A terminal ligand-substitution reaction at triruthenium redox centres within monolayer films is investigated. For this purpose, a new redox-active trinuclear ruthenium complex containing one carbonyl ligand at a terminal site, [Ru₃(O)(CH₃COO)₆(CO)(mpy)(C10PY)] (mpy = 4-methylpyridine, C10PY = {(NC₅H₄)CH₂NHC(O)(CH₂)₁₀S–}₂) 1, has been chemically adsorbed onto a gold electrode surface with a disulfide-alkyl spacer C10PY. Densely packed monolayers of complex 1 on Au electrodes (surface coverage, Γ(Ru₃) = 1.8 × 10⁻¹⁰ mol cm⁻²) display the {Ru^II–CO}Ru^IIIRu^III/{Ru^III–CO}Ru^IIIRu^III couple at E_1/2 = + 0.61 V s. Ag–AgCl in a 0.1 mol dm⁻³ HClO₄ aqueous solution. Upon electrochemical oxidation of the adsorbed complex at + 0.80 V, where the triruthenium carbonyl complex is in the oxidized form {Ru^III–CO}Ru^IIIRu^III, the coordinated CO is replaced by an aqua ligand present in the bulk phase, which is followed by cyclic voltammetry at appropriate electrolysis time intervals. During 8000 s of electrolysis, ca. 67% of the initially assembled carbonyl complexes are converted to the triruthenium aqua complexes, while ca. 25% desorbed from the electrode surface.

A catecholate-type artificial siderophore with a terminal-NH₂ group (1) and its Fe³⁺ complex (2) were prepared. Siderophore 1 was characterized by ¹H NMR, FT-IR, and ESI-TOF MS spectroscopy. The corresponding Fe³⁺ complex 2 was obtained by reaction of 1 with Fe(acac)₃. The absorption band at 500 nm (ε = 4670 M⁻¹ cm⁻¹ at pH 7.0) of the electronic absorption spectrum of 2 is assignable as the LMCT (O_catecholate → Fe³⁺) absorption band. This band indicates the formation of the Fe³⁺ complex of 1. The biological activity of 2 with respect to Escherichia coli was clearly confirmed by observing that it permeates into the cell membrane. The self-assembled monolayer of 2 on an Au substrate, 2/Au, was prepared and its preparation was confirmed by FT-IR reflection–absorption spectroscopy (IR-RAS) and cyclic voltammetry (CV). Furthermore, a quartz crystal microbalance (QCM) chip modified with 2 effectively adsorbed E. coli. M. flavescens, an organism which is incapable of synthesizing siderophores and must therefore use exogenous hydroxamate-type siderophores for growth, did not adsorb on 2/Au. In contrast, E. coli did not adsorb on the hydroxamate-type artificial siderophore–Fe³⁺ complex (3)-modified Au substrate, 3/Au. These results provide preliminary evidence that microbes recognized Fe³⁺ ion-bound siderophores on the surface. The detection limit of 2/Au was ∼10⁴ CFU mL⁻¹.

To develop low-cost and efficient dye-sensitized solar cells (DSSCs), we designed and prepared three homoleptic Cu(I) complexes with asymmetric ligands, M1, M2, and Y3, which have the advantages of heteroleptic-type complexes and compensate for their synthetic challenges. The three copper(I) complexes were characterized by elemental analysis, UV-vis absorption spectroscopy, and electrochemical measurements. Their absorption spectra and orbital energies were evaluated and are discussed in the context of TD-DFT calculations. The complexes have high V_OC values (0.48, 0.60, and 0.66 V for M1, M2, and Y3, respectively) which are similar to previously reported copper(I) dyes with symmetric ligands, although their energy conversion efficiencies are relatively low (0.17, 0.64, and 2.66%, respectively).

An unstable diiron(II,II) complex possessing O₂ binding ability at low temperature was encapsulated and stabilized in an ammonium-type ionic liquid layer polymerized on an electrode. The encapsulated complex revealed catalytic reactivity for four-electron reduction of O₂ at an ambient temperature in aqueous solution.

The liquid state of a bulky phosphonium-type ionic compound with a disulphide group was used to modify a Au substrate with effective dispersion. The substrate incorporates external compounds into the vacant space formed inside the ionic liquid regardless of the net charge of the compounds without any direct bonding.