Assessment of the Accuracy of Theoretical Methods for Calculating 27Al Nuclear Magnetic Resonance Shielding Tensors of Aquated Aluminum Species

Abstract

Assessment of the accuracy of methods including 29 DFT methods and 2 ab initio wave function theory (WFT) methods for predicting (27)Al nuclear magnetic resonance shielding tensors of aquated Al(III) species was carried out. Among all of the tested methods, HF and MP2 methods give the best performance for the calculations of chemical shifts. Among all of the DFT methods with GIAO calculations, O3LYP and MPWKCIS1K are the most accurate models for calculations of chemical shifts, followed in order by BHandHLYP, B98, B97-1, mPW1PW91, PBE1PBE, and MPW1KCIS. Among all of the DFT methods with CSGT calculations, VSXC is the best method for the prediction of chemical shifts, followed in order by TPSSh, B97-2, O3LYP, TPSS, TPSS1KCIS, MPWKCIS1K, BHandHLYP, B97-1, and B98. The popular B3LYP method overestimates largely the chemical shifts with both GIAO and CSGT methods. The calculated results indicate that the predictions of (27)Al chemical shifts on the base of the model that includes both explicit solvent effect and bulk solvent effect are most accurate for aquated Al(III) species.