The single molecule conductances of a series of bis-2,2':6',2 ''-terpyridine complexes featuring Ru(II), Fe(II), and Co(II) metal ions and trimethylsilylethynyl (Me3SiC C-) or thioinethyl (MeS-) surface Contact groups. have been determined. In the absence of electrochemical gating, these complexes behave as tunneling barriers, with conductance properties determined more by the strength of the electrode, molecule contact and the structure of the "linker" than the nature of the metal-ion or redox properties of the complex