Synthesis, molecular structure and supramolecular chemistry of a new nickel-quinoxaline dithiolate system [Bu4N]2[Ni(6,7-qdt)2] (6,7-qdt = quinoxaline-6,7-dithiolate) and comparison of its electronic and electrochemical properties with those of [Bu4N]2[Ni

The new nickel bis(dithiolene) complex [Bu4N]2[Ni(6,7-qdt)2] (1) (6,7-qdt = quinoxaline-6,7-dithiolate) has been synthesized, starting from quinoxaline-6,7-dithiol, nickel chloride and tetrabutylammonium bromide in methanol. Compound 1 crystallizes in P21/c space group (monoclinic system). Its crystal structure has been characterized by interesting CH⋅⋅⋅S and CH⋅⋅⋅N weak interactions resulting in a three dimensional supramolecular network. Complex 1 shows solvent sensitive absorption band (broad feature) in the visible region, which is attributed to charge transfer (CT) transition involving electronic excitation from a HOMO that is a mixture of dithiolate (π) and metal (d) orbital character to a LUMO which is a π* orbital of the dithiolate. This CT transition absorbs at low energy region in comparison to the CT band of the [Bu4N]2[Ni(qdt)2] in the visible region. Interestingly, compound 1 undergoes reversible oxidation at very low oxidation potential (E1/2 = + 0.12 V vs Ag/AgCl) compared to that of [Ni(qdt)2]2− (E1/2 = + 0.41 V vs Ag/AgCl) in MeOH solutions.

Graphical AbstractA new nickel-bis(dithiolene) complex [Bu4N]2[Ni(6,7-qdt)2] (1) (6,7-qdt = quinoxaline-6,7-dithiolate) has been synthesized and characterized. Its electronic absorption and electrochemical properties are discussed in comparison with those of [Bu4N]2[Ni(qdt)2] complex.Figure optionsDownload as PowerPoint slideResearch Highlights
► A new nickel bis(dithiolene) complex has been synthesized based on quinoxaline-6,7-dithiolate.
► Its crystal structure has been characterized by C–H···S and C–H···N weak interactions.
► The title compound undergoes reversible oxidation at a very low oxidation potential.