Orientational disorder in Λ‐cobalt(III) sepulchrate trinitrate

The crystal structure of Λ‐(1,3,6,8,10,13,16,19‐octaazabicyclo[6.6.6]eicosane)cobalt(III) trinitrate, [Co(C₁₂H₃₀N₈)](NO₃)₃, consists of a sepulchrate moiety that serves as a macrobicyclic nitrogen cage for the Co³⁺ cation, which is six‐coordinated by N atoms, and three nitrate anions. The Co–sepulchrate group lies on a threefold axis (site symmetry 32), as do two symmetry‐related and ordered nitrate groups (site symmetry 3), with which it is connected via N—H...O hydrogen bonds [Co—N = 5.1452 (12) Å]. The third nitrate group is disordered as a result of symmetry requirements around the origin (site symmetry 32), and is further away from the Co–sepulchrate cage [Co—N = 6.3160 (8) Å]. The structure is described by applying orientational disorder over six equivalent orientations for the disordered nitrate group, which is considered as an ideal planar molecule of regular trigonal geometry with its molecular plane rotated out of the ab plane and the molecular centre of gravity slightly shifted away from the origin. This new model for disorder clearly improves a previous crystal structure determination.     

Liquid chromatography of lanthanide chelates of 1-(p-nitrophenyl)ethylenediamine-N,N,N',N' -tetra-acetic acid

Preparation of the chelating agent, 1-(p-nitrophenyl)ethylenediamine-N,N,N',N'-tetra-acetic acid (p-nitrophenylEDTA), is described in detail. Separation of p-nitrophenylEDTA chelates of ytterbium(III), erbium(III), dysprosium(III) and europium(III) has been achieved by reversed-phase ion-pair liquid chromatography. With spectrophotometric detection at 254 nm, linear responses over about four orders of magnitude were achieved with detection limits (S/N = 2) of about 0.5 pmole.     

Radiolysis of cobalt(III)-1,2 bis(beta-aminoethoxy)ethane N,N,N',N' sodium sulfonate triacetic acid chelate

Chelation studies of cobalt(III) with 1,2 bis(beta-aminoethoxy)ethane N,N,N',N' sodium sulfonate triacetic acid (ASTA) were performed. The results showed the effectiveness of ASTA as a chelating agent by using: molar ratio, continuous variation and slope ratio methods. Stable complex 1∶1 was formed at pH from 6.0 to 10.5. Solutions of Co-ASTA chelate of different molar ratios at pH 6.5 and 8.0 were irradiated by different gamma-radiation doses. The results showed a linear decrease of absorbance with gamma-radiation dose which can be utilized as a dosimeter for low dose rate measurement in the range studied. A proposed radiolytic mechanism is discussed. The degradation of the ASTA ligand has been related to hydroxyl radical attack.