Future of electronics will require using single molecule as the active component in electric circuitry. In that vein our group and others have developed single molecule switches1,2, single molecular diodes3, single molecular resistors and transistors4. All these previous studies utilized alkynes, amines, thiols as anchoring groups to metals (mostly on gold (Au)). Despite the popularity of the S-Au linkers, they are mechanically unstable and their contact resistance is variable which complicates device fabrication. To realize molecular electronics devices a change towards more robust contacts is needed. In this study, we show that molecular contacts of o-Dianisidine bis(diazotized) zinc double salt (bis diazo) on silicon (Si) can be made electrochemically and also spontaneously without the need of external electric field (Figure 1a) and can be potentially extended to other types of electrodes. The thin films were characterized electrochemically by spontaneously attaching ferreocene to the distal end of the bis diazo molecule and by using X-ray Photoelectron Spectroscopy (XPS), X-ray Reflectometry (XRR), Atomic Force Microscopy (AFM). Furthermore, electrochemical reduction of bis diazo molecule on different crystalline faces of Si were studied (Figure 1b). We found that Si <111> reduction wave occurs at more positive potential then that observed for Si <100>. To confirm these assignments we have created Si <111> pyramids on Si <100> surface by anisotropic etching in 20% KOH solution. By doing so, we have created a mixed <111/100> surface that can probe in-situ the difference in the electrochemical reduction between the two crystal faces (Figure 1 c). These types of diazonium salts could be used as molecular diodes, devices since they can spontaneously attach to both gold and silicon. References N. Darwish, M. N. Paddon-Row and J. J. Gooding, Acc. Chem. Res., 47, 385 (2013). N. Darwish, A. C. Aragonès, T. Darwish, S. Ciampi and I. Díez-Pérez, Nano Lett., 14, 7064 (2014). A. C. Aragonès, N. Darwish, S. Ciampi, F. Sanz, J. J. Gooding and I. Diéz-Pérez, Nat. Commun., 8 (2017). M. L. Perrin, E. Burzurí and H. S. J. van der Zant, Chem. Soc. Rev., 44, 902 (2015). Figure 1. a) Cyclic voltammogram of a thin film of bis diazo spontaneously grafted on n-type Si <111> (resting in a solution of bis diazo for 2 h on Si <111> surface and then exposed to a solution of ferreocene, scan at 0.2 V/s) b) Cyclic voltammetry of a the reduction of bis diazo on n-type Si <111> (red line (a)) and <100> (black line (b)) at scan rate 0.05 V/ s c) Potential difference in the electrochemical reduction between the two crystal faces on the pyramid surface . Figure 1