Incorporation of A2Q into HgQ and dimensional reduction to A2Hg3Q4 and A2Hg6Q7 (A = K, Rb, Cs; Q = S, Se). Access of Li ions in A2Hg6Q7 through topotactic ion-exchange

Enos A. Axtell, Younbong Park, Konstantinos Chondroudis, Mercouri G. Kanatzidis

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Abstract

The synthesis of the one-dimensional K2Hg3Q4 (Q = S, Se) and Cs2Hg3Se4 and the three-dimensional A2Hg6S7 (A = K, Rb, Cs), and A2Hg6Se7 (A = Rb, Cs) in reactive A2Q(x) fluxes is reported. Pale yellow, hexagonal plates of K2Hg3S4 crystallize in space group Pbcn, with a = 10.561(5) Å, b = 6.534(3) Å, and c = 13.706(2) Å, V = 945.8(7) Å,3 d(calc) = 5.68 g/cm3, and final R = 5.7%, R(w) = 6.3%. Red, hexagonal plates of K2Hg3Se4 crystallize in space group Pbcn, with a = 10.820(2) Å, b = 6.783(1) Å, and c 14.042(2) Å, v = 1030.6(5) Å,3 d(calc) = 6.42 g/cm3, and final R = 7.7%, R(w) = 8.4%. Orange yellow, hexagonal plates of Cs2Hg3Se4 crystallize in space group Pbcn, with a = 12.047(4) Å, b = 6.465(2) Å, and c = 14.771(6) Å, V = 1150.4(7) Å, 3 d(calc) = 6.83 g/cm3, and final R = 5.5%, R(w) = 6.2%. Black needles of K2Hg6S7 crystallize in space group P421m, with a = 13.805(8) Å and c = 4.080(3) Å, V = 778(1) Å, 3 d(calc) = 6.43 g/cm3, and final R = 3.1%, R(w) 3.6%. Black needles of Rb2Hg6S7 crystallize in space group P42nm, with a = 13.9221(8) Å and c = 4.1204(2) Å, V = 798.6(1) Å, 3 d(calc) = 6.65 g/cm3, and final R = 4.3%, R(w) = 5.0%. Black needles of Cs2Hg6S7 crystallize in space group P42nm, with a = 13.958(4) Å and c = 4.159(2) Å, V = 810.2(8) Å, 3 d(calc) = 6.94 g/cm3, and final R = 4.3%, R(w) = 4.4%. Black needles of Cs2Hg6Se7 crystallize in space group P42nm, with a = 14.505(7) Å and c = 4.308(2) Å, V = 906(1) Å, 3 d(calc) = 7.41 g/cm3, and final R = 3.6%, R(w) = 4.0%. The A2Hg3Q4 compounds Contain linear chains. The A2Hg6Q7 compounds display noncentrosymmetric frameworks with A+ cations residing in tunnels formed by both tetrahedral and linear Hg atoms. K2Hg6S7, Rb2Hg6S7, Cs2Hg6S7, Rb2Hg6Se7, and Cs2Hg6Se7 display room-temperature bandgaps of 1.51, 1.55, 1.61, 1.13, and 1.17 eV, respectively. Bandgap engineering through S/Se solid solutions of the type Rb2Hg6Se(7-x)S(x) and Cs2Hg6Se(7-x)S(x) is possible in-these materials. All A2Hg6Q7 melt congruently, with melting points of 556 ± 10 °C, except for Rb2Hg6Se7 which degrades. Rb2Hg6S7 can undergo ion exchange reactions with LiI to give Li1.8Rb0.2Hg6S7.

Original languageEnglish
Pages (from-to)124-136
Number of pages13
JournalJournal of the American Chemical Society
Volume120
Issue number1
DOIs
Publication statusPublished - Jan 14 1998

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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