Electrical conductance through conjugated biphenyl and saturated alkane molecules on gold electrodes is characterized using a molecule/nanoparticle/molecule electrical test-bed assembly, and comparisons are made between molecules containing isocyanide (-NC) and thiol (-S) terminal groups bound to the gold. Current versus voltage analysis is consistent with charge tunneling through all systems studied. For molecules containing biphenyl, diphenyl acetylene, and alkane bridges, those containing an isocyanide terminal group show an order of magnitude increase in conductance as compared to those containing a thiol terminal group. Various theoretical predictions of the effect of isocyanide terminal groups on charge transfer through conjugated molecular systems are discussed and related to the results observed for charge transfer through conjugated and saturated molecules. The similar trends in charge transport observed for the different metal/linker interfaces suggest that the metal/linker contact plays an important role in interface electronic structure, even when the molecules are expected to have very different electron delocalization across the backbone.

Deprotonation of the phosphine complexes Au(PHR2)Cl with aqueous ammonia gave the gold(I) phosphido complexes [Au(PR2)] n (PR2 = PMes2 (1), PCy2 (2), P(t-Bu)2 (3), PIs2 (4), PPhMes (5), PHMes* (6); Mes = 2,4,6-Me3C6H2, Is = 2,4,6-(i-Pr)3C6H2, Mes* = 2,4,6-(t-Bu)3C6H2, Cy = cyclo-C6H11). 31P NMR spectroscopy showed that these complexes exist in solution as mixtures, presumably oligomeric rings of different sizes. X-ray crystallographic structure determinations on single oligomers of 1−4 revealed rings of varying size (n = 4, 6, 6, and 3, respectively) and conformation. Reactions of 1−3 and 5 with PPN[AuCl2] gave PPN[(AuCl)2(μ-PR2)] (9−12, PPN = (PPh3)2N+). Treatment of 3 with the reagents HI, I2, ArSH, LiP(t-Bu)2, and [PH2(t-Bu)2]BF4 gave respectively Au(PH(t-Bu)2)(I) (14), Au(PI(t-Bu)2)(I) (15), Au(PH(t-Bu)2)(SAr) (16, Ar = p-t-BuC6H4), Li[Au(P(t-Bu)2)2] (17), and [Au(PH(t-Bu)2)2]BF4 (19).

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