Relaxation of solvent protons by solute Gd3+-chelates, revisited

✍ Scribed by Kenneth E. Kellar; P. Mark Henrichs; Marga Spiller; Seymour H. Koenig

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 641 KB
• Volume: 37
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910370515

✦ Synopsis

Abstract

The magnetic field dependence (NMRD profile) of 1/T~1~, of solvent protons in an aqueous solution of Gd(DTPA)^2−^ was remeasured at 5,15,25,30, and 35°C. The data were reanalyzed with the usual low‐field theory, using recently published values for T~M~, the residence lifetime of the single inner‐coordinated waters of solute Gd(DTPA)^2−^. (These T~M~ values are significantly longer than earlier estimates). Values were obtained for three dynamic parameters: T~R~, the rotational relaxation time of solute ions, and T~SO~ and T~V~, the low‐field relaxation time of the Gd^3+^ magnetic moment and the related correlation time. These Gd(DTPA)^2+^ values, together with recent results for T~M~ for Gd(DTPA‐BMA) — a nonionic structural analog of Gd(DTPA)^2−^ with an unusually long T~M~ — were used to calculate NMRD profiles at 5 and 35°C. These profiles agree very well with new data given here for a solution of Gd(DTPA‐BMA). This reaffirms the importance of knowing the temperaturedependent values of T~M~ a priori in order to obtain unambiguous quantitative theoretical analyses of NMRD profiles of chelates of known structure. Additionally, the theory of inner sphere relaxation is extended to high fields, at which the magnetic energy of a solute moment is greater than its thermal energy.