Colors origin, transition metal coordination

ORIGIN OF COLOR IN TRANSITION METAL COORDINATION COMPLEXES4... 

Color is a spectacular property of coordination complexes. For example, the hexaaqua cations of 3 transition metals display colors ranging from orange through violet (see photo at right). The origin of these colors lies in the d orbital energy differences and can be understood using crystal field theory. 

The weak electron transitions responsible for the color of coordination complexes are correlated with the t2g to eg transition of energy A. The origin of the strong transitions responsible for the deep colors of some complexes of metals in high oxidation states, like the permanganate and the chromate ions, has a different explanation not covered here. 

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