Non-covalent interactions involving N-heterocyclic aromatic rings have recently received greater attention. They play an important role in many chemistry-related fields such as structures of biomolecules, the reactivity of molecules, crystal engineering, molecular recognition, and nanoengineering. Such rings, because of their distinctive electronic properties, are involved in different interaction patterns including π-stacking and hydrogen bonds. Hence, they are considered as useful recognition elements in many biological systems and became key components in most known drug molecules [1, 2].
Though some significant progress has been definitely made in the study of interactions involving N-heterocycles, most studies only focus on analyzing of stationary geometries and say nothing of a whole range of many other configurations. Accurate potential energy surfaces (PES) of such systems are not available and it is impossible to see how the stability of a particular system changes along with various geometrical parameters. Such maps, if they were present, would literally give a new way to look into the interactions patterns that may be formed.
For this reason, the extremely extensive analysis of potential energy surfaces of model N-heterocyclic dimers has been performed. The interaction energies of hundreds of thousands of dimers have been calculated. As the studied N-heterocycles the following ones have been selected: pyrrole, purine, pyridine, imidazole, pyrazole, 1,2,3-triazole, and 1,2,4-triazole. Since the interaction energies of a large number of systems were to be calculated, all the calculations have been carried out using a dispersion-corrected density functional. Other calculations, such as natural bond orbital and energy decomposition, have also been applied. The obtained results were then related to the statistical analysis made on the data gathered from Cambridge Structural Database .
The appliance of multidimensional analysis provides much deeper insight into the “landscape” of the interaction energies of the particular systems and enables one to see “a bigger picture” of what really occurs. The performed study, involving the combination of many different methods, has revealed the complexity of the formed intermolecular interactions. Apart from providing a “literal new look” into the present interaction patterns, another picture has emerged. Intermolecular interactions, especially stacking, present in the studied N-heterocycles, are seen” as a combination of many different sources of the interaction energy. The presented results may be a key importance in a prediction of crystal structures and may find a use in modeling of a crystal possessing desired properties.
Participation in this conference is financed by National Science Centre, Poland, 2017/01/X/ST4/00952