Quantum world chemical bonding

The contributions of Erich Hiickel to the development of molecular orbital theory have already been mentioned in the subsection on Germany (Section 5.4.1) the development of semi-empirical quantum mechanical treatments in organic chemistry by M. J. S. Dewar has been discussed in Section 5.5. In the early development of the application of quantum mechanics to chemistry, Linus Pauling (1901-1994)359 was pre-eminent. He was associated with CalTech for most of his career. His work before World War II generated two influential books the Introduction to Quantum Mechanics (with E. Bright Wilson, 1935)360 and The Nature of the Chemical Bond (1939).361 He favoured the valence-bond treatment and the theory of resonance. 

Most chemists are not even aware that the interpretation of quantum theory may be in dispute. If quantum theory stipulates that atoms grow orbital hair, then so be it. Such things are needed to rationalize chemical bonds after all. But surely, there must be another, logical way out. The known physical world is not unreasonable and if chemistry is to be understood quantum-mechanically, quantum theory better be reasonable. The purpose of what follows is to find that reasonable model, if it exists. 

Ballhausen s latest book [30], Molecular Electronic Structures of Transition Metal Complexes appeared in 1979, 25 years after his first article. It can be seen as his answer to the question What is a molecule - in particular a transition metal complex He starts with his conclusion from a series of articles on the chemical bond [31], Chemistry is one huge manifestation of quantum mechanics . He then introduces the Bom-Oppenheimer approximation as the basis for applying electronic and nuclear coordinates, and lets the picture of a molecule unfold itself with the concepts of electronic states, potential surfaces, transitions, vibronic couplings, etc. The presentation is traditional, but contains many refinings in the discussion of a molecule s ground state as well as its excited states. The world of transition metal complexes is favoured through the choice of examples. 

Putz MV, Duda-Seiman D, Manca S, Duda-Seiman C, Lacrama A-M (2008) Quantum and topological impact on HMG-CoA reductase inhibitors. In Putz MV (ed) Advances in quantum chemical bonding structures, ehap 15. Trans world Research Network, Kerala, pp 355-387... 

In the development of quantum chemistry, physicists and chemists came together from all over the world to arrive at a theory for the chemical bond. This mass amalgamation was promoted by global wars— wars that also represented a philosophic turning point for many Humanism replaced nationalism as the ultimate loyalty. The nation was replaced by the world. 

Mulliken was awarded the Nobel Prize in Chemistry for 1966 "for his fundamental work concerning chemical bonds and the electronic structure of molecules by the molecular orbital method." Barely more than a decade separated this award from the first to reward foundational work in quantum chemistry, which was attributed to Pauling, back in 1954. It had been such a lively decade that by now the two prizes seemed to belong to two worlds many miles apart. As customary, both Nobel award lectures included extensive historical digressions. Both speakers had made these... 

Nascimento M, Barbosa A (2003) Quantum mechanics of many-electrons systems and the theories of chemical bond. In Brandas EJ, Kryachko E (eds) Fundamental world of quantum chemistry, vol 1. Kluwer, Dordrecht, p 371... 

K. Ragavachari and L. A. Curtiss, in Modern Electronic Structure Theory, D. R. Yarkony, Ed., World Scientific Press, Singapore, 1995, pp. 991-1021. Evaluation of Bond Energies to Chemical Accuracy by Quantum Chemical Techniques. 

---