Crystal engineering via C-H...F and C-H...pi interactions in two substituted indoles

Area of Science:

• Crystallography
• Organic Chemistry
• Materials Science

Background:

• Understanding intermolecular interactions is crucial for crystal engineering.
• Fluorine substitution can significantly influence molecular packing and properties.
• Tetrahydroindole derivatives are scaffolds with potential applications in various fields.

Purpose of the Study:

• To elucidate the crystal structures of two novel fluorophenyl-substituted tetrahydroindoles.
• To investigate the role of 'organic fluorine' in directing crystal packing.
• To analyze the specific intermolecular interactions, such as C-H...F and C-H...pi bonds, present in the crystal lattices.

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the three-dimensional crystal structures.
• Structural analysis focused on identifying and quantifying intermolecular interactions.
• Comparative analysis of the two structures was performed to highlight the effect of structural modifications (dimethyl substitution).

Main Results:

• The crystal structures of 1-(4-fluorophenyl)-2-phenyl-4,5,6,7-tetrahydro-1H-indole (C20H18FN) and 1-(4-fluorophenyl)-6,6-dimethyl-2-phenyl-4,5,6,7-tetrahydro-1H-indole (C22H22FN) were successfully determined.
• Both compounds exhibit distinct molecular packing motifs in the solid state.
• Weak interactions, including C-H...F hydrogen bonds and C-H...pi interactions, were identified as key stabilizing forces in the crystal structures.

Conclusions:

• Organic fluorine plays a significant role in dictating molecular arrangement within crystal structures.
• The presence and positioning of fluorine atoms influence the formation of specific intermolecular interactions.
• The study provides valuable insights into crystal engineering strategies utilizing weak interactions for designing functional organic materials.