Reactivity of chalcogenostannate compounds: syntheses, crystal structures, and electronic properties of novel compounds containing discrete ternary anions [MII4(mu4-Se)(SnSe4)4]10- (MII = Zn, Mn).

Reactions of K4[SnSe4].1.5MeOH with ZnCl2 or MnCl2.4H2O in water/methanol mixtures yield novel compounds [K10(H2O)16(MeOH)0.5][M4(mu4-Se)(SnSe4)4] (M = Zn, 2; Mn, 3) in high yields; 2 and 3 contain the first discrete ternary Zn/Sn/Se or Mn/Sn/Se cluster anions. Both compounds were unambiguously characterized by X-ray diffraction (tetragonal, space groups P43212 and P41212, respectively) revealing chiral anionic structures within chiral crystals. Optical spectra of 2 and 3 indicate energy differences for the lowest electronic excitations (Eg = 2.57 eV, 2; 2.27 eV, 3) that are very close to the band gap values observed for mesoporous solids with polymeric M/Sn/E networks. DFT investigations on the electronic situation and first ESR studies agree in that they demonstrate a high-spin ground state in the case of 3 with 20 unpaired electrons at four uncoupled MnII centers.