Lecture 17 - Crystal Field Theory Chem 172 Advanced...

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1 Chem 172 Advanced Inorganic Chemistry Lecture 16/May 7 th Coordination Bond Theory Crystal Field Theory ± Crystal Field Theory was originally developed to describe the electronic structure of metal ions in a crystal, where they electrostatic interact with surrounding anions of certain symmetry defined by the crystal structure. ± Adapted to coordination complexes, it can be used to understand, interpret and predict the magnetic, optical (color) and thermodynamic properties of coordination complexes. ± The crystal field model concentrates on the splitting of the d orbitals of the transition metal atom into groups as a result of electrostatic interactions between the ligands and the electrons in the unhybridized orbitals of the transition metal atom. d-Orbital Energy Split in an Octahedral Field ± In octahedral field, d orbital split into a lower energy triply degenerate set (t 2g ) and a higher energy doubly degenerate set (e g ). The magnitude of splitting parameter ( ' o ) vs. pairing energy ( P ) can fundamentally affect how electrons are filled in the d orbitals, and determining the spectroscopic, magnetic, and thermodynamic stability of the complexes. Ligand Field Theory (LFT) ± Crystal-field theory provides a simple conceptual model and can be used to interpret spectra and thermochemical data by appealing to empirical values of ' .On closer inspection, however, the CFT is defective because it treats ligands as point charges or dipoles and does not take into account the overlap of ligand and metal orbitals ± Ligand Field Theory uses Molecular Orbital Theory to derive the ordering of orbitals within metal complexes.
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Lecture 17 - Crystal Field Theory Chem 172 Advanced...

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