Novel thioarsenates {[Mn(2,2′-bipy)2(SCN)][Mn(2,2′-bipy)](AsVS4)}2 and {[Mn(2,2′-bipy)2(SCN)]2[AsIII2(S2)2S2]}: introducing an anionic second ligand to modify MnII complex cations of 2,2′-bipyridine

Abstract

Two novel manganese thioarsenates, {[Mn(2,2′-bipy)₂(SCN)][Mn(2,2′-bipy)](As^VS₄)}₂ (1, 2,2′-bipy = 2,2′-bipyridine) and {[Mn(2,2′-bipy)₂(SCN)]₂[As^III₂(S₂)₂S₂]} (2), containing thiocyanate-modified Mn-2,2′-bipy complex cations were synthesized. They feature two terminal [Mn(2,2′-bipy)₂(SCN)]⁺ complex cations bridged by a polyanion {[Mn(2,2′-bipy)]₂(As^VS₄)₂}²⁻ for 1 and a cyclic thioarsenate anion (As^III₂S₆)²⁻ for 2. In 2, the [As^III₂(S₂)₂S₂]²⁻ anion can be described as two (As^IIIS₃)³⁻ trigonal-pyramids interlinked through S–S bonds. The method to obtain new metal complex cations shown here, introducing an anionic second ligand to modify the number of coordination sites and the charges of the metal complex cations simultaneously, is different from the traditional methods, varying either the TM center or the organic ligand or employing mixed neutral organic ligands, and may open up a new route for preparing novel chalcogenidometalates. Compounds 1 and 2 exhibit wide optical gaps of 2.20 and 2.67 eV, respectively, and photoluminescence with the emission maxima occurring around 440 nm. Magnetic measurements show the presence of antiferromagnetic interactions between Mn^II centers in the two compounds.