Predicting Ti-49 NMR Chemical Shift With New NMR-DKH Basis Set

In the present study, a computational protocol for predicting the Ti-49 NMR chemical shift (δ⁴⁹Ti) was constructed with our NMR-DKH basis sets for all atoms, including titanium (Ti), which was developed in this work. Thus, computational protocols were proposed considering 55 different DFT functionals using nonrelativistic Hamiltonian. Besides, four-components (4c) calculations employing the relativistic modified Dirac-Kohn-Sham Hamiltonian at GIAO-4c-BLYP/dyall.VDZ level was also considered. In the best protocol, the structures of the 41 Ti(IV) complexes studied, which cover a wide range of δ⁴⁹Ti ranging from -1389 to +1325 ppm, were optimized at the BLYP/def2-SVP/IEF-PCM (UFF) level and the δ⁴⁹Ti was calculated at the GIAO-OLYP/NMR-DKH/IEF-PCM (UFF) level, both employing a nonrelativistic Hamiltonian. In this protocol, a mean absolute deviation (MAD) of only 48 ppm and a coefficient of determination (R²) of 0.9888 were found, which represents an excellent agreement, and with lower computational cost, with the MAD of 62 ppm and R² of 0.9860 obtained with the relativistic full 4c Hamiltonian at GIAO-4c-BLYP/dyall.VDZ, indicating that the proposed protocol with the NMR-DKH basis set is an excellent alternative for the study of Ti-49 NMR. Additionally, a predictive model based on linear regression ( $\delta {}^{49}{\mathrm{Ti}}_{\text{calc}}=-1.0027\times {\sigma }_{\text{calc}}-1000.0$ ) was developed, adjusted from 41 complexes and validated in an external set of nine Ti(IV) complexes, presenting a MAD of 48 ppm and confirming the robustness and extrapolation capacity of the proposed protocol.