Syntheses, structural determination and binding studies of nine-coordinate mononuclear (EnH 2 ) 1.5 [Er III (Ttha)] · 3H 2 O and (EnH 2 )[Er III (Egta)(H 2 O)] 2 · 6H 2 O

In this work, the title complexes, (EnH 2 ) 1.5 [Er III (Ttha)] · 3H 2 O ( I ) and (EnH 2 )[Er III (Egta)(H 2 O)] 2 · 6H 2 O ( II ), where En = ethylenediamine, H 6 Ttha = triethylenetetramine- N,N,N′,N″,N″’,N″′ -hexaacetic acid, H 4 Egta = ethyleneglycol-bis-(2-aminoethylether)- N,N,N′,N′ -tetraacetic acid, have been successfully synthesized. Their structures have been characterized by IR spectroscopy and single-crystal X-ray diffraction techniques. The X-ray diffraction reveals that I is nine-coordinated and crystallizes in the monoclinic crystal space group P 2/ n with cell dimensions a = 17.6058(16), b = 9.6249(9), c = 20.560(2) Å, β = 109.7440(10)°, and V = 3279.1(5) Å 3 . Compound II is also nine-coordinated and crystallizes in the monoclinic crystal space group P 2 1 / n with the cell dimensions a = 12.938(6), b = 12.651(5), c = 14.943(6) Å, β = 105.441(5)°, and V = 2357.5(17) Å 3 . In I , each EnH 2 2+ cation connects three adjacent [Er III (Egta)(H 2 O)] − complex anions through hydrogen bonds, while in I , there are two types of EnH 2 2+ anions. One is highly symmetrical, forming hydrogen bonds with two neighboring [Er III (Ttha)] 3− complex anions. The other anion connects three adjacent [Er III (Ttha)] 3− complex anions through hydrogen bonds. These hydrogen bonds lead to the formation of 2D ladder-like layer structure.