Predicting Ti‐49 <scp>NMR</scp> Chemical Shift With New <scp>NMR</scp> ‐ <scp>DKH</scp> 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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>δ</mml:mi> <mml:mmultiscripts><mml:msub><mml:mi>Ti</mml:mi> <mml:mtext>calc</mml:mtext></mml:msub> <mml:mprescripts></mml:mprescripts> <mml:none></mml:none> <mml:mn>49</mml:mn></mml:mmultiscripts> <mml:mo>=</mml:mo> <mml:mo>-</mml:mo> <mml:mn>1.0027</mml:mn> <mml:mo>×</mml:mo> <mml:msub><mml:mi>σ</mml:mi> <mml:mtext>calc</mml:mtext></mml:msub> <mml:mo>-</mml:mo> <mml:mn>1000.0</mml:mn></mml:mrow> <mml:annotation>$$ \updelta {}^{49}{\mathrm{Ti}}_{\mathrm{calc}}=-1.0027\times {\upsigma}_{\mathrm{calc}}-1000.0 $$</mml:annotation></mml:semantics> </mml:math> ) 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.