83 charge-transfer transition chelation

The intense color of metal chelates is frequently due to charge transfer transitions. This is simply the movement of electrons from the metal ion to the ligand, or vice versa. Such transitions include promotion of electrons from ir levels in the ligand or from a bonding orbitals to the unoccupied orbitals of the metal ion, or promotion of cr-bonded electrons to unoccupied ir orbitals of the ligand. 

Intense charge-transfer transitions observed at the red end of the visible spectrum (14,000-17,000 cm ) for the tungsten (IV) chelates exhibit energy shifts characteristic of metal-to-ligand charge-transfer species and are analogous to those observed for octahedral d ions with unsaturated nitrogen donor atoms e.g., Fe(II) and Ru(II) diimines. 

Vo er A, Kunkeley H (1990) Photochemistry of Transition Metal Complexes Induced by Outer-Sphere Charge Transfer Excitation. 158 1-30 Volkert WA, Jurisson S (1996) Technetium-99m Chelates as Radiopharmaceuticals. 176 123-148... 

Vogler A, Kunkeley H (1990) Photochemistry of Transition Metal Complexes Induced by Outer-Sphere Charge Transfer Excitation. 158 1 - 30 Volkert WAJurisson S (1996) Technetium-99m Chelates as Radiopharmaceuticals. 176 123-148 Vondenhof M, see Mattay J (1991) 159 219-255 VoyerN (1997) The Development of Peptide Nanostructures. 184 1-38 Waldmann H, see Sauerbrei B (1997) 186 65 - 86 Walter C.see FessnerW-D (1997) 184 97-194 Wan P, see Krogh E (1990) 156 93-116... 

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