Solvent effect on the¹⁹⁵Pt NMR properties in pyridonate-bridged Pt^IIIdinuclear complex derivatives investigated byab initiomolecular dynamics and localized orbital analysis

Anab initiomolecular dynamics investigation of the solvent effect (water) on the structural parameters,¹⁹⁵Pt NMR spin-spin coupling constants (SSCCs) and chemical shifts of a series of pyridonate-bridged Pt^IIIdinuclear complexes is performed using Kohn-Sham (KS) Car-Parrinello molecular dynamics (CPMD) and relativistic hybrid KS NMR calculations. The indirect solvent effect (viastructural changes) has a dramatic effect on the¹J_PtPtSSCCs. The complexes exhibit a strongtransinfluence in solution, where the Pt-Pt bond lengthens with increasing axial ligand σ-donor strength. In the diaqua complex, where the solvent effect is more pronounced, the SSCCs averaged for CPMD configurations with explicit plus implicit solvation agree much better with the experimental data, while the calculations for static geometry and CPMD unsolvated configurations show large deviations with respect to experiment. The combination of CPMD with hybrid KS NMR calculations provides a much more realistic computational model that reproduces the large magnitudes of¹J_PtPtand¹⁹⁵Pt chemical shifts. An analysis of¹J_PtPtin terms of localized and canonical orbitals shows that the SSCCs are driven by changes in the s-character of the natural atomic orbitals of Pt atoms, which affect the 'Fermi contact' mechanism.