Through Space and Through Bonds 2e-3c bonding interactions

LOBAYAN, ROSANA M. ; BOCHICCHIO, ROBERTO

Granada

Congreso; XXXIX International Congress Theoretical Chemists of Latin Expression; 2013

Universidad de Granada

The description of electron distributions in molecular systems found the onset of complex patterns of bonding, as for instance charge shift bonds, agnostic bonds, 2e-3c bonds, between others, where may be the last one is the most difficult to describe. The local and non-local topological treatments applied to the density decomposition into its respectively paired and unpaired contributions constitutes a powerful technique for the aforementioned description and may be considered as the quantum version of Lewis conjecture of classical bonding patterns of pairing.1-4 Consequently, this technique permitted to establish a quantum rule for detecting and determining the strength of the multi-center patterns of bonding.The analysis is mainly focused on the nature of each of the bonding character (interaction) within the molecular structure. It is carried out by the determination of the critical points of each of the contributions to the density, the local accumulation or depletion of each field and the maps at the neighborhood and surroundings of these points. Also the descriptors, i.e., magnitudes describing the classical ideas of chemistry (integrated or non local) as for instance, covalent bond orders, valence, free valence (hole or unpairing electron populations), 2e-3c populations, among others are determined. Therefore, all this information as a whole, captured from the state-function, performs an accurate description. The description of several compounds differing in nature and type of bonding gave us a deep experience about the electron distribution at the mentioned situations. We will deal in the present case with the 2e-3c bonding character of some new selected systems (not treated early) to exemplify an interesting situation of two types of interactions appearing in these type of systems, which allow us to interpret the above mentioned pattern and to understand the physical meaning of the rule. The main result seems to indicate that the rule bifurcate into two type of interaction preserving the 2e-3c pattern of bonding, i.e., through space (TS) and through bonds (TB). The common trend of both types of this pattern is that the 2e-3c populations are appreciable but the electron cloud is localized in different parts of space regarding the nucleus positions. These considerations may be considered as a bifurcation of the quantum rule that permits to classify this complex pattern of bonding into the two types mentioned.