The topology of the molecular electron density of benzene dithiol gold cluster complex Au4−S−C6H4−S′−Au′4 changed when relativistic corrections were made and the structure was close to a minimum of the Born–Oppenheimer energy surface. Specifically, new bond paths between hydrogen atoms on the benzene ring and gold atoms appeared, indicating that there is a favorable interaction between these atoms at the relativistic level. This is consistent with the observation that gold becomes a better electron acceptor when relativistic corrections are applied. In addition to relativistic effects, here, we establish the sensitivity of molecular topology to basis sets and convergence thresholds for geometry optimization.

The reductive coupling of an NHC-stabilized aryldibromoborane yields a mixture of trans-and cis-diborenes in which the aryl groups are coplanar with the diborene core. Under dilute reduction conditions two diastereomers of a borirane-borane intermediate are isolated, which upon further reduction give rise to the aforementioned diborene mixture. DFT calculations suggest a mechanism proceeding via nucleophilic attack of a dicoordinate borylene intermediate on the aryl ring and subsequent intramolecular B-B bond formation.

We present a theoretical study on the role of van der Waals (vdW) interactions on the structure and, as a consequence, the photoinduced charge separation (CS) of a series of dimer complexes formed by the polymer P3HT and the fullerene derivative PCBM. CS rate constants for P3HT/PCBM dimer structures in which vdW interactions are taken into account agree well with experimental data. Without proper treatment of vdW interactions during geometry optimizations, the predicted CS rates can be too low by up to 3 orders of magnitude. These variations in computed CS rates are not due to changes in the Gibbs energy for CS. Instead, the electronic coupling increases by up to 2 orders of magnitude for structures obtained with dispersion-corrected density functionals that lead to deformations in the P3HT oligomer with pronounced π–π stacking interactions with PCBM.

Boron-boron multiple bonds, such as those found in diborenes and diborynes, are typically stabilized by σ-donor ligands that furnish electron density to these otherwise electron-deficient species. These compounds are not only of fundamental importance in the study of chemical bonding, but can also activate small molecules in a chemistry reminiscent of that carried out by transition metals. In the pursuit of designing new and improved σ-donor ligands to stabilize diborenes and diborynes suitable to activate small molecules, we performed density functional calculations to evaluate the Lewis basicity of a series of σ-donor ligands. For this evaluation, we analysed the interaction between the boranes and the σ-donor ligands in model systems L!BX 3 (X=F and Me) using energy decomposition analyses. We found that electronic bond energies of the L!BX 3 adducts correlate well with the ionization energies of the ligands and that ligands with high or medium basicity stabilize diborynes better than ligands with low basicity. We also learnt that beryllium-based ligands are promising since they are able to stabilize L!B�B ! L diborynes without significantly reducing the triple bond character of the B�B bond.