Synthesis and the crystal and molecular structure of two modifications of bis(1,10-phenanthroline)trinitratoerbium(III) Er(NO3)3(Phen)2

Two crystalline modifications (I and II) of the phenanthroline complex of erbium nitrate with the same chemical composition, Er(NO₃)₃(Phen)₂, are synthesized by a procedure similar to that used for preparing the phenanthroline complexes of europium nitrate. The crystal structures of these modifications are determined using X-ray diffraction. Crystals of compound I belong to the isostructural family Ln(NO₃)₃(Phen)₂ (Ln = La-Lu). Crystals of compound II are isostructural to those of modification II (new phase) of the Eu(NO₃)₃(Phen)₂ compound. Crystals of I and II are monoclinic, space group C2/c, and Z = 4. The unit cell parameters are as follows: a = 11.126 Å, b = 17.815 Å, c = 12.976 Å, β = 100.45°, and V = 2529 ų for modification I and a = 9.459 Å, b = 15.463 Å, c = 17.076 Å, β = 93.52°, and V = 2493 ų for modification II. The molecular complexes in the structures of compounds I and II are nearly identical. The mean lengths of the Er-N and Er-O bonds are equal to 2.500 and 2.466 Å in compound I and 2.508 and 2.457 Å in compound II, respectively. The difference between the structures of compounds I and II is associated with the difference between intermolecular interactions in the unit cell.