关键词:
Magnetic properties
Wave function
Quantum mechanics
Chemical calculations
Ligands
摘要:
Ligand paramagnetic NMR (pNMR) chemical shifts of the 5f(1) complexes UO2(CO3)(3)(5-) and NpO2(CO3)(3)(4-), and of the 5f(2) complexes PuO2(CO3)(3)(4-) and (C5H5)(3)UCH3 are investigated by wave function theory calculations, using a recently developed sum-over-states approach within complete active space and restricted active space paradigm including spin-orbit (SO) coupling [J. Phys. Chem. Lett. 2015, 20, 2183-2188]. The experimental C-13 pNMR shifts of the actinyl triscarbonate complexes are well reproduced by the calculations. The results are rationalized by visualizing natural spin orbitals (NSOs) and spin-magnetizations generated from the SO wave functions, in comparison with scalar relativistic spin densities. The analysis reveals a complex balance between spin-polarization, spin and orbital magnetization delocalization, and spin-compensation effects due to SO coupling. This balance creates the magnetization due to the electron paramagnetism around the nucleus of interest, and therefore the pNMR effects. The calculated proton pNMR shifts of the (C5H5)(3)UCH3 complex are also in good agreement with experimental data. Because of the nonmagnetic ground state of (C5H5)(3)UCH3, the H-1 pNMR shifts arise mainly from the magnetic coupling contributions between the ground state and low-energy excited states belonging to the Sf manifold, along with the thermal population of degenerate excited states at ambient temperatures.