Jan Dillen

Preparing Gold(I) for Interactions with Proton Donors: The Elusive [Au]⋅⋅⋅HO Hydrogen Bond

MP2 and DFT calculations with correlation consistent basis sets indicate that isolated linear anionic dialkylgold(I) complexes form moderately strong (ca. 10 kcal mol(-1) ) Au⋅⋅⋅H hydrogen bonds with single H2 O molecules as donors in the absence of sterically demanding substituents. Relativistic effects are critically important in the attraction. Such bonds are significantly weaker in neutral, strong σ-donor N-heterocyclic carbene (NHC) complexes (ca. 5 kcal mol(-1) ). The overall association (>11 kcal mol(-1) ), however, is strengthened by co-operative, synergistic classical hydrogen bonding when the NHC ligands bear NH units. Further manipulation of the interaction by ligands positioned trans to the carbene, is possible.

The topology of the Coulomb potential density. A comparison with the electron density, the virial energy density, and the Ehrenfest force density

The topology of the Coulomb potential density has been studied within the context of the theory of Atoms in Molecules and has been compared with the topologies of the electron density, the virial energy density and the Ehrenfest force density. The Coulomb potential density is found to be mainly structurally homeomorphic with the electron density. The Coulomb potential density reproduces the non‐nuclear attractor which is observed experimentally in the molecular graph of the electron density of a Mg dimer, thus, for the first time ever providing an alternative and energetic foundation for the existence of this critical point.

A computational investigation of the effect of the double bond on the conformations of seven membered rings

The effect of the presence of an exo- and/or an endo double bond on the geometry of seven membered rings has been investigated by a conformational analysis of methylenecycloheptane, cycloheptamine, borepane, and 4-, 3- and 2-cyclohepten-1-one by the B3LYP/6-311+G(d,p) and CCSD(T)/6-311+G(d,p) levels of theory. The results indicate that both methylenecycloheptane and cycloheptamine have low energy barriers with respect to pseudorotation and a broad potential well centred on the most symmetrical twist-chair conformation. Borepane shows similar characteristics, but with drastically different relative energy values. The introduction of an extra endo double bond in the conformationally flexible cycloheptanone, fixes the family of chair conformations to a single rigid form, but lowers the relative energy of the boat conformations to compete in stability with the former.

Ligand-driven formation of halogen bonds involving Au(I) complexes

In a theoretical investigation at various levels of theory we show that even gold in the oxidation state +1 (i.e. formally positively charged) can behave as a Lewis base and, as a result, a halogen bond acceptor. Depending on the nature of the ligands in the gold complex the resultant halogen bonds are of similar strength to that found in the triiodide ion, but weaker than those involving the auride ion (highest value −59.4 kcal mol−1 for Au−·I2). The strength of the halogen bonds involving I2 range from −46.3 kcal mol−1 for the anionic adduct [((Me)2N)2Au]−·I2 to −5.9 kcal mol−1 for the cationic [(H3N)2Au]+·I2 adduct (calculated at the MP2/aug-cc-pVTZ-pp level of theory), and still weaker for adducts involving poorer halogen bond donors.

A comparison of energetic criteria to probe the stabilizing interaction resulting from a bond path between congested atoms: A Comparison of Energetic Criteria to Probe the Stabilizing Interaction Resulting from a Bond Path Between Congested Atoms

Four energetic criteria, all rooted in the partitioning of a molecule into atomic basins based on the properties of the electron density, are compared and correlated with the presence of a bond path between two nonbonded atoms in a series of sterically crowded derivatives of the same tetracyclododecane molecule. It was found that there is no correlation between the selected energetic criteria and the existence of a bond path between the congested atoms, nor with the existence of Ehrenfest force, virial, or Coulomb potential paths between those atoms.

Influence of the electrostatic environment on I3-···I3- and related I–M–I···I–M–I interactions

Non-covalent interactions in crystals are notoriously difficult to calculate accurately [1], due to the poor computational description of dispersion, which is often an important component of such interactions. This is particularly true for I3-•••I3interactions, which are observed in crystal structures despite the strong electrostatic repulsion between two negatively charged species [2]. Similarly, related metal-iodides exhibit I–M–I•••I–M–I interactions. In an effort to explain this phenomenon a thorough Cambridge Structural Database (CSD) analysis and theoretical study of the triiodide ion, metal-iodides and I•••I interactions within dimers of these species in a variety of environments is presented here. Optimisations in the gas phase and in an implicit polarisable continuum solvent model with several different solvents show that there is a significant dependence of the I3-•••I3interaction energy on the dielectric constant. The MP2/cc-pVTZ-pp level of theory comes closest to reproducing the I3bondlength and the I3-•••I3-intermolecular distance averages obtained from the Cambridge Structural Database (CSD). DFT methods are in general not as successful since they do not correctly model dispersion, however, the PBE method used in conjunction with Grimmes D2 dispersion correction [3] yields an interaction energy which is less than 2% from the CCSD/aug-cc-pVTZ-pp// MP2/cc-pVTZ-pp result. The Electrostatic Surface Potential (ESP) of the I3ion in the gas phase, chloroform, ethanol, water and n-methyl-formamide-mixture can be used as a gauge of the influence of the electrostatic environment on the properties of both the I3ion and the I3-•••I3interaction, or similarly I-M-I•••I-M-I interactions. This information can then be used to extrapolate to obtain a value for the strength of the I•••I inter-ion interaction energy in the solid state in a variety of complexes.

Single crystal structure and molecular dynamics analysis of a myo-inositol derivative

The crystal structure of 5-O-tert-butyldimethylsilyl-3,4-O-carbonyl-1,2-O-cyclohexylidene-2-oxo-3-oxa-4-bornanylcarbonyl-D-myo-inositol has been studied by single-crystal X-ray diffraction at both room temperature and 173 K. At room temperature, the tert-butyldimethylsilyl group exhibits dynamical disorder. A molecular dynamics simulation was used to model the disorder and this indicates that the group librates between two stable conformations in the crystal. Approximate relative energies of the different forms and energy barriers for the transition were obtained by empirical force field methods. Calculations of the thermal motion of the atoms are in good qualitative, but fair to poor quantitative agreement with the X-ray data.