Potential feedback: Metallic electrodes with controlled gap widths ranging from about 10 nm down to several angstroms (as determined by SEM measurements) can be fabricated electrochemically by using a simple potential feedback system with a unique electrode configuration (see picture). The working principle is based on the potential distribution in the electric double‐layer. The process is simple, controllable, and reproducible.

Treatment of [OsCl(2)(PPh(3))(3)] with HC[triple bond]CCH(OH)C[triple bond]CH/PPh(3) produces the osmabenzene [Os{CHC(PPh(3))CHC(PPh(3))CH}Cl(2)(PPh(3))(2)][OH] (2), which is air stable in both solution and solid state. The key intermediate of the one-pot reaction, [OsCl(2){CH=C(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (3), and the related complex [Os(NCS)(2){CHC(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (7) have been isolated and characterized, further supporting the proposed mechanisms for the reaction. Reactions of 3 with PPh(3), NaI, and NaSCN give osmabenzene 2, iodo-substituted osmabenzene [Os{CHC(PPh(3))CHCICH}I(2)(PPh(3))(2)] (4), and thiocyanato-substituted osmabenzene [Os{CHC(PPh(3))CHC(SCN)CH}(NCS)(2)(PPh(3))(2)] (5) respectively. Similarly, reaction of [OsBr(2)(PPh(3))(3)] with HC[triple bond]CCH(OH)C[triple bond] CH in THF produces [OsBr(2){CH=C(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (9), which reacts with PPh(3)/Bu(4)NBr to give osmabenzene [Os{CHC(PPh(3))CHC(PPh(3))CH}Br(2)(PPh(3))(2)]Br (10). Ligand substitution reactions of 2 produce a series of new stable osmabenzenes 11-17. An electrochemical study shows that osmabenzenes 2, 12, and 14-17 have interesting different electrochemical properties due to the different co-ligand. The oxidation potentials of complexes 2, 12, 16, and 17 with Cl, NCS, and N(CN)(2) ligands gradually positively shift in the sequence of Cl

Reproducible fabrication of sharp gold- or silver-coated tips has become the bottleneck issue in tip-enhanced Raman spectroscopy, especially for atomic force microscopy (AFM)-based TERS. Herein, we developed a novel method based on pulsed electrodeposition to coat a thin gold layer over atomic force microscopy (AFM) tips to produce plasmonic TERS tips with high reproducibility. We systematically investigated the influence of the deposition potential and step time on the surface roughness and sharpness. This method allows the rational control of the radii of gold-coated TERS tips from a few to hundreds of nanometers, which allows us to systematically study the dependence of the TERS enhancement on the radius of the gold-coated AFM tip. The maximum TERS enhancement was achieved for the tip radius in the range of 60-75 nm in the gap mode. The coated gold layer has a strong adhesion with the silicon tip surface, which is highly stable in water, showing the great potential for application in the aqueous environment.

Treatment of RuCl2(PPh3)3 with HC⋮CCH(OH)C⋮CH/PPh3 at room temperature produces the air-stable ruthenabenzene [Ru(CHC(PPh3)CHC(PPh3)CH)Cl2(PPh3)2]Cl (2) in good yield. The ruthenabenzene 2 can even be obtained from the one-pot reaction of RuCl3, PPh3, and HC⋮CCH(OH)C⋮CH in the mixed solvent of ionic liquid and CH2Cl2 in higher yield. The ruthenabenzene 2 reacts with PMe3, PBu3, tert-butyl isocyanide, 2,2‘-dipyridyl (bipy), and 2,2‘-dipyridyl/PMe3 to give new stable ruthenabenzenes [Ru(CHC(PPh3)CHC(PPh3)CH)Cl2(PMe3)2]Cl (4), [Ru(CHC(PPh3)CHC(PPh3)CH)Cl2(PBu3)2]Cl (5), [Ru(CHC(PPh3)CHC(PPh3)CH)Cl( t BuNC)(PPh3)2]Cl2 (6), [Ru(CHC(PPh3)CHC(PPh3)CH)Cl(bipy)(PPh3)]Cl2 (7), and [Ru(CHC(PPh3)CHC(PPh3)CH)(bipy)(PMe3)2]Cl3 (8), respectively. Reaction of ruthenabenzene 2 with AgBF4 gives bisruthenabenzene [Ru(CHC(PPh3)CHC(PPh3)CH)(PPh3)]2(μ-Cl)3(BF4)3 (9). The thermal decomposition reactions of ruthenabenzene 2 and 7 produce a stable Cp- ion derivative, [CHC(PPh3)CHC(PPh3)CH]Cl (10). 2, 4, 7, 8, 9, and 10 have been structurally characterized. 9 is the first non-metal-coordinated bismetallabenzene. An electrochemical study shows that the metal centers in the bisruthenabenzene 9 slightly interact with each other through the chloro bridges.