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RESEARCH PRODUCT

The crystal structure of neodymium and europium chromate heptahydrate: Synthesis, infrared spectra, and thermal behavior of lanthanoid chromate heptahydrates, [Ln2(CrO4)3(H2O)5] · 2H2O (Ln = La, Pr, Nd, Sm, Eu, Gd)

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Abstract The crystal structures of Nd2(CrO4)3 · 7H2O and Eu2(CrO4)3 · 7H2O were determined by the conventional single-crystal X-ray diffraction technique. In addition, unit cell dimensions were measured for La2 (CrO4)3 · 7H2O and Sm2(CrO4)3 · 7H2O. All these compounds are isostructural. Crystals are monoclinic, space group P2 1 c . For Nd2(CrO4)3 · 7H2O, a = 8.052(4) A, b = 19.143(4) A, c = 13.326(6) A, β = 128.15(4)°, Z = 4, Dx = 3.14 Mg · m−3, T = 296(1); and for Eu2(CrO4)3 · 7H2O, a = 7.965(3) A, b = 18.985(4) A, c = 13.185(4) A, β = 128.00(2)°, Z = 4, Dx = 3.29 Mg · m−3, T = 296(1). Ln atoms are nine-coordinated so that the coordination polyhedron is a tricapped trigonal prism for Ln1 and a monocapped square antiprism for Ln2. Structures form a three-dimensional network. Unit cell dimensions for La2(CrO4)3 · 7H2O are a = 8.181(6) A, b = 19.294(6) A, c = 13.436(8) A, β = 128.09(6)° and those for Sm2(CrO4)3 · 7H2O are a = 7.975(9) A, b = 19.00(1) A, c = 13.18(3) A and β = 127.5(2)°. Thermal behavior was investigated and IR spectra were recorded for Ln2(CrO4)3 · 7H2O (Ln = La, Pr, Nd, Sm, Eu, Gd).