Crystal field theory magnetic properties

The effects of the bonding electrons upon the d electrons is addressed within the subjects we call crystal-field theory (CFT) or ligand-field theory (LFT). They are concerned with the J-electron properties that we observe in spectral and magnetic measurements. This subject will keep us busy for some while. We shall return to the effects of the d electrons on bonding much later, in Chapter 7. 

The analogy between the two theories is only formal. Crystal field theory is a purely electrostatic approach that does not take into consideration the formation of MOs and the nature of the bond. According to crystal field theory, optical and magnetic properties are ascribed to crystal field splitting between two AOs, whereas in ligand field theory energy splitting occurs between AOs, and... 

Crystal Field Theory magnetic and spectra] properties of complexes. In addition, it provided a basis for... 

Chapter 11 Coordination Chemistry Bonding, Spectra, and Magnetism 387 Bonding in Coordination Compounds 391 Valence Bond Theory 391 Crystal Field Theory 394 Molecular Orbital Theory 413 Electronic Spectra of Complexes 433 Magnetic Properties of Complexes 459... 

Although the physical basis of the crystal field model is seen to be unsound, the fact remains that, in summarizing the importance of the symmetry of the ligand environment, it qualitatively reproduces many of the features of the magnetic and spectral properties of transition metal complexes. This early qualitative success established its nomenclature in the fields of these properties. While we shall have little more to say about crystal field theory as such, much of the rest of this article will be couched in the language of the crystal field model, and for that reason some little trouble has been taken to outline its development. 

Crystal field theory accounts for the magnetic properties of complexes as well as for their color. It explains, for example, why complexes with weak-field ligands,... 

Considerable interest centres on the Mantle constituting, as it does, more than half of the Earth by volume and by weight. Attention has been focussed on several problems, including the chemical composition, mineralogy, phase transitions and element partitioning in the Mantle, and the geophysical properties of seismicity, heat transfer by radiation, electrical conductivity and magnetism in the Earth. Many of these properties of the Earth s interior are influenced by the electronic structures of transition metal ions in Mantle minerals at elevated temperatures and pressures. Such effects are amenable to interpretation by crystal field theory based on optical spectral data for minerals measured at elevated temperatures and pressures. 

The cationic forms of zeolites are experimentally investigated rather well by various spectroscopic techniques, including IR, ESR, NMR, and UV VIS spectroscopy. Structural interpretation of the spectroscopic data requires quantum-chemical computations of the optical and magnetic properties of 3d-element ions in different environments. For this purpose, Mikheikin et al. (98, 99) have applied a simple crystal-field theory to discuss the optical and magnetic properties of ions with a dn shell (n = 1,. 9) in the crystal field of low symmetry. The results could be used to discuss optical and ESR spectra of faujasites containing Cu2+, Co2+, Cr3+, Fe3+, Ni2+, and Mn2 + ions and their complexes with various molecules (H20, NH3, CH3OH, C2FI5OH, etc.). 

Crystal Field Theory Optical and Magnetic Properties... 

Experimental measurements of the optical absorption spectra and magnetic properties of transition-metal complexes provide a critical test of the validity of crystal field theory. The theory makes specific predictions about the strengths of crystal fields produced by different ligands. Charged ligands such as the halides... 

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