NMR chemical shift computation structural applications

Buhl, M. 1998, NMR Chemical Shift Computation Structural Applications , in Encyclopedia of Computational Chemistry, Schleyer, P. v. R. (Editor-in-Chief), Wiley, Chichester. 

Basis Sets Correlation Consistent Sets Carbocation Force Fields Coupled-cluster Theory Enthalpies of Hydrogenation G2 Theory Heats of Formation Hyperconjugation NMR Chemical Shift Computation Structural Applications NMR Data Correlation with Chemical Structure Proton Affinities. 

The definitive method for determining static structures is X-ray diffraction. Indeed, the 1976 Nobel Prize in Chemistry was awarded to Professor William N. Lipscomb for his work in determining structures of the boron hydrides by diffraction methods. However, it must be remembered that packing forces and solvation effects may change the preferred structure between solid state and solution. Another technique, which combines theory and experiment, has established a reliability on a par with X-ray diffraction for confirming structures. It is called the ab /n/n o/IGLO/NMR method (see NMR Chemical Shift Computation Structural Applications for an extensive discussion of calculated NMR chemical shifts) and combines calculated chemical shifts for a number of possible structures with the experimentally measured chemical shifts in solution. 

Density Functional Applications MNDO NMR Chemical Shift Computation Structural Applications Reaction Path Following Topological Methods in Chemical Structure and Bonding. 

Conformational Sampling Distance Geometry Theory, Algorithms, and Chemical Applications Macromolecular Structure Calculation and Refinement by Simulated Annealing Methods and Applications NMR Chemical Shift Computation Structural Applications NMR Refinement. 

Another important second-order property, which is considerably improved by MP correlation effects is the NMR chemical shift (see NMR Chemical Shift Computation Ab Initio and NMR Chemical Shift Computation Structural Applications). Calculations by Gauss have shown that for C shifts accurate values are already obtained at the GIAO-MP2 level. Further improvements are obtained by GIAO-MP3 and GIAO-MP4(SDQ) calculations. In the case of molecules with multiple bonds such as N2, the inclusion of T effects... 

Basis Sets Correlation Consistent Sets Complete Active Space Self-consistent Field (CASSCF) Second-order Perturbation Theory (CASPT2) Configuration Interaction Coupled-cluster Theory Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field G2 Theory Geometry Optimization 1 Gradient Theory Inter-molecular Interactions by Perturbation Theory Molecular Magnetic Properties NMR Chemical Shift Computation Ab Initio NMR Chemical Shift Computation Structural Applications Self-consistent Reaction Field Methods Spin Contamination. 

After the introduction of IGLO, molecules of chemical interest became accessible to ab initio calculations. Early applications included the ab initio derivation of an increment system for hydrocarbons, a definite confirmation of the non-classical structure of the 2-norbomylcation, the assignment of the shift tensors of cyclopropane, bicyclobutane, and [1.1.1]-propellane, and the prediction of the F shift in SF2 prior to its measurement. These applications have been reviewed (see NMR Chemical Shift Computation Structural Applications). 

Since about 1990, powerful post-Hartree-Fock approaches for the inclusion of electron correlation in chemical shift calculations have been developed and applied in main group chemistry (see NMR Chemical Shift Computation Ab Initio and NMR Chemical Shift Computation Structural Applications). Unfortunately, these correlated methods are computationally too demanding at present to be applied to transition metal complexes and clusters of chemically relevant size. In particular, the least expensive post-CHF method available, the MP2-GIAO approach, is expected to fail for systems with significant nondynamical correlation effects. 

Chemometrics Multivariate View on Chemical Problems Combinatorial Chemistry Factual Information Databases Fuzzy Methods in Chemistry Infrared Data Correlations with Chemical Structure Infrared Spectra Interpretation by the Characteristic Frequency Approach Inorganic Chemistry Databases Inorganic Compound Representation NMR Chemical Shift Computation Ab Initio NMR Chemical Shift Computation Structural Applications NMR Data Correlation with Chemical Structure Online Databases in Chemistry Spectroscopy Computational Methods Standard Exchange Formats for Spectral Data Structure and Substructure Searching Structure Determination by Computer-based Spectrum Interpretation Structure Generators Synthesis Design. 

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