Quantum chemical calculation and experimental measurement of the C-13 chemical shift tensors of vanillin and 3,4-dimethoxybenzaldehyde

The principal values of the C-13 nuclear magnetic resonance chemical shift tensors in vanillin and 3,4-dimethoxybenzaldehyde are reported. Theoretical results of the C-13 chemical shift tensors were obtained by employing the gauge included atomic orbital (GIAO) approach. The geometrical parameters were optimized by using the MNDO method. The observed chemical shifts of these two compounds were determined in powders by using the recently introduced magic angle turning (MAT) experiment. The results presented in this paper clearly demonstrate the importance of using tensor information in the study of molecular structures.