| Popis: |
The three novel lead(II) complexes, [Pb (L1) (NO3)2] (1), [Pb (L2) (NO3)2] (2), and [Pb (L3) (NO3)2] (3), were characterized by X-ray diffraction analysis. In order to understand the stereochemical structural nature and thermodynamic properties of these complex molecular systems, a theoretical study was conducted. The spatial coordinate positions of complex compounds 1–3 with lead were obtained from X-ray structural analysis and then used as initial coordinates to conduct density functional theory (DFT) theoretical calculations. This improved computational approach resulted in better accuracy when treating large, electron-rich species and better understanding of the complex compounds between the lariat crown ethers (LCEs) and lead ion. Through experimental data auxiliary of a quantum mechanical calculation approach, a DFT method was used to calculate the B3LYP/CEP-121G, B3LYP/SDD and B3LYP/LanL2DZ levels using the GAUSSIAN 03 package program. The calculations were conducted on the three novel LCEs complexed with lead ion. The theoretical calculation was to confirm the lowest energy, optimum geometric structure so as to receive more accurate thermodynamic properties and relative geometric stabilities of these three complex molecules. The atomic bond lengths, atomic torsion angles, binding energies and binding enthalpies of the three novel complex compounds were also calculated. The results of the DFT calculations show that these different complex compounds are cooperative participations of the oxygen on the C-pivot side arm with the ring oxygen molecules to form a six coordination number ligand of stable lead complex compound, which was also confirmed by the single crystal X-ray crystallography analysis. |
Full Text from ScienceDirect