Conformationally Modulated Intramolecular Electron Transfer Process in a Diaza[2,2]ferrocenophane

A novel conformationally modulated Intramolecular Electron Transfer (IET) phenomenon has been observed due to the cyclic structure of the diaza[2.2]ferrocenophane 3. The corresponding mixed-valence compound of 3, prepared by electrochemical or chemical partial oxidation, interestingly shows the appearance of two absorption bands in the near infrared (NIR) spectral region. These bands are attributable to two intervalence charge-transfer transitions associated to two atropoisomers exhibiting different energy for the IET process. A solvent and temperature control over the atropoisomeric equilibrium have also been observed. The experimental data and conclusions about both the conformational and the electronic properties of compound 3 are also supported by density functional theory calculations.