pigments_lect3(1)

pigments_lect3(1) - 1 Color and Bonding in Color and...

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Unformatted text preview: 1 Color and Bonding in Color and Bonding in Transition Metal Complexes Transition Metal Complexes Chemistry 123 Chemistry 123 Dr. Patrick Woodward Dr. Patrick Woodward Supplemental Lecture 3 Supplemental Lecture 3 Intra Intra-atomic (localized) excitations atomic (localized) excitations Transition metal ions, complex ions & compounds (d-orbitals) Lanthanide ions and compounds (f-orbitals) [Ni(NH 3 ) 6 ] 2+ NiSO 4 Cu 3 (CO 3 ) 2 (OH) 2 Malachite CuSO 4 In these complexes the color comes from absorption of light that leads to excition of an electron from an occupied d-orbital to an empty or -filled d-orbital. The energy separation between d-orbitals depends upon the interaction between the d- orbitals and the ligands. There are two ways to rationalize the energy separation Crystal Field Theory & Ligand Field Theory. 2 d z 2 & d & d x 2-y 2 orbitals ( orbitals ( e g ) Point directly at the ligands Stronger (repulsive) interaction with the ligands Crystal Field Splitting (Octahedron) Crystal Field Splitting (Octahedron) d z 2 d x 2-y 2 d xy xy d yz yz d xz xz Electrons in d-orbitals are repelled from the electrons in the ligands, based on electrostatic interactions. This causes two of the d-orbitals (dz 2 & dx 2-y 2 ) to be at higher energy than the other three (dxy, dyz, dxz) Energy d xy xy , , d yz yz & & d xz xz orbitals (t orbitals (t 2g 2g ) Point between the ligands Weaker (repulsive) interaction with the ligands d z 2 & d & d x 2-y 2 orbitals ( orbitals ( e g ) Point directly at the ligands Sigma antibonding interaction with the ligands Ligand Ligand Field Splitting (Octahedron) Field Splitting (Octahedron) d z 2 * d x 2-y 2 * d xy xy * d yz yz * d xz xz * d xy xy , , d yz yz & & d xz xz orbitals (t...
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This note was uploaded on 06/03/2011 for the course CHM 123 taught by Professor Woodward during the Spring '08 term at Ohio State.

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pigments_lect3(1) - 1 Color and Bonding in Color and...

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