Developing molecular circuits that can function as the active components in electrical devices is an ongoing challenge in molecular electronics. It demands mechanical stability of the single-molecule circuit while simultaneously being responsive to external stimuli mimicking the operation of conventional electronic components. Here, we report single-molecule circuits based on spiropyran derivatives that respond electrically to chemical and mechanical stimuli. The merocyanine that results from the protonation/ ring-opening of the spiropyran form showed single-molecule diode characteristics, with an average current rectification ratio of 5 at ±1 V, favoring the orientation where the positively charged end of the molecule is attached to the negative terminal of the circuit. Mechanical pulling of a single spiropyran molecule drives a switch to a more conducting merocyanine state. The mechanical switching is enabled by the strong Au−C covalent bonding between the molecule and the electrodes, which allows the tensile force delivered by the STM piezo to break the molecule at its spiropyran C−O bond.

This paper describes the syntheses of several functionalized dihydropyrene (DHP) molecular switches with different substitution patterns. Regioselective nucleophilic alkylation of a 5-substituted dimethyl isophthalate allowed the development of a workable synthetic protocol for the preparation of 2,7-alkyne-functionalized DHPs. Synthesis of DHPs with surface-anchoring groups in the 2,7- and 4,9-positions is described. The molecular structures of several intermediates and DHPs were elucidated by X-ray single-crystal diffraction. Molecular properties and switching capabilities of both types of DHPs were assessed by light irradiation experiments, spectroelectrochemistry, and cyclic voltammetry. Spectroelectrochemistry, in combination with density functional theory (DFT) calculations, shows reversible electrochemical switching from the DHP forms to the cyclophanediene (CPD) forms. Charge-transport behavior was assessed in single-molecule scanning tunneling microscope (STM) break junctions, combined with density functional theory-based quantum transport calculations. All DHPs with surface-contacting groups form stable molecular junctions. Experiments show that the molecular conductance depends on the substitution pattern of the DHP motif. The conductance was found to decrease with increasing applied bias.

Multifunctional switches are crucial to the development of smart molecular materials and molecular-electronic applications. Here, we describe the synthesis, structure, and characterization of several spiropyrans functionalized with alkynyl-[Ru(dppe)2] moieties. Through...

Ruthenium half-sandwich complexes are central in a wide range of diverse applications in the field of organometallic chemistry. As such, exploration of their preparation and reactivity is crucial for development of their chemistry. Herein, we present alternative synthetic methods for the preparation of Cp*Ru(dppm)Cl, Cp*Ru(dppe)Cl, Cp*Ru(dppf)Cl, [Cp*Ru(COD)(MeCN)]BF4, and [Cp*Ru(bpy)(MeCN)]BF4 (dppm = 1,2-bis(diphenylphosphino)methane; dppe = 1,2-bis(diphenylphosphino) ethane; dppf = 1,2-bis(diphenylphosphino)ferrocene; COD = 1,5-cyclooctadiene; bpy= 2,2′-bipyridine), starting from the easily accessible [Cp*Ru(η6-C10H8)]BF4. The single-crystal X-ray structure determinations for [Cp*Ru(COD)(MeCN)]BF4, and [Cp*Ru(bpy)(MeCN)]BF4 are also presented.

The modification of conjugated organic compounds with organometallic moieties allows the modulation of the electronic and optoelectronic properties of such compounds and lends them to a variety of material applications. The organometallic complexes [M(Cp′)(L)n] (M = Ru or Fe; Cp′ = cyclopentadiene (Cp) or pentamethylcyclopentadiene (Cp*); (L)n = (PPh3)2 or 1,2-bi(diphenylphosphino)ethane (dppe)) and [M(L)n] (M = Ru; (L)n = (dppe)2 or (P(OEt)3)4; or M = Pt; (L)n = (PEt3)2, (PPh3)2 or tricyclohexylphosphine, (PCy3)2) modified with a 5-ethynyl-1,3,3-trimethyl-3H-indole ligand were prepared and characterised by NMR spectroscopy, IR and single-crystal X-ray diffraction. Cyclic voltammetry and IR spectroelectrochemistry of the ruthenium systems showed a single-electron oxidation localised over the M–C≡C–aryl moiety. The N-heteroatom of the indole ligand showed Lewis base properties and was able to extract a proton from a vinylidene intermediate as well as coordinate to CuI. Examples from the wire-like compounds were also studied by single-molecule break junction experiments but molecular junction formation was not observed. This is most likely attributable to the binding characteristics of the substituted terminal indole groups used here to the gold contacts.