An X-ray structural study of organic ligands of the complexone type. V. The first example in complexones of an intramolecular hydrogen bond N?H...N in trans-cyclohexane-1,2-diamine-N,N,N?,N?-tetra-acetic acid monohydrate

Synthesis and Characterization of Racemic Mixture and Meso Isomers of Bis(trans-2-aminocyclohexyl)aminepentaacetic Acid and the Stabilities of Their Gd(III) Complexes

“…Figure illustrates the structure of one of the isomers of the racemic mixture: (1S,2S,1‘S,2‘S)-bis( trans- 2-aminocyclohexyl)amine− N , N,N ‘, N ‘ ‘, N ‘ ‘-pentaacetic acid, penta- tert -butyl ester. The average N−C bond distance is 1.47 Å and compares well with that of CDTA (1.462 Å) . The C−N−C bond angles of the two peripheral nitrogen are almost identical to those of DTPA, and the difference in the angles of the middle nitrogen is probably due to the formation of a hydrogen bond in DTPA …”

“…The cyclohexane rings of the molecules have the chair conformation with standard values of both valence angles and the C−C distances at the carbon atoms. The average value of the C−C−C angle is 110.9(3)°, comparable with that of CDTA, 110.5(3)°, and the average of C−C distances is 1.530(5) Å, very close to that of CDTA, 1.523(5) Å . The values of the torsional angles are also characteristic of cyclohexane.…”