Determination of the Prototropic Exchange Rate at the Water Molecule Coordinated to an Anionic Paramagnetic GdIII Chelate

✍ Scribed by Silvio Aime; Simonetta Geninatti Crich; Eliana Gianolio; Enzo Terreno; Andrea Beltrami; Fulvio Uggeri

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 519 KB
• Volume: 1998
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/(sici)1099-0682(199809)1998:9<1283::aid-ejic1283>3.0.co;2-b

✦ Synopsis

A thorough investigation of the proton and oxygen-17 protons. This situation has been exploited to assess the prototropic exchange rate from the coordinated water to the relaxation rates of water nuclei has been carried out for a solution containing an amphiphilic, paramagnetic Gd III bulk, which is base-catalyzed. In fact, under these experimental conditions, at basic pH, the proton transfer is chelate of potential interest as a contrast agent for MRI. It has been found that at pH = 7, 298 K and 20 MHz (proton faster than the exchange of the whole water molecule, and it becomes the factor determining the observed relaxation observation frequency), the contribution to the overall relaxation enhancement from the water molecule in the inner enhancement. The effect is further enhanced at low temperature as a consequence of the concomitant coordination sphere is dominated by the relaxation time ( T H 1M ) of its protons. However, upon formation of a slowly lengthening of either τ R (which causes a reduction of T H 1M ) and/or the exchange lifetime of the coordinated water tumbling adduct with β-cyclodextrin, the observed relaxation enhancement is also affected by the exchange lifetime (τ H M ) molecule. of the coordinated water and by the transfer rate of its