Solvent effect on the shielding tensor and coupling constant calculations of platinum(III) dinuclear complexes investigated by ab initio molecular dynamic

Author(s)

Patrick Rodrigues Batista

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2022-02-14

Examining board members

Lucas Colucci Ducati; Antonio Carlos Borin; Kaline Rabelo Coutinho; Cláudio Francisco Tormena

• Advisor: Lucas Colucci Ducati

Abstract

The present thesis addresses the analysis of the dynamic effect of the water solvent on the indirect spin-spin coupling constant 1JPtPt and on the shielding tensor (σ195Pt)/chemical shift (δ195Pt) of a series of platinum(III) dinuclear complexes [L— Pt2(NH3)4(Am)2— L]4+ with different amidate bridging ligands (Am = α-pyridonate; α-pyrrolidonate; pivalamidate) and axial ligands (L = H2O, Cl¯ e Br¯). The conformational dynamic and configuration sampling were carried out using realistic simulations combining Car-Parrinello ab initio molecular dynamics (CPMD) and relativistic calculations of 1JPtPt and δ195Pt in the density functional theory (DFT) framework. The J-coupling was decomposed into natural localized molecular orbitals (NLMO). These analyses allowed to describe the solute-solvent interactions and to quantify the direct, indirect, and polarization effects of the solvent on magnetic properties. The findings showed that the theoretical parameters computed with static geometries at DFT level, including the implicit solvente effect and relativistic correction, are overestimated regarding the experimental values up to 100% for the diaqua (L = 2H2O) complexes. For aquahalo (L = H2O; X¯) and dihalo (L = 2X¯) complexes, the values obtained at this same level of theory presented a good precision. The indirect solvent effect (via structural changes) had a dramatic effect on the 1JPtPt and the complexes exhibit a strong trans influence in solution, where the Pt— Pt bond lengthens with increasing axial ligand σ-donor strength. The results using the CPMD configurations to calculate the magnetic properties were quite accurate, especially for diaqua derivatives which showed the highest sensitivity to the solvent effect. It was found that 10 explicit solvent molecules along with the implicit conductor-like screening model (COSMO) method are important for a good description of the complexes in solution and to calculate the 1JPtPt. The δ195Pt also show a good improvement when calculated at the CPMD framework, but in some cases the theoretical results with static geometries including COSMO also showed satisfactory agreement with experiment. The NLMO decomposition of the 1JPtPt showed that the solvent also induced rearrangements of the electronic structure, yielding orbitals more localized. The J-coupling mechanism transmission from Fermi contact is affected by changes in the s character of the Pt natural atomic orbitals. Furthermore, it was observed that the Pt—Pt bond polarization caused by the solvent leads to changes in the oxidation state of Pt. (AU)

• FAPESP's process: 18/07308-4 - Effect of solvent on shielding tensor and coupling constant calculations of platinum (iii) dinuclear complexes via ab initio molecular dynamics
• Grantee: Patrick Rodrigues Batista
• Support Opportunities: Scholarships in Brazil - Doctorate