Modulation of the Conductance in Platinum(II) Bis(acetylide) Molecules through “Gating” Metal Ion
Mononuclear platinum(II) complex trans-Pt(PPh3)2(CCC6H4SMe-4)2 (1-Pt) and its derivatives [PtM(dppm)2(CCC6H4SMe-4)2]+ (dppm = bis(diphenylphosphino)methane; M = Au, 2-PtAu; Ag, 2-PtAg; Cu, 2-PtCu) with “mono-gating” metal ion and [PtM2(dpmp)2(CCC6H4SMe-4)2]2+ (dppm = bis(diphenylphosphinomethyl)phenylphosphine; M = Au, 3-PtAu2; Ag, 3-PtAg2) with “dual-gating” metal ions were elaborately designed to modulate the conductance in platinum(II) bis(-acetylide) complexes through “gating” d10 metal ion. The single-molecule conductance measurements by STM-BJ technique demonstrate that the conductance follows 10-4.5 (1-Pt) > 10-4.8 (2-PtAu) > 10-4.9 (2-PtAg) > 10-5.0 (2-PtCu) > 10-5.1 (3-PtAu2) > 10-5.3 (3-PtAg2) G0. Undoubtedly, charge transport along platinum(II) bis(-acetylide) backbone is progressively restricted with introducing one to two “gating” M ions to mononuclear platinum(II) molecule. As revealed by X-ray crystallography, the “gating” d10 metal ion is substantially bound to the acetylide and in fact the Macetylide bonding is progressively enhanced following AuCacetylide AgCacetylide CuCacetylide, which coincides to a progressive decrease of the conductance according to 10-4.8 (2-PtAu) > 10-4.9 (2-PtAg) > 10-5.0 (2-PtCu) G0. The Macetylide coordination blocks charge transport along platinum(II) bis(-acetylide) backbone so that d10 metal ion behaves as a resistance to suppress the conductance. Theoretical studies confirm that the “gating” metal ions control the HOMO energy, which is lowered by the increased d orbital contribution of “gating” metal ions through Pt-M interactions.