Complexes_S2008_L3

Complexes_S2008_L3 - Color 1 Color The amount of absorbed...

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1 Color Color 2 Color Color The amount of absorbed The amount of absorbed light versus wavelength is light versus wavelength is an absorption spectrum for an absorption spectrum for a complex. a complex.
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3 Color and Magnetism Color and Magnetism Colors directly opposite each other on the color wheel are complementary. Mixing together two complementary colors of light will give you white light. For example, the absorption spectrum for [Ti(H 2 O) 6 ] 3+ has a maximum absorption at 510 nm (~ green). So, the complex transmits all light except green. Therefore, the complex is purple. Color Wheel: 4 Color and Magnetism Color and Magnetism Magnetism Magnetism Many transition metal complexes are paramagnetic (i.e. they have unpaired electrons). There are some interesting observations. Consider a d 6 metal ion: [Co(NH 3 ) 6 ] 3+ has no unpaired electrons, but [CoF 6 ] 3- has four unpaired electrons per ion. A bonding theory is needed to account for both A bonding theory is needed to account for both color and magnetism in transition metal color and magnetism in transition metal complexes. complexes.
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5 Reminder () 3 2 6 Fe H O + ⎡⎤ ⎣⎦ 26 4 3 Fe Ar s d 4s 3d 3 Fe Ar + Hybridization produces six new orbitals 4p 3d 4s 4d 6 Crystal Crystal -Field Theory Field Theory We assume an octahedral array of negative charges placed around the metal ion (which is positive). The d orbitals lie on the same axes as negative charges. Therefore, there is a large, unfavorable interaction between ligand (-) and these orbitals. These orbitals form the degenerate high energy pair of energy levels. The d xy , d yz , and d xz orbitals bisect the negative charges so there is a smaller repulsion between ligand and metal for these orbitals. These orbitals form the degenerate low energy set of energy levels.
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7 Crystal Crystal -Field Theory Field Theory There are some ligand- d - electron repulsions which occur since the metal has partially filled d -orbitals. In an octahedral field, the degeneracy of the five d orbital's is lifted. The complex metal ion has a lower energy than the separated metal and ligands.
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Complexes_S2008_L3 - Color 1 Color The amount of absorbed...

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