Selective Two-Step Oxidation of μ₂-S Ligands in Trigonal Prismatic Unit {Re₃(μ₆-C)(μ₂-S)₃Re₃} of the Bioctahedral Cluster Anion [Re₁₂CS₁₇(CN)₆]^6–

An oxidation of cluster anion [Re₁₂CS₁₇(CN)₆]^6– by H₂O₂ in water has been investigated. It was shown that selective two-step oxidation of bridging μ₂-S-ligands in trigonal prismatic unit {Re₃(μ₆-C)­(μ₂-S)₃Re₃} takes place. The first stage runs rapidly, whereas the speed of the second stage depends on intensity of ultraviolet irradiation of the reaction mixture. Each stage of the reaction is accompanied by a change in the solution’s color. In the first stage of the oxidation, the cluster anion [Re₁₂CS₁₄(SO₂)₃(CN)₆]^6– is produced, in which all bridging S-ligands are turned into bridging SO₂-ligands. The second stage of the oxidation leads to formation of the anion [Re₁₂CS₁₄(SO₂)₂(SO₃)­(CN)₆]^6–, in which one of the SO₂-ligands underwent further oxidation forming the bridging SO₃-ligand. Seven compounds containing these anions were synthesized and characterized by a set of different methods, elemental analyses, IR and UV/vis spectroscopy, and quantum-chemical calculations. Structures of some compounds based on similar cluster anions, [Cu­(NH₃)₅]₃[Re₁₂CS₁₄(SO₂)₃(CN)₆]·9.5H₂O, [Ni­(NH₃)₆]₃[Re₁₂CS₁₄(SO₂)₃(CN)₆]·4H₂O, and [Cu­(NH₃)₅]_2.6[Re₁₂CS₁₄(SO₂)₃(CN)₆]_0.6[{Re₁₂CS₁₄(SO₂)₂(SO₃)­(CN)₅(μ-CN)}­{Cu­(NH₃)₄}]_0.4·5H₂O, were investigated by X-ray analysis of single crystals

Electroluminescence from a phthalocyanine monolayer encapsulated in a van der Waals tunnel diode

Monolayers of free base phthalocyanine (H2Pc) are grown on monolayer and few-layer exfoliated flakes of hexagonal boron nitride (hBN) which are subsequently integrated into a van der Waals tunnel diode. This heterostructure consists of two thin hBN flakes between which the H2Pc monolayer is sandwiched and also incorporates upper and lower few-layer graphene contacts. When a voltage is applied between the contacts, a tunnel current flows and the embedded molecules can be excited resulting in the emission of photons with wavelengths which are close to the peaks observed in photoluminescence. We also observe electroluminescence at voltages where the energy gained by a tunnelling electron is lower than the energy of the emitted photon implying a multi-electron excitation pathway which we attribute to the formation of an intermediate triplet state. Our results provide insights into the differences in excitation and relaxation of molecules in supramolecular monolayers and bulk crystals and we discuss how the alignment of the energy levels of the molecules and contact layers determine the emission process.</p