Chapter 3 Notes: Colored complexes Chapter 13.2: d orbitals have the same energy in an isolated atom, but split into two sub-levels in a complex ion. The electric field of ligands cause the d orbitals in complex ions to split so that the energy of an electron transition between them corresponds to a photon of visible light. Chapter 3 Notes: Colored complexes

Important terms for this section Colored complexes Nuclear charge Charge density Oxidation state

The color absorbed means the complementary color is reflected (so you will see it) If copper chloride is cyan (blue-green), then red-orange is being absorbed

Why do TM absorb light? In a TM complex, d-sublevel splits when an electric field (or light) is applied One of the 3d electrons is excited to a higher sub-level Note: Not same as e- emitting photon when return to ground state

Color depends on… The difference in energy between the split sublevels The nuclear charge Identity of central metal ion Charge and density of ligand Geometry of complex ion Oxidation number of central metal ion (number of d electrons)

Nuclear charge and ID of metal Higher nuclear charge More strongly interacting with its ligands Therefore, absorbs light with higher energy Ex: [Mn(H2O)6]2+ vs [Fe(H2O)6]3+ Mn = lower ENC  absorbs green  show pink Fe = higher ENC  absorbs blue  show orange

Charge density of the ligand Charge density: density of charge around the ion Greater the charge density of the ligand Greater the split of the d orbitals Absorbs higher energy light Spectrochemical series of ligands: separates ligands by energy separation of d orbitals Spectrochemical series is in Section 15 of data booklet

Number d electrons and oxidation state of central metal ion Oxidation state of metal depends on no. of d e- More e- means more repulsion of ligand This means less interaction of metal with ligand If oxidation number is higher = ligand repulsed by d e- and greater splitting of d orbitals Vanadium oxidation state ions 