Extending the Molecular Tailoring Approach for Reliable and Efficient Nuclear Magnetic Resonance Spectral...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Calculating nuclear magnetic resonance (NMR) spectral parameters for large molecules using high-level theory and large basis sets is computationally intensive.
• Existing methods often struggle with scalability, requiring significant computational resources or failing for very large systems.

Purpose of the Study:

• To propose an efficient and accurate fragment-based protocol for evaluating NMR parameters in large molecular systems.
• To enable the study of NMR features in complex molecules that are intractable with standard computational approaches.

Main Methods:

• A fragment-based protocol was developed to approximate isotropic shielding tensors and spin-spin coupling constants.
• The molecular tailoring approach (MTA) was employed in conjunction with a grafting procedure for calculations at the DFT/MP2 level.
• The methodology was validated against full conventional calculations and experimental results for selected test cases.

Main Results:

• The fragment-based protocol combined with MTA demonstrated excellent agreement with full conventional calculations for medium-sized molecules.
• The accuracy of the proposed method was confirmed through comparison with experimental NMR data.
• Significant acceleration in computation time was achieved through independent and parallel fragment calculations.

Conclusions:

• The proposed fragment-based protocol offers an affordable and practical solution for computing NMR parameters of large molecular systems.
• This methodology is particularly valuable for tackling systems where standard ab initio codes are computationally prohibitive.
• The approach facilitates the examination of NMR features in large molecules using readily available hardware.