Host-guest interaction based on Morokuma-Ziegler analysis
The analysis of host-guest interactions based on the Morokuma-Ziegler decomposition scheme has proven successful procedure for interpretation of the nature of the interaction between the two structures. In the case of MOFs, analysis of the interaction has recently been reported, considering the MOF and the guest as the two molecular fragments that constitute the whole system.33-35
From this perspective, the energy decomposition analyses (EDA) was carried out, where each system studied was divided into two fragments: Zn-MOF and the analyte (i.e . nitrobenzene and toluene). Due to our interest in the dispersive forces (van der Waals force) acting between the fragments [Zn-MOF] and [analyte], were incorporating Grimme’s (D3) dispersion correction this analysis. According to the results, interaction energies for all systems does not exceed -6 kcal/mol, which indicates the predominant the long-range interactions. The Zn-MOF-analyte interactions are more intense in the case of analytes more electron-deficient (i.e. nitrobenzene), for which electrostatic interaction represents 51% of interaction energy. While the toluene, containing the electron-donating group, shows that weaker interaction energy with Zn-MOF, in which the dispersive contribution represents 67 %, see Table 3. These results evidence that in the case of the Zn-MOF-nitrobenzene is possible a charge transfer between the Zn-MOF and nitrobenzene.
Table 3. Morokuma–Ziegler’s scheme energy decomposition analysis (EDA kcal/mol) of denoting the Zn-MOF-analyte interaction.