Perspectives of Halogen Bonding Description in Scoring Functions and QSAR/QSPR: Substituent Effects in Aromatic Core

Halogen bonding (XB) is a new promising interaction pattern in medicinal chemistry. It has predominantly electrostatic nature - high electrostatic potential anisotropy. However to fully unleash the potential of XB in rational drug design fast and robust empirical methods of XB description should be developed. Current approaches rely heavily on ab initio calculation for each molecule studied. Thus fast prediction of electrostatic parameters for description of XB for arbitrary organic molecules is of paramount importance to promptly establish QSAR/QSPR, virtual screening and molecular docking pipelines suitable for today's agile development requirements. The two most promising approaches to describe anisotropic electrostatic models - the extra point (EP) charge model and the multipole expansion (ME) model - were studied on their ability (1) to describe ab initio molecular electrostatic potential (MEP) and (2) to produce parameters that can be predicted for each molecule empirically rather than estimated via ab initio calculations. The reference ab initio MEP was calculated for a set of 730 substituted halobenzenes. Parameters for anisotropic electrostatics of both empirical models (EP and ME) studied were extracted from ab initio MEP. The FreeWilson and Hansch type QSPR models relating XB parameters with aromatic substituents were built and analyzed, providing the guidelines for further development.