Exercice III. Copper metalloproteins

In nature, electron transfer is provided by metalloproteins to perform the oxidationreduction processes necessary for the functioning of organisms. Umecyanin is one example of such metalloproteins. The site involved in the electron transfer reaction is a copper complex $($C$).$ In the following, we will examine the physicochemical implications during the electron transfer reaction.

i$)$ Make an electron counting for this complex oxidation state, $d^n$ configuration, total number of electrons$)$

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ii$)$ Complex C may have a square planar geometry or tetrahedral geometry. Give the splitting of the orbitals of the block for both symmetries using Angular Overlap Model.

iii$)$ Give the spin state of $C$ for each geometry, knowing all ligands have a weak field.

iv$)$ Calculate the energies for the two possible geometries for $C$ in terms of $e_{}$ using angular overlap model. You will consider that all ligands have the same $e_{}$ value.

v$)$ On an energy diagram place the relative position of the two possible geometries of $C.$ Which geometry is more stable?

vi$)$ Complex C acts as an electron relay by first accepting an electron to give complex D with the same ligands in the coordination sphere. Complex $D$ then gives an electron to another electron relay $R,$ to go back to the complex $C.$ Write the reaction going from $C$ to $D$ taking into account the possible charge of the complexes.

vii$)$ Make the electronic count of complex $D($oxidation state, $d^n$ configuration, total number of electrons$)$ for both geometries.

viii$)$Give the spin state of complex $D$ for the square planar and the tetrahedral geometries.

ix$)$ Calculate the energies for the two possible geometries for $D$ in terms of $e_{}.$ What can you conclude on the geometry preference of $D?$

$x)$ Taking into account the minimum repulsion, what geometry $D$ will adopt?

Place on the energy diagram in iv$)$ the energy of $D.$ What is the energy needed for the reduction process of $C($considering both square planar and tetrahedral geometries$)$ to D$.$