question_answer 91)

    What is the relationship between observed colour of the complex and the wavelength of light absorbed by the complex?

Answer:

                    When white light falls on the complex, some part of it is absorbed. Higher the crystal field splitting energy lower will be the wavelength absorbed by the complex. The observed colour of complex is the colour generated from the wavelength left over. e.g., if green light is absorbed, the complex appears red. In some of crystal field theory, suppose there is an octahedral complex with empty  level and unpaired electrons in the  level in ground level. If the unpaired electron absorbs light corresponding is blue-green region, it will excite to  level and the complex will appear violet in colour In absence of ligand, crystal field splitting does not occur and the substance is colourless. e.g., anhydrous  is while, but  is blue in colour.           .