Question

For CO2+

1.Assuming that it has an octahedral geometric configuration, draw an orbital energy diagram and place the valence electrons in the diagram for its ground state.

2. For the same complex, draw an orbital energy diagram and place the valence electrons in the diagram that would indicate that it is in an excited state.

3. Using the two energy diagrams and the color you have chosen (as the color absorbed), describe the process by which transition metal complexes display color. Make sure you include delta Oct, the color that ould be observed and any other relavant information. The color chosen was RED

Answer 1

The d-orbitals of a free transition metal atom or ion are degenerate (all have the same energy.) However, when transition metals form coordination complexes, the d-orbitals of the metal interact with the electron cloud of the ligands in such a manner that the d-orbitals become non-degenerate (not all having the same energy.) The way in which the orbitals are split into different energy levels is dependent on the geometry of the complex. Crystal field theory can be used to predict the energies of the different d-orbitals, and how the d-electrons of a transition metal are distributed among them. When the d-level is not completely filled, it is possible to promote and electron from a lower energy d-orbital to a higher energy d-orbital by absorption of a photon of electromagnetic radiation having an appropriate energy. Electromagnetic radiations in the visible region of the spectrum often possess the appropriate energy for such transitions. The sensors in our eyes detect only those wavelengths in the visible portion of the electromagnetic spectrum. Although visible light appears "white", it is made up of a series of colors. White light consists of three primary colors (red, yellow and blue). These primary colors can be mixed to make three secondary colors (orange, green and violet).

An "artist's" color wheel is a useful way show to these relationships. If you add the colors on opposite sides of the wheel together, white light is obtained. We only detect colors when one or more of the wavelengths in the visible spectrum have been absorbed, and thus removed, by interaction with some chemical species. When the wavelengths of one or more colors is absorbed, it is the colors on the opposite side of the color wheel that are transmitted. If red, yellow, orange, blue and violet are absorbed only one color is transmitted ...GREEN.

When light passes through a solution containing transition metal complexes, we see those wavelengths of light that are transmitted. The solutions of most octahedral Co (II) complexes are pinkish red. The visible spectrum for an aqueous solution of Co (II), [Co(H₂O₆]²⁺, shows that the absorption band spans the redportion of the spectrum and green colour is transmitted. The absorption band corresponds to the energy required to excite an electron from the t_2g level to the e_g level.