Hydrogen Bonding in Chloro- and Hydroxy-7-Azaindoles: Insights from X-Ray, Vibrational Spectroscopy, and DFT Studies

Area of Science:

• Solid-state chemistry
• Molecular spectroscopy
• Computational chemistry

Background:

• Understanding intermolecular interactions is crucial for designing materials with specific properties.
• Azaindole derivatives are important scaffolds in medicinal chemistry and materials science.
• The influence of ring substituents on hydrogen bonding and crystal packing requires detailed investigation.

Purpose of the Study:

• To investigate how substituents on the azaindole ring affect intermolecular hydrogen bonding and crystal packing.
• To correlate structural findings with vibrational spectra.
• To elucidate the role of DFT calculations and Hirshfeld analysis in understanding these interactions.

Main Methods:

• Single-crystal X-ray diffraction for crystal structure determination.
• Fourier-transform infrared (FT-IR) and Fourier-Raman (FT-Raman) spectroscopy for vibrational analysis.
• Density functional theory (DFT) calculations (B3LYP-D3, ωB97X-D) and Hirshfeld surface analysis.

Main Results:

• Halogenated azaindoles (5Cl7AI, 4,5Cl7AI) form linear N-H···N hydrogen-bonded dimers or layers.
• 5-hydroxy-7-azaindole (5OH7AI) forms a 3D network via N-H···O and O-H···N interactions.
• Vibrational spectra show distinct N-H and O-H stretching bands correlating with hydrogen bond topology and linearity.

Conclusions:

• Ring substituents profoundly modulate hydrogen bonding and molecular assembly in azaindoles.
• DFT and Hirshfeld analyses effectively complement experimental data for structural and vibrational insights.
• The study provides a detailed understanding of structure-property relationships in substituted azaindoles.