Molecular junctions of metal/molecule/metal were fabricated with silver nanoparticles and functional molecules through layer-by-layer self-assembly techniques. The Raman scattering of the interconnecting molecules between the silver nanoparticles can be greatly enhanced. For the silver/4-aminothiophenol/silver (Ag/PATP/Ag) assembly, in particular, the larger enhancement of the b 2 modes, relative to that of the a 1 modes, is ascribed to the charge transfer between the silver nanoparticles tunneling through the interconnecting PATP molecules. The molecular dipolar momentum and surface property of the silver nanoparticles have large effects on the enhancement of the Raman scattering of the interconnecting molecules.

Surface-enhanced Raman scattering (SERS) of the 4-mercaptopyridine (4-MPy) molecules adsorbed on the electrochemically roughened silver electrodes were investigated under practical electrochemical conditions. The adsorbed 4-MPy molecules are converted from a perpendicular orientation to a parallel orientation as the electrode potential is successively changed from 0 to -1.0 V. The coordination of the nitrogen atom of the pyridine ring to the silver metal weakens the ability of the 4-MPy molecules with a parallel orientation to capture the proton, because of the distribution of the electron density of the nitrogen to the silver metal. The applied potential has a large effect on the protonation/deprotonation process of the adsorbed 4-MPy molecules. More adsorbed 4-MPy molecules are protonated as the electrode potential becomes more negative. This is ascribed to the increase in the charge density on both the electrode surface and the nitrogen atom of the pyridine ring at the negative potentials.

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Surface-enhanced Raman scattering under near-IR excitation is investigated for p-aminothiophenol (PATP) molecules that are either adsorbed on an electrochemically roughened silver electrode or embedded in an Au/PATP/Ag molecular junction assembled on an indium-doped tin oxide electrode. The contribution from chemical enhancement can be amplified relative to the contribution from electromagnetic enhancement, because the energy of the near-IR excitation is far from the surface plasmon resonance of the nanosized metal particles. The energy required for the charge-transfer process for the Au/PATP/Ag molecular junction is much lower than that of the PATP molecules adsorbed on the electrochemically roughened silver electrode. Coadsorption of chloride ions on the metal nanoparticles may result in an alteration of the local Fermi level of the metal nanoparticles, thus leading to better energy matching between the energy level of the interconnecting PATP molecules and the Fermi level of the metal nanoparticles.

Hydrothermal reaction of olsalazine sodium, phenanthroline and Zn(ClO4)2·6H2O in the presence of water and ethanol affords a two‐dimensional coordination polymer [Zn4(OSA)3(Phen)2(H2O)2]n (1) (OSA = olsalazine) which is characterized by single X‐ray determination, IR and UV spectrum. The local coordination around all zinc ions can be best described as a slightly distorted triangle bipyramid. Complex 1 consists of a tetrameric subunit, which is made up of four Zn atoms bridged by four O atoms. Two types of osalazine ligands can be found in the complex according to their different coordination modes of carboxyl groups. Crystal data for 1: $\rm P{\bar 1}$, a = 10.087(7), b = 12.830(9), c = 14.545(11) Å, α =114.598(10)°, β = 92.552(10)°, γ = 108.515(10)°, V = 1588(2) Å3, Z = 2, R1 = 0.0818, wR2 = 0.1855. In comparison with the free ligand, the UV spectrum of 1 in solution (H2O: EtOH = 1:1) shows a small Einstein shift probably due to the formation of coordination polymer and supramoleculer hydrogen‐bonding interactions.