Olivia F. Koentjoro

Nanomechanical electron shuttle consisting of a gold nanoparticle embedded within the gap between two gold electrodes

Nanomechanical shuttles transferring small groups of electrons or even individual electrons from one electrode to another offer a novel approach to the problem of controlled charge transport. Here, we report the fabrication of shuttle-junctions consisting of a 20 nm diameter gold nanoparticle embedded within the gap between two gold electrodes. The nanoparticle is attached to the electrodes through a monolayer of flexible organic molecules which play the role of springs so that when a sufficient voltage bias is applied, then nanoparticle starts to oscillate transferring electrons from one electrode to the other. Current-voltage characteristics for the fabricated devices have been measured and compared with the results of our computer simulations.

Molecular rearrangements of diynes coordinated to triosmium carbonyl clusters: reactions of [Os3(μ-H)2(CO)10] and [Os3(CO)10(MeCN)2] with 1,4-dipyridylbuta-1,3-diyne

Reaction of [Os3(μ-H)2(CO)10] with 1,4-dipyridylbuta-1,3-diyne yields two clusters, [Os3(μ-H)(CO)10{μ-η1:η1-(C8H5N)–C–(C5H4N)}] 1 and [Os3(μ-H)(CO)10-{μ3-η1:η1:η1-(C5H4N)–C–C(C8H6N)}] 2, in which the diyne has rearranged to form a substituted indolizine ring system. Complex 1 converts slowly to 2 at room temperature, and may be decarbonylated to yield [Os3(μ-H)(CO)9{μ-η1:η2:η1-(C8H5N)–C–(C5H4N)}] 3. An analogous reaction involving [Os3(CO)10(MeCN)2] generates three products, [Os3(μ-H)(CO)10{μ-η1:η1-(NC5H3)–C2C2–(C5H5N)}] 4 and [{Os3(μ-H)(CO)10}2{μ-η1:η1-(NC5H3)–C2–}2] 5, both coordinated via orthometallated pyridyl rings, and a minor product [{Os3(CO)10}2{μ3-η1:η1:η1-C2-(NC5H4)}2] 6, coordinated via μ-carbene and σ-N interactions, the linking ligand retaining its central CC bond. Complex 4 reacts with [Os3(μ-H)2(CO)10] to form the linked cluster [{Os3(μ-H)(CO)10}2{μ-η1:η1,μ-η1:η1-(C8H5N)–C–(C5H3N)}] 7, also forming an indolizine ring system. The structures of 1–3, 6, 6·2[CH2Cl2] and 7 have been established by X-ray crystallography.

Experimental and Theoretical Investigation for the Level of Conjugation in Carbazole-Based Precursors and Their Mono-, Di-, and Polynuclear Pt(II) Complexes

A series of trimethylsilyl-protected monoalkynes (Me3SiC≡C-R) and bis-alkynes (Me3 SiC≡C-R-C≡CSiMe3) incorporating carbazole spacer groups (R = carbazole-2-yl, carbazole-3-yl, carbazole-2,7-diyl, N-(2-ethylhexyl)carbazole-2,7-diyl, carbazole-3,6-diyl, N-(2-ethylhexyl)carbazole-3,6-diyl), together with the corresponding terminal monoalkynes (H-C≡C-R) and bis-alkynes (H-C≡C-R-C≡C-H), have been synthesized and characterized. The CuI-catalyzed dehydrohalogenation reaction between trans-[(Ph)(Et3P)2PtCl], trans-[(Et3P)2PtCl2], and trans-[(P(n)Bu3)2PtCl2] and the terminal alkynes in (i)Pr2NH/CH2Cl2 affords a series of Pt(II) mono- and diynes, while the dehydrohalogenation polycondensation reactions with trans-[(P(n)Bu3)2PtCl2] under similar reaction conditions yields four Pt(II) poly-ynes of the form trans-[(P(n)Bu3)2Pt-C≡C-R-C≡C-]n. The acetylide-functionalized carbazole ligands and the mono-, di-, and polynuclear Pt(II) σ-acetylide complexes have been characterized spectroscopically, with a subset analyzed using single-crystal X-ray diffraction. The Pt(II) mono-, di-, and poly-ynes incorporating the carbazole spacers are soluble in common organic solvents, and solution absorption spectra show a consistent red-shift between the 2- and 2,7- as well as 3- and 3,6-carbazole complexes. Computational modeling is used to explain the observed spectral shifts, which are related to the enhanced electronic delocalization in the latter systems. These results also indicate that the inclusion of carbazole-2,7-diyl units into rigid-rod organometallic polymers should enhance electronic transport along the chains.