Structural Diversity of Rare Earth Bromide Complexes with Acetylurea

New coordination compounds of light rare-earth bromides with acetylurea (AsUr) have been synthesized, namely [Y(AcUr)(2)(H2O)(4)](1.39)[Y(AcUr)(2)(H2O)(5)](0.61)Br-6 center dot 2H(2)O (I), [La(AcUr)(2)(H2O)(5)]Br-3 (II), [Ce(AcUr)(2)(H2O)(5)]Br-3 (III), [Nd(AcUr)(2)(H2O)(5)]Br-3 (IV), and [Sm(AcUr)(2)(H2O)(5)]Br-3 (V). Their compositions and structures have been determined by elemental analysis, IR spectroscopy, and X-ray diffraction. It has been found that compound I is built of the [Y(AcUr)(2)(H2O)(4)](3+) and [Y(AcUr)(2)(H2O)(5)](3+) cations in the 2.28 : 1 ratio; they differ by the number of the inner-sphere water molecules (4 and 5 for coordination numbers 8 and 9, respectively), non-coordinated Br- ions, and H2O molecules. Compounds II and III are built of the [Ln(AcUr)(2)(H2O)(5)](3+) (Ln = La, Ce) cations and outer-sphere Br-ions. The structures change when cooling from 296 K to 100 K being isostructural at both temperatures. Compounds IV and V have the same composition, but other structures. They also have different polymorphous modifications at 100 and 296 K. Samarium, terbium, and dysprosium bromide complexes of acetyl urea show photoluminescence.