Predicting the Magnitude of σ-holes Using VmaxPred, a Fast and Efficient Tool Supporting the Application of Halogen Bonds in Drug Discovery.

Halogen bonding as a modern molecular interaction has received increasing attention not only in materials sciences but also in biological systems and drug discovery. Thus, there is a growing demand for fast, efficient, and easily applicable tailor-made tools supporting the use of halogen bonds in molecular design and medicinal chemistry. The potential strength of a halogen bond is dependent on several properties of the sigma-hole donor, e.g., a (hetero)aryl halide, and the sigma-hole acceptor, a nucleophile with n or pi electron density. Besides the influence of the interaction geometry and the type of acceptor, significant tuning effects on the magnitude of the sigma-hole can be observed, caused by different (hetero)aromatic scaffolds and their substitution patterns. The most positive electrostatic potential on the isodensity surface (V-max), representing the sigma-hole, has been widely used as the standard descriptor for the magnitude of the sigma-hole and the strength of the halogen bond. Calculation of V-max using quantum-mechanical methods at a reasonable level of theory is time-consuming and thus not applicable for larger numbers of compounds in drug discovery projects. Herein we present a tool for the prediction of this descriptor based on a machine-learned model with a speedup of 5 to 6 orders of magnitude relative to MP2 quantum-mechanical calculations. According to the test set, the squared correlation coefficient is greater than 0.94.