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)angstrom, b=19.143(4)angstrom, c=13.326(6)angstrom, β=128.15(4)degree, Z=4, Dx=3.14 Mg·m-3, T=296(1); and for Eu2(CrO4)3·7H2O, a=7.965(3)angstrom, b=18.985(4)angstrom, c=13.185(4)angstrom, β=128.00(2)degree, 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)angstrom, b=19.294(6)angstrom, c=13.436(8)angstrom, β=128.09(6)degree and those for Sm2(CrO4)3·7H2O are a=7.975(9)angstrom, b=19.00(1)angstrom, c=13.18(3)angstrom and β=127.5(2)degree. Thermal behavior was investigated and IR spectra were recorded for Ln2(CrO4)3·7H2O (Ln=La, Pr, Nd, Sm, Eu, Gd)