Nuclear magnetic resonance (NMR) is a powerful tool for studying the absorption of radio-frequency radiation by atomic nuclei. In a strong magnetic field, the nuclei and electronic energy of certain elements are magnetic, so the nucleus will undergo energy level splitting. When absorbing external electromagnetic radiation, it will split into two or more quantized energy levels. When electromagnetic radiation of appropriate frequency is absorbed, a transition can occur between the generated magnetically induced energy levels, resulting in a NMR phenomenon. In a magnetic field, a nuclear magnetic molecule or nucleus absorbs the energy of the transition from a low energy state to a high energy state will produce a resonance spectrum, which can be used to determine the number, type and relative position of certain atoms in the molecule. According to the object to be measured, NMR spectrum can be classified into the following: 1H-NMR spectrum, 13C-NMR spectrum, fluorine spectrum, phosphorus spectrum, nitrogen spectrum, etc. 1H-NMR and 13C-NMR spectrum are commonly applied in the study of material structure and performance since organic compounds and polymer materials are mainly composed of hydrocarbons.
Figure 1. DFT analysis of the 125Te NMR Knight shifts in Bi2Te3 nanoplatelets. (Papawassiliou, W.; et al. 2020)
Identify groups according to chemical shift, determine the way groups are connected by the number of coupling splitting peaks and coupling constant, determine the proton ratio of each group according to the integral area of the peak of each H atom.
NMR technology has been successfully used to detect defects or damages in materials. Scientists use it to study the pore size distribution in extruded or foamed materials, adhesives, and porous materials. NMR technology can be applied to improve processing conditions and product quality.
NMR technology can be used to measure the relaxation time of polymer blends, determine their compatibility, and investigate the structural stability and performance of materials.
Study polymerization reaction mechanism, polymer sequence structure, qualitative identification of unknown polymers, mechanical and physical properties analysis, etc.
Optimize the molecular structure to get the most stable conformation.
Use a larger basis set to optimize molecule which is then used as the initial structure for NMR calculation. The magnetic shielding value of the sample molecule can be obtained in this step.
Subtract the magnetic shielding values of the same atomic nuclei in the sample molecule from the magnetic shielding values of H and C atom in the reference, the chemical shift value corresponding to the experimentally measured value can be obtained.
At Alfa Chemistry, we mainly apply machine learning (ML) and density functional theory (DFT) method for the NMR spectrum prediction, assisting in the follow-up chemical characterization and identification. Our fast and high-quality services include the following:
We have developed deep neural networks for predicting single-atom properties of molecules including NMR shifts. Our teams can predict multiple spectroscopic parameters for structure elucidation such as indirect dipolar coupling (J-coupling) coefficients and nuclear Overhauser-effect (NOE) couplings.
At Alfa Chemistry, 1H NMR chemical shifts and coupling constants for several aromatic and aliphatic organic molecules have been calculated with DFT methods. Our experts have also analyzed the performance of several functionals and basis sets. Moreover, various contributions to spin-spin coupling (Fermi-contact, diamagnetic and paramagnetic spin-orbit) have been evaluated.
NMR spectrum prediction provides complete prediction of the NMR spectrum of various molecules for structural identification. Our NMR spectrum prediction services remarkably reduce the cost, promote further experiments, and enhance the understanding of chemical process for customers worldwide. Our personalized and all-around services will satisfy your innovative study demands. If you are interested in our services, please don't hesitate to contact us. We are glad to cooperate with you and witness your success!