Luminescent acetylthiol derivative tripodal osmium(II) and iridium(III) complexes: Spectroscopy in solution and on surfaces*

Luminescent Os(II) and Ir(III) complexes containing a tripodal-type structure ter- minalized with three thiol derivatives are described. The tripod is introduced through deriva- tization, with a rigid spacer, of a phenanthroline ligand coordinated to the metal ion, and the entire structure possesses axial geometry. The geometry of the complexes combined with the three anchoring sites, the thiol groups, allows the complexes to adopt an almost perpendicu- lar arrangement to the surfaces and the formation of a well-packed monolayer on Au sub- strates. The photophysical and electrochemical behavior of the complexes is studied in solu- tion and on surfaces. Furthermore, a self-assembled monolayer (SAM) of Os(II) complexes on an ultraflat Au surface is used to fabricate a metal-molecule-metal junction with Au and In Ga eutectic as electrodes. The Os(II) SAM in the tunneling junction exhibits rectification behavior which is opposite in direction to that which we have previously shown for Ru(II) SAMs.