Adjusting the physical and chemical properties of crystalline materials by controlling their structures is highly desirable in solid-state and materials chemistry. Such control can be achieved by carefully exploiting and fine-tuning the interactions between molecules. In this work, functionalized benzochalcogenadiazole molecules capable of forming two different σ-hole interactions (halogen and chalcogen bonds) are used as building blocks to assemble crystals with distinctly different structural features. Ab initio calculations are performed in order to rationalize the crystal structures obtained and to quantify the intermolecular interactions. It is found that the structural features and the balance between different interactions, as well as the relative strength of the σ-hole interactions, are highly sensitive to the identity of the halogen and chalcogen atoms in the molecules. Both electrostatic/polarization and dispersion forces play an important role in defining the energetics of the chalcogen-bonded and halogen-bonded isomers, and by a control of the balance between these components, it is possible to precisely control the point at which one type of supramolecular architecture is favored over another.

Explicit solvent interactions can significantly alter the physical and chemical properties of noble metal (e.g., gold and silver) nanoclusters. In order to compute these solvent interactions at a reasonable computational cost, a quantum mechanical (QM)/molecular mechanics (MM) approach, where the metal nanocluster is treated with full QM and the water molecules are treated with a MM force field, can be used. However, classical MM force fields were typically parameterized using molecules containing main group elements as the reference. The accuracy of noble metal–solvent interactions obtained with these force fields therefore remains unpredictable. The effective fragment potential (EFP) force field, designed to model explicitly solvated systems, represents an attractive method to simulate solvated noble metal nanoclusters because it is derived from first principles and contains few or no fitted parameters, depending on implementation. At the density functional theory-optimized geometries, good correlation is obtained between the nanocluster–water interaction energies computed with EFP and those computed with the reference coupled cluster singles, doubles, and perturbative triples method. It is shown that the EFP method gives qualitatively accurate interaction energies at medium–large intermolecular distances for various molecular configurations. In order to achieve higher quantitative accuracy, the first solvation shell should be treated with full QM, if possible. EFP is therefore a promising method for the QM modeling of explicitly solvated silver and gold nanoclusters.