title: Synthesis and characterization of racemic mixture and meso isomers of bis(trans-2-aminocyclohexyl)aminepentaacetic acid and the stabilities of their Gd(III) complexes.
abstract: The synthesis and characterization of two multidentate ligands, the racemic mixture and meso isomers of bis-(trans-2-aminocyclohexyl)aminepentaacetic acid, are described. Equilibrium constants for their Gd(III) complexes were determined by direct potentiometry. The formation constants (KML = [ML]/[M][L]) of Gd(III)-Cycyracemic in 0.10 M KCl at 25.0 degrees C is 10(20.71; that for the meso isomer is 10(20.42). The crystal structure of (1S,2S,1'S,2'S)-bis(trans-2-aminocyclohexyl)amine-N,N,N',N",N"-pentaacetic acid, penta-tert-butyl ester (C42H75N3O10), is reported. This compound crystallizes in the triclinic system with space group P1 with cell parameters a = 10.805(2) A, b = 11.382(2) A, c = 20.999(4) A, alpha = 91.41(3) degrees, beta = 98.23(3) degrees, gamma = 113.88(3) degrees, V = 2327.8(8) A3, Z = 2, Dx = 1.116 g mL-1. The results are compared to the crystal structures of the gadolinium complexes and the predictions derived from molecular mechanics.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77842-3012, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Sun
authors.forename: A E
authors.initials: AE
authors.lastname: Martell
authors.forename: J H
authors.initials: JH
authors.lastname: Reibenspies
authors.forename: D E
authors.initials: DE
authors.lastname: Reichert
authors.forename: M J
authors.initials: MJ
authors.lastname: Welch
mesh_terms: D000465:Algorithms; D018360:Crystallography, X-Ray; D019786:Gadolinium DTPA / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D019786:Gadolinium DTPA