N-Methylated Nucleobases Crystal Structures and π-π Stacking Interactions

Area of Science:

• Solid-state chemistry
• Crystallography
• Molecular structure

Background:

• Intermolecular geometries of methylated nucleobases in the solid state are not well-documented.
• Methylated purines are significant in biological systems and drug development.

Purpose of the Study:

• To systematically investigate the solid-state structures of 1-, 3-, and 7-methylated adenines and guanines.
• To analyze hydrogen bonding and pi-pi stacking interactions in these methylated nucleobases.

Main Methods:

• Single-crystal X-ray diffraction
• Synchrotron/laboratory X-ray powder diffraction (XRPD)
• In situ high-temperature XRPD
• Differential thermal analysis/thermogravimetry (DTA/TG)

Main Results:

• Crystal structures of methylated adenines and guanines, including hydrates, were determined.
• High-temperature XRPD and DTA/TG revealed water removal effects and a new polymorph for 3-methyladenine.
• Hydrogen bonding forms ribbon planar or linear double-bonded motifs.
• Pi-pi stacking interactions align with theoretical predictions for N-methylated purine bases.

Conclusions:

• This research provides the first systematic experimental data on the solid state of these methylated purine compounds.
• The findings enhance understanding of nucleobase interactions in crystalline environments.
• The study validates theoretical models for pi-pi stacking in N-methylated purines.