The distinct piezochromic luminescent responses of charge−transfer inclusion crystals, which consist of small aromatic guest molecules with naphthalenediimide derivatives, are reported. Reversible multichromism is observed over the entire visible region in response to high pressure, whereas a weak response to mechanical grinding is evident. High‐pressure single‐crystal X‐ray diffraction analysis and TD‐DFT calculations clearly suggest that high compression induces a closer arrangement with a short interfacial distance between small aromatic guest molecules and naphthalenediimide derivatives, which is proposed as the origin of the drastic luminescent color change.

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.

Benzothienobenzothiophene (BTBT) and derivatives have received increasing attention as organic field-effect transistor materials and molecular conductors. This report presents the first synthesis of metal complexes involving a BTBT moiety, which was achieved by complexation of 2,2′-bipyridyl complexes of Pt(II) and Pd(II) with dihydroxy-substituted BTBT (1) as a new π-extended catecholato ligand (^tBu₂Bpy = 4,4′-di-tert-butyl-2,2′-dipyridyl). The resulting complexes M(^tBu₂Bpy)(O₂BTBT) (M = Pt (3Pt) and Pd (3Pd)) were characterized by UV–vis spectroscopy, density functional theory (DFT) calculations, and cyclic voltammetry. The electron donating ability of BTBT was substantially enhanced upon including two oxygen substituents followed by metal coordination. This enabled chemical oxidation of 3Pt and 3Pd with a mild chemical oxidant (ferrocenium hexafluorophosphate) and formation of the one-electron-oxidized state. While 3Pt and 3Pd exhibited an absorption band originating from a catecholate → Bpy ligand-to-ligand charge transfer transition typical of this class of catecholato complexes, the radical cations exhibited a unique π–π* intramolecular charge transfer (ICT) transition absorption in which the π and π* orbitals were the newly incorporated benzothienothiophene-based donor and semiquinonato-based acceptor, respectively. The BTBT⁺ skeleton was electronically divided into two sites by the present chemical modification. The ICT properties of the complexes were found to be modulated by varying the metal ions. These findings offer a new approach to molecular design for (semi)conducting materials using optical properties.