Syntheses, structural determination, and binding studies of nine-coordinate mononuclear complexes (EnH2)3[EuIII(Etha)]2 · 11H2O and (EnH2)[EuIII(Egta)(H2O)]2 · 6H2O

Two novel ethylenediaminium salt of europium complexes with aminopolycarboxylic acid ligands, (EnH2)3[EuIII(Ttha)]2 · 11H2O (I) (En is ethylenediamine, H6Ttha is triethylenetetramine-N,N,N′,N″,N‴,N‴-hexaacetic acid) and (EnH2)[EuIII(Egta)(H2O)]2 · 6H2O (II) (H4Egta is ethyleneglycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid) complexes were synthesized, and their crystal structures were determined by single-crystal X-ray diffraction techniques. Both of the two complexes adopt nine-coordinate structures with the pseudo-monocapped square antiprism and crystallize in the monoclinic crystal system with the P21/n space group. The crystal data for complex I are as follows: a = 17.8262(8), b = 19.3137(5), c = 20.6233(8) A, β = 111.301(2)°, V = 6615.3(4) A3, Z = 8, ρ c = 1.677 mg/m3, μ = 1.981 mm−1, F(000) = 3432, R = 0.0308, and wR = 0.0737 for 43622 observed reflections with I ≥ 2σ(I). The crystal data for complex II are as follows: a = 12.952(3), b = 12.618(2), c = 14.809(3) A, β = 105.695(2)°, V = 2330.0(8) A3, Z = 4, ρ c = 1.800 mg/m3, μ = 2.765 mm−1, F(000) = 1276, R = 0.0297, and wR = 0.0638 for 18416 observed reflections with I ≥ 2σ(I). One remarkable feature of the two complexes is that the protonated [EnH 2 2+ ] cations conjugating to [EuIII(Ttha)] 2 6− and [EuIII(Egta)(H2O)] 2 2− complex anions are reviewed, respectively, which open the path for the EuIII complexes conjugating with other various biomolecules.