Quantitative analysis of solid-state diversity in trifluoromethylated phenylhydrazones.

Abstract

The cooperative roles of various structural motifs associated with the presence of different intermolecular interactions in the formation of molecular crystals are investigated in a series of trifluoromethylated phenylhydrazones. Out of the six compounds analysed, two exhibit three-dimensional structural similarities with geometrically equivalent building blocks, while a third exists as two polymorphic forms crystallized from ethanol solutions at low temperature (277 K) and room temperature (298 K), respectively. The compounds were characterized via single-crystal and powder X-ray diffraction techniques and differential scanning calorimetry. In the absence of any strong hydrogen bonding, the supramolecular constructs are primarily stabilized via molecular pairs with a high dispersion-energy contribution, due to the presence of molecular stacking along the molecular backbone along with C-H...π interactions in the solid state, in preference to an electrostatic contribution. The interaction energies for the most stabilizing molecular building blocks are in the range -29 to -43 kJ mol-1. In addition, weak N-H...F, C-H...F and N-H...C interactions and F...F, F...C, F...N and C...N contacts act as secondary motifs, providing additional stability to the crystal packing. The overall molecular arrangements are carefully analysed in terms of their nature and energetics, and the roles of different molecular pairs towards the crystal structure are delineated. A topological study using the quantum theory of atoms in molecules was used to characterize all the atomic interactions in the solid state. It established the presence of (3, -1) bond critical points and the closed-shell nature of all the interactions.