The influence of water molecules on NdCl3·3C3H8O in the properties: A DFT study

Abstract

The catalytic activity of NdCl3-ROH-AlR3 is closely related to the amount of water in NdCl3. Usually NdCl3·6H2O has been dehydrated step by step to NdCl3·2H2O, however, the further dehydration process will be very difficult. In this work, we investigated the effect of added water molecules on structures and properties of NdCl3·3C3H8O, NdCl3·3C3H8O·H2O, and NdCl3·3C3H8O·2H2O, including bond length, angle, mulliken atomic charge, molecular electrostatic potential (MEP), HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) energy, and natural bond orbital (NBO). All properties were calculated by density functional theory (DFT) using B3PW91 functional and basis set of 6-31G++**/SDDALL. It was found that the bond length of NdCl bond and bond angles of Cl3-NdCl2, O9-NdO5, Cl3-NdCl4 could be directly affected due to the addition of water molecule. The MEP analysis revealed that the molecular reaction site should be located around Cl atom. Furthermore, analysis of mulliken atomic charges showed that charge of Nd atom as the active center of the reaction changed from 0.956 to 1.238 and then to 1.301 after addition of one water molecule and two water molecules respectively. HOMO and LUMO orbitals were carried out to investigate the stability of the system, the addition of two water molecules in the system enhanced the electron flow in the system. Also, NBO analysis was further performed to supply an in depth insight into the electronic structure, the distribution of valence electrons and bond orders, which all changed after the addition of water molecule. Therefore, it was necessary to convert NdCl3·2H2O to NdCl3 in order to achieve a higher catalytic activity.