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Langenmaier, Michael; Rackl, Tobias; Johrendt, Dirk; Roehr, Caroline (2018): Alkali chalcogenido ortho manganates(II) A(6)MnQ(4) (A=Rb, Cs;Q = S, Se, Te). In: Zeitschrift für Naturforschung B, Journal of Chemical Sciences, Vol. 73, No. 11: pp. 837-848
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Abstract

The six isotypic alkali ortho chalcogenido manganates A(6)[Mn(II)Q(4)] (A=Rb, Cs;Q=5, Se, Te) were synthesized in most cases in pure phase from stoichiometric mixtures of the manganese monochalcogenides MnQ, the elemental chalcogens and Rb2S/Cs2S2 (sulfido salts) or the pure alkali elements (selenido and tellurido salts) as alkali sources at maximum temperatures between 650 and 800 degrees C. Their hexagonal crystal structures were refined by means of X-ray single crystal data (space group P6(3)mc, Na6ZnO4-type structure, Z=2;A/Q: Rb/S: a= 1019.34 (2), c= 792.560(10) pm, R1=0.0166;Rb/Se: a= 1055.74(2), c= 821.14(2) pm, R1= 0.0275;Rb/ Te: a =1126.68(2), c = 860.5/1(2) pm, R1=0.0152;Cs/S: a =1056.68(2), c= 831.22(2) pm, R1= 0.0168;Cs/Se: a=1096.04(3), c= 858.13(2) pm, R1= 0.0194;and Cs/Te: a=1167.72(3), c= 896.95(2) pm, R1=0.0140). The chiral structures contain isolated C-3 symmetric, but very close to ideal tetrahedral, ortho manganate(II) anions [Mn(II)Q(4)](6-) with Mn-Q distances of 248.7-250.7 (Q=S), 260.7-263.0 (Q=Se) and 280.0-282.4 pm (Q= Te). The chalcogenido ions form a hexagonal closed packing with slightly puckered 3(6) nets, in which the A(2) cations occupy 3/4 of the octahedral interstices, whereas Mn takes 1/8 and A(1) 3/8 of the tetrahedral voids. Magnetic measurements on the three Cs compounds showed Curie-Weiss behavior down to a temperature of 1.9 K, with magnetic moments significantly reduced with respect to the expected spinonly value of a d(5) ion. The electronic band structures of the four salts (Na/Rb)(6)Mn(S/Te)(4), which were calculated within the GGA+ U approach, allow a comparison of the chemical bonding characteristics and the magnetic properties within the alkali cation and the chalcogenido ligand series.