Crystal and molecular structure of the coordination compounds of Er³⁺ with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [ErL2¹ (NO3)2]2[Er(NO3)2(H2O)5]0.333(NO3)2.333 · 2.833H2O and its ethyl substituted derivative [ErL 2² (NO3)2][Er(NO3)5]0.5 · 0.5H2O

The coordination compounds of Er3+ with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [ErL21(NO3)2]2[Er(NO3)2(H2O)5]0.333(NO3)2.333 · 2.833H2O (I) and its ethyl substituted derivative [ErL22(NO3)2][Er(NO3)5]0.5 · 0.5H2O (II) are synthesized and their crystal structures are studied. I and II contain [ErL2(NO3)2]+ complex cations of identical composition and close structure. The eight-vertex polyhedron of the Er atom in the shape of a distorted octahedron with two split trans vertices is formed by the O atoms of the phosphoryl groups of L ligands and nitrate anions. L ligands close nine-membered metallocycles. The structures contain spacious channels which are populated differently, namely, by disordered [Er(NO3)2(H2O)5]+ complex cations, NO3− anions, and crystallization water molecules in I and disordered [Er(NO3)5]2− complex anions and crystallization water molecules in II. The IR spectra of I and II are studied.