Ab initio prediction of plausible conformers of a flexible N-(3-chloro-4-fluorophenyl)thiourea (CFT) molecule: A validation study

Abstract

The current aim of the ab initio crystal structure prediction is to find the possible conformers of the flexible N-(3-chloro-4-fluorophenyl)thiourea (CFT) molecule using gas phase optimization with an MP2/6-31G(d,p) basis set, and the lattice energy minimization in the presence of a repulsion-dispersion electrostatic potential. If the molecule deviates from the gas phase conformation, suitable intermolecular interactions are added, and the molecule favours stable packing. The crystal structure is said to be feasible if the intermolecular lattice energy compensates the intermolecular energy penalty associated with the suboptimal gas phase conformers. The idea of the current research is to find the least energy hydrogen bonded crystal structure from a set of rigid conformers in a conformation region, with a significant similarity of packing, which may lead to the prediction of polymorphs associated with the considered CFT molecule.