Synthesis and structural determination of the first eight-coordinate rare earth metal complex with a six-member ring, (NH4)[EuIII(pdta)(H2O)] • H2O

(NH4)[Eu-III(pdta)(H2O)](H2O)-H-. has been synthesized and characterized by infrared spectrum, fluorescence spectrum, elemental analyses and single-crystal X-ray diffraction techniques. It crystallizes in the monoclinic system with space group P21/n, a = 12.7700(15)angstrom, b = 9.3885(11)angstrom, c = 14.4070(18)angstrom, alpha = 90 degrees, beta = 95.950(2)degrees, gamma = 90 degrees, V = 1718.0(4)angstrom(3), Z = 4, M = 508.28, D-c = 1.965 g cm(-3), mu = 3.708mm(-1), F(000) = 1108. The structure was refined to R-1 = 0.0238 for 3469 observed reflections (I > 2 sigma(I)). The (EuN2O6)-N-III part in the [Eu-III(pdta)(H2O)](-) complex anion has an eight-coordinate structure with a distorted square anti-prismatic conformation, in which six coordination positions, two nitrogen atoms and four oxygen atoms are from one pdta (=propylenediaminetetraacetic acid) ligand, the seventh position is an oxygen (O(8A)) from another pdta and the eighth coordination site is occupied by a water molecule. (NH4)[Eu-III(pdta)(H2O)](H2O)-H-. is the first eight-coordinate complex with a six-member ring in the rare earth metal complexes with aminopolycarboxylic acid ligands.