Noncovalent Interactions оf Metal Complexes аnd Aromatic Molecules

Abstract

Our research is based on analyzing data in crystal structures from the Cambridge Structural Database (CSD) and on quantum chemical calculations. The analysis of the data from the CSD enable to recognize interactions in crystal structures and to describe the geometries of these interactions, while by quantum chemical calculations we can evaluate interaction energies and find the most stable interaction geometries. Using this methodology we were able to recognize and describe several new types of noncovalent interactions. Our study of planar metal-chelate rings interactions showed possibility of chelate ring stacking interactions with organic aromatic rings, and stacking interactions between two chelate rings. The calculated energies indicate strong stacking interactions of metal-chelate rings; the stacking of metal-chelate rings is stronger than stacking between two benzene molecules. Studies of interactions of coordinated water and ammonia indicate stronger hydrogen bonds and stronger OH/pi and NH/pi interactions of coordinated in comparison to noncoordianted water and ammonia. The calculations on OH/M interac-tions between metal ion in square-planar complexes and water molecule indicate that these interactions are among the strongest hydrogen bonds in any molecular system. The studies on aromatic molecules indicate stacking interactions at large horizontal dispacements between two aromatic molecules with significantly strong interacitons, the energy is 70% of the strongest stacking geometry. Our data also indicate that stacking interactions of an aliphatic rings with an aromatic ring are stonger than interactions between two aromatic molecules, while aliphatic/aromatic interactions are very frequent in protein structures.