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)

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 P21 c. For Nd2(CrO4)3 · 7H2O, a = 8.052(4) Å, b = 19.143(4) Å, c = 13.326(6) Å, 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) Å, b = 18.985(4) Å, c = 13.185(4) Å, 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) Å, b = 19.294(6) Å, c = 13.436(8) Å, β = 128.09(6)° and those for Sm2(CrO4)3 · 7H2O are a = 7.975(9) Å, b = 19.00(1) Å, c = 13.18(3) Å 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). © 1991.