Organosilyl/-germyl Polyoxotungstate Hybrids for Covalent Grafting onto Silicon Surfaces: Towards Molecular Memories

Organosilyl/-germyl polyoxotungstate hybrids [PW9O34(tBuSiO)(3)Ge(CH2)(2)CO2H](3-) (1a), [PW9O34(tBuSiO)(3)Ge(CH2)(2)CONHCH2C CH](3-) (2a), [PW11O39Ge(CH2)(2)CO2H](4-) (3a), and [PW11O39Ge(CH2)(2)CONHCH2C CH](4-) (4a) have been prepared as tetrabutylammonium salts and characterized in solution by multinuclear NMR spectroscopy. The crystal structure of (NBu4)(3)1a center dot H2O has been determined and the electrochemical behavior of la and 2a has been investigated by cyclic voltammetry. Covalent grafting of 2a onto an n-type silicon wafer has been achieved and the electrochemical behavior of the grafted clusters has been investigated. This represents the first example of covalent grafting of Keggin-type clusters onto a Si surface and a step towards the realization of POM-based multilevel memory devices.