Substituent effect on the mechanical properties of Au-N nanojunctions
ZOLOFF MICHOFF; P. VÉLEZ; E. P. M. LEIVA
JOURNAL OF PHYSICAL CHEMISTRY C
AMER CHEMICAL SOC
Año: 2008 vol. 113 p. 3850 - 3854
We report on the calculated binding energies and rupture forces of a series of ortho-substituted pyrazines bonded to gold nanoclusters. This system is proposed as a model for the 4,4-bipyridine−gold nanojunction to assess the effect of the substituent on the mechanical stability and the rupture modes of such nanojunction. The present results show that although there is a definite trend to a reduced rupture force for a more electron withdrawing substituent on the pyrazine molecule, this dependence is small, allowing for the construction of nanojunctions with different transport properties but similar mechanical stabilities. A clear-cut correlation is found between the rupture force of the nanojunction and the pKa value of the structurally related pyridines, providing with a simple empirical way of predicting the stability of the system. The possibility of attaching the molecule to the cluster through a monatomic gold chain is also explored, with the finding that the Au−Au rupture at the chain is a possible mechanism when the chain is at least two atoms long.