Two Electrocatalytic Selenoarsenates with Manganese Complex Cations as Counterions

The discovery of new organic hybrid chalcogenidometalates is of great importance for structural chemistry and functional material. Here, new types of organic hybrid selenoarsenates [Mn(dien)₂]₂[As^II₄Se₆] (1, dien = diethylenetriamine) and [Mn(dien)₂]₂[Mn(As^IIISe₃)₂] (2) have been solvothermally synthesized by the reaction of K₃AsO₃, Se, and MnCl₂·xH₂O (x = 0, 2) in dien solution at 120 °C. 1 presents a hitherto unknown [As^II₄Se₆]^4- anion with low-valent As²⁺ ion, which comprises a centrosymmetric six-membered [As^II₄Se₂] ring in chair-like conformation, while 2 contains a new type of heterometallic selenoarsenate(III) [Mn(As^IIISe₃)₂]^4- constructed by the connection of one tetrahedral [MnSe₄] and two rare noncondensed [As^IIISe₃]^3- anions. 1 and 2 were first combined with nickel nanoparticle (Ni) and the nickel foam (NF) for fabricating the 1/Ni/NF and 2/Ni/NF electrodes, which exhibited excellent oxygen evolution reaction electrocatalytic property with a low overpotential of 248 mV for 1 and 219 mV for 2 at 10 mA cm^-2 in alkaline media.