Question

Coordination compounds exhibit color which is attributed to the?

Answer 1

Coordination compounds:

• “The transition metals form a large number of complex compounds in which the metal atoms are bound to a number of anions or neutral molecules by sharing electrons. In modern terminology, such compounds are called coordination compounds.”

Color of coordination compounds:

• The color in coordination compound exhibited due to the d-d transition.
• It can be attributed to the crystal field theory.
• For example, the complex $[\mathrm{Ti}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6{]}^{3+}$ which is violet in color.
• This is an octahedral complex where the single electron (${\mathrm{Ti}}^{3+}$ is a $3{\mathrm{d}}^1$ system) in the metal d orbital is in the${\mathrm{t}}_2\mathrm{g}$ level in the ground state of the complex.
• The next higher state available for the electron is the empty $\mathrm{eg}$ level. If light corresponding to the energy of blue-green region is absorbed by the complex, it would excite the electron from ${\mathrm{t}}_2\mathrm{g}$ level to the $\mathrm{eg}$ level.