)1Faculty of Physics, Photonics Department, St. Petersburg State University, 198904 St. Petersburg, Russia.
2Advanced Research Center, Sankt-Petersburg State Technical University, 194021 St. Petersburg, Russia.
)Transition metal pi-complexes such as ferrocenes and bis-arenechromium are very promising molecular structures to design perspective new materials for nanoscale molecular electronics. They can serve as a source of electrons capable take part in charge transfer between two or more remote metal centers. The first ionization potentials of sandwich compounds are very low, as a rule, and can be easily controlled by relevant substituents. Our interest lies in the field of effective molecular wires study. The [n]-cumulenes are the best choice due to very simple and most unsaturated form with linear rigid structure. They can provide a strong pi-pi conjugation between electroactive terminal ferrocenyl substituents.
We present here the results of investigation of alpha, omega - diferrocenyl cumulenes by quantum-chemical calculations at the DFT (B3LYP/6-31G) level with full geometry optimization both neutral and charged forms. The main goal of this contribution is the full description of structural (X-ray), spectroscopic (IR, UV-vis) and electrochemical (CV) data [1]. The main efforts went into solvated molecular wires treatment with a self-consistent reaction field method in order to evaluate redox potentials as function of cumulene length more accurately. The calculated values described the CV data with reasonable accuracy.
Very unusual effects can be expected from the theoretical results on conformations of dications and dianions of diferrocenyl [5]-cumulene. We have found out that conformations of these species changed drastically. The end group of ions is turned exactly on 90 degrees in comparison to neutral molecule. The reason of this effect lies in HOMO properties of diferrocenyl [5]-cumulene. We suppose that these findings open way to constructing molecular electronanomechanical elementary units with electrically controlled rotational displacement of end groups.
