Hoogsteen–Watson–Crick 9-Methyladenine:1-Methylthymine Complex: Charge Density Study in the Context of Crystal Engineering and Nucleic Acid Base Pairing

Abstract

This study provides a detailed charge density distribution analysis supported by comprehensive energetic investigations. The nature of the intermolecular interactions existing in the 9-methyladenine:1-methylthymine cocrystal structure with respect to those specific for the corresponding monocomponent crystals is explored. Charge density topological investigations lead to reliable hydrogen-bond interaction energies consistent with the results of the DFT approach with Grimme dispersion correction applied. The cocrystal structure cohesive energy corresponds with the average stability of its components’ crystals. This is in agreement with the experimental observations. Thus, formation of the particularly strong 9-methyladenine:1-methylthymine motif (interaction energy around −70 kJ·mol–1, DFT(B3LYP)/pVTZ, BSSE and dispersive corrections applied) may constitute the driving force for cocrystal growth. All three systems form molecular layers governed by hydrogen-bond interactions whereas interacting mostly dispe...