A lead(ii)–N′-isonicotinoylpyrazine-2-carbohydrazonamide complex system as a converter of aerial carbon dioxide to carbonate under electrochemical conditions with the formation of a single-component white light-emitting phosphor

Abstract

In this contribution, a novel binuclear heteroleptic complex [Pb₂L₂(CO₃)]·2CH₃CN·2MeOH (1·2CH₃CN·2MeOH) is reported, which was fabricated by electrochemical oxidation of a lead anode under an ambient atmosphere in a CH₃CN : MeOH solution of N′-isonicotinoylpyrazine-2-carbohydrazonamide (HL). The CO₃²⁻ anion was produced from the conversion of aerial CO₂ by the Pb²⁺–L complex system under electrochemical conditions. In the structure of 1, ligand L exhibits a tridentate pincer-like N,N′,O-coordination mode, while the CO₃²⁻ anion exhibits a tetradentate bridging coordination mode with one of the oxygen atoms exhibiting a bridging μ-coordination mode. The metal cations in the structure of 1 are in a five-membered N₂O₃ coordination environment, formed by covalent bonds. The molecular structure of 1·2CH₃CN·2MeOH is stabilized by a pair of intermolecular Pb⋯N tetrel bonds formed with one of the NH₂ nitrogen atoms of an adjacent complex molecule and with the acetonitrile nitrogen atom, and one Pb⋯O tetrel bond formed with the carbonyl oxygen atom of the other adjacent complex molecule, yielding a 2D supramolecular sheet. This sheet is further stabilized by intermolecular N–H⋯N_acetonitrile and N–H⋯O_carbonate hydrogen bonds and π_Pyrazine⋯π_Pyridine interactions. The optical properties of the complex were revealed by UV-vis spectroscopy and spectrofluorimetry in MeOH. It was established that the described complex is emissive upon excitation at 340 nm with a broad band from about 500 nm to 780 nm with a maximum at ∼580 nm, accompanied by a shoulder at ∼620 nm. The CIE-1931 chromaticity coordinates of (0.28, 0.36) fall within the white gamut of the chromaticity diagram. Thus, complex 1 is a single-component white light-emitting phosphor.