). These dimers are distinguished by the relative orientations of the monomer planes (coplanar, parallel or perpendicular) and dipoles (collinear, parallel or antiparallel). Three of the dimers were found to be genuine minima on the potential energy surface. These are a C s structure with its dipoles antiparallel and its molecular planes perpendicular; a coplanar species of C 2h symmetry with antiparallel monomer dipoles; and a C 21 . adduct with the dipoles collinear and the molecular planes perpendicular. The infrared spectra (wavenumbers and intensities) of these three dimers were computed, and the wavenumber shifts and intensity changes on dimerization were derived. The perturbations of these spectroscopic properties are compared with those observed for formaldehyde isolated in argon and nitrogen matrices at cryogenic temperatures, and the most probable structure is deduced in the light of all the available spectroscopic evidence.

The vibrational spectra of the boron halides and their molecular complexes: Part 7. Ab initio predictions of the infrared spectra of the complexes of boron trifluoride with some linear nitrogen donors☆

Abstract The infrared spectra of the 1:1 molecular complexes of boron trifluoride with five linear nitrogen-containing electron donors (nitrogen, hydrogen cyanide, cyanogen fluoride, cyanogen and cyanoacetylene) have been computed by means of a series of ab initio molecular orbital calculations, at the second order level of Moller–Plesset perturbation theory, using the 6-31G ∗∗ basis set. This work extends the calculations of the structures, energetics and Mulliken atomic charges of the same series of complexes, reported earlier. The vibrational properties, specifically the complex–monomer wavenumber shifts and the B⋯N stretching and BF 3 librational wavenumbers and their associated force constants, have been correlated with the computed interaction energies, corrected for basis set superposition error and for zero-point energy difference.

Ab initio molecular orbital studies of the vibrational spectra of some van der Waals complexes. Part 3: Complexes of carbon monoxide with carbon dioxide, nitrous oxide, carbonyl sulphide and carbon disulphide

Abstract The structures, interaction energies and vibrational spectra of four weak van der Waals complexes containing molecular nitrogen, as electron donor, and the linear triatomic molecules carbon dioxide, nitrous oxide, carbonyl sulphide and carbon disulphide, as electron acceptors, have been determined by carrying out a series of ab initio molecular orbital calculations using the Gaussian 98 computer program. The calculations were performed at the second order level of Moller-Plesset perturbation theory, employing the 6-311+G(d) basis set. The results have been interpreted by correlation with some molecular properties of the electron acceptors. The predicted spectra will be used as aids in the interpretation of the matrix isolation infrared spectra of the complexes determined experimentally.

Hydrogen bonds, improper hydrogen bonds and dihydrogen bonds

Abstract The structures, interaction energies and vibrational spectra of a large number of molecular complexes, formed by binary combination of the covalent hydrides of some of the elements of the first two rows of the periodic table, have been determined by means of ab initio molecular orbital theory at the MP2 level, using the 6-311++G(d,p) basis set. The results are discussed in terms of a variety of different types of interaction experienced by the monomer species as they undergo association, namely conventional hydrogen bonding, improper hydrogen bonding, dihydrogen bonding and electron donor–acceptor interaction.

The Fourier transform infrared spectra of the complexes of boron trifluoride with dimethyl ether and dimethyl sulphide in cryogenic matrices

Abstract The infrared spectra of boron trifluoride, co-condensed with dimethyl ether and with dimethyl sulphide in nitrogen and argon matrices at ca. 17 K, have been recorded. The spectra are consistent with the formation of 1:1 electron donor–acceptor molecular complexes, with donation occurring from the orbitals of the ether or the sulphide dominated by the oxygen or sulphur lone pairs to the orbital of boron trifluoride correlating with the empty axial 2p atomic orbital of boron. The wavenumber shifts of the respective monomer absorption bands have been determined in each matrix and correlated with the physical properties of the bases. The spectra may be rationalized by referring to the results of some molecular orbital calculations on these systems.

The Fourier transform infrared spectrum of the boron trifluoride-carbon dioxide complex

Abstract The Fourier transform infrared spectra from 4000 to 250 cm−1 of mixtures of boron trifluoride and carbon dioxide, trapped in nitrogen and argon matrices at cryogenic temperatures, have been recorded. Many bands have been assigned to a proposed 1:1 molecular complex, and the spectrum is consistent with the complex having an asymmetric top structure. This proposed structure is in agreement with the conclusions of an earlier gas phase molecular beam electric resonance study and with our own ab initio theoretical calculations.