On the correlation between electronic intramolecular delocalization and Au-S bonding strength of ruthenium tetraammine SAMs

Trans-[Ru(L)(NH3)4(L')](PF6)n type complexes, where L = 4-cyanopyridine (CNpy), NCS-, CN-, and L' = CNpy, 1,4-dithiane (1,4-dt), 4-mercaptopyridine (pyS) and thionicotinamide (tna), were synthesized and characterized. SAMs on gold of the complexes containing sulfur were studied by reductive desorption and SERS spectroscopy. Depending on the nature of L', the withdrawing capability of the CNpy ligand is strong enough to partially oxidize the ruthenium atom and, as a consequence, delocalize the s electronic density from the trans located ligand. The reductive desorption results showed that the stability of the SAMs is directly related to this effect. (author)