First Principles Studies of Molecular Junctions on the Basis of Tolane Derivatives

M. EZEQUIEL CASTILLO; P. VÉLEZ; M. E. ZOLOFF MICHOFF; E. P. M. LEIVA

Congreso; 65th Annual Meeting of the International Society of Electrochemistry; 2014

Density Functional Theory calculations are used to study the evolution of a variety of molecular systems (wires) attached to a gold nanolead, which is subjected to a pulling force. The nanowires analyzed in the present work are based on the diphenylacetylene structure (tolane), a molecule joining two benzene rings through an acetylene breach (HCCH). The head (or anchoring) groups studied involve the exchange of these benzenic rings of the base structure by each one of the following moieties: pyridyl (PY), tiophenol (SH), anyline (NH2), benzonitrile (CN) and dihydrobenzothiophene (BT1). These compunds have been lately studied for their conductive properties due to the conjugated π system.1 Energy and force profiles were obtained for the stretching process of the described systems. The results reveal that the starting geometry is crucial, as significant force values are not always found upon elongation of the junction. When meaningful forces are obtained, the following sequence (in descending order) of absolute forces is observed:SH > PY > CN > BT1 ~ NH2In order to consider the effect of the structure of the tip, we have repeated all the previous calculations with different geometries of its ending atoms.Conductance traces were calculated for several stretching processes. The trends observed are compared with the experimental results.