Theoretical study on metal <scp>NMR</scp> chemical shifts: Germanium compounds

Nakatsuji, Hiroshi; Nakao, Takayuki

doi:10.1002/qua.560490316

Cited by 11 publications

(1 citation statement)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have investigated the mechanism of the chemical shifts for a variety of metal complexes and found that the primary mechanism of the chemical shift is an intrinsic property of the central resonant metal atom itself and therefore can be understood from the position of the element on the periodic table. [132][133][134][135][136][137][138][139][140][141][142] However, this is not the case when we examine the chemical shift induced by the halogen ligands. We have two different dependences: normal halogen dependence and inverse halogen dependence.…”

Section: Relativistic Quantum Chemistry and The Electronic Theory Of mentioning

confidence: 99%

Deepening and Extending the Quantum Principles in Chemistry

Nakatsuji

2005

Bulletin of the Chemical Society of Japan

View full text Add to dashboard Cite

A brief summary of the author's research projects for deepening and extending the quantum principles in chemistry is given. First, the structure of the exact wave function that is the solution of the Schrödinger equation was clarified and a method of calculating it starting from an approximate wave function is given. The singularity problem intrinsic to atoms and molecules was overcome, and a general method of solving the Schrödinger equation in an analytical form has been established. Quantum chemistry of excited states and ionized states is essential since it is difficult with experiments alone to explore this field due to the short lives of these species. The SAC-CI theory developed in the author's groups offers a powerful method for investigating the chemistry of excited and ionized states. The energy gradient method incorporated into this program is particularly useful for studying geometries and reactions involving these states. The catalysis on a metal surface is a magic process that must be clarified with the help of quantum theory. The author studied it using his dipped adcluster model (DAM) that includes the effects of the free electrons of the bulk metal. The epoxidation reactions of ethylene and propylene were studied with this method. The NMR chemical shifts include much information about the valence electrons of molecular systems. The author clarified that the major electronic mechanisms of the chemical shifts could be attributed to the intrinsic atomic properties that are related to the position of the element in the periodic table.For the chemical shifts induced by heavy ligands, the relativistic effect is sometimes dominant. The spin-orbit effect is most important for light resonant nuclei. For heavier resonant nuclei, other spin-free relativistic effects and the electron correlation effects are also important and they strongly couple with each other, implying an existence of something ''unexpected'' in the chemistry of heavy elements. Finally, the strategy of the author's study in quantum chemistry is shortly described.

show abstract

Section: Relativistic Quantum Chemistry and The Electronic Theory Of mentioning

confidence: 99%

Deepening and Extending the Quantum Principles in Chemistry

Nakatsuji

2005

Bulletin of the Chemical Society of Japan

View full text Add to dashboard Cite

show abstract

The calculation of NMR shielding tensors based on density functional theory and the frozen-core approximation

Schreckenbach

Ziegler

1996

Int. J. Quantum Chem.

160

136

View full text Add to dashboard Cite

rnThe application of the frozen-core approximation to the calculation of the shielding tensor of nuclear magnetic resonance (NMR) spectroscopy is discussed and an implementation is presented. A complete formulation of the shielding calculation within the frozen-core approximation is given, both in general t e r m and for the special case of density functional theory (DFT) and "gauge including atomic orbitals" (GIAOs). The practical implementation is validated by a detailed discussion of the consequences of the approximation. The general conclusion is drawn that the frozen-core approximation is a useful tool for shielding calculations-if the valence space is increased to contain at least the ns, np, ( n -l)p, ( n -l ) d (fourth period and higher) shells, where n is the number of the given period in the periodic table of elements. The new method is applied to nSe shieldings and chemical shifts for a small number of compounds. The agreement between theory and experiment is good for relative shifts, whereas calculated absolute shieldings are generally too small by about 300-400 ppm. This difference is attributed to the relativistic contraction of the core density at the selenium atom that had been explicitly incorporated into the experimental absolute shielding scale. 0 1996 John Wiley & Sons, Inc.of chemistry and beyond. The range of nuclei that can be studied by NMR is steadily increasing. Thus, the area of multinuclear NMR, i.e., the study of nuclei other than--say-',*H, I3C, l4,I5N, I9F, 31 P, or 33S, is rapidly gaining importance [ll.The theoretical prediction of shielding tensors has a long and successful history. These calculations are carefully reviewed annually [21. A good

show abstract