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Experimental Evidence for a Second Coordination Sphere Water Molecule in the Hydration Structure of YbDTPA – Insights for a Re‐Assessment of the Relaxivity Data of GdDTPA
Author(s) -
Hardcastle Kenneth Irvin,
Botta Mauro,
Fasano Mauro,
Digilio Giuseppe
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200005)2000:5<971::aid-ejic971>3.0.co;2-j
Subject(s) - chemistry , molecule , coordination sphere , carboxylate , crystallography , metal , ligand (biochemistry) , trigonal pyramidal molecular geometry , ion , outer sphere electron transfer , hydrogen bond , stereochemistry , crystal structure , organic chemistry , biochemistry , receptor
The low temperature (–100 °C) X‐ray structure of the complex K 2 [Yb(DTPA)(H 2 O)] has been determined. The metal ion is at the center of a tricapped trigonal prism and is nine‐coordinate, binding to the three nitrogens and five oxygens of the ligand and one water molecule. From the structure obtained, three well‐defined hydration shells can be observed consisting of: i) one coordinated water molecule; ii) several water molecules in the outer coordination sphere of the Yb III ion and iii) one water molecule surprisingly close to the metal center and hydrogen‐bonded to proximate carboxylate groups. A variable‐field and temperature NMRD study of the corresponding Gd complex has been performed and the data interpreted by taking into account the presence of second‐sphere water molecule(s). The results of the analysis are in excellent agreement with the X‐ray structural data.