{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,17]],"date-time":"2025-12-17T08:17:41Z","timestamp":1765959461997,"version":"build-2065373602"},"reference-count":86,"publisher":"Wiley","issue":"35","license":[{"start":{"date-parts":[[2007,10,19]],"date-time":"2007-10-19T00:00:00Z","timestamp":1192752000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["chemistry-europe.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Eur J Inorg Chem"],"published-print":{"date-parts":[[2007,12]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The synthesis and characterization of a new metal chelator, 4\u2010(<jats:italic>S<\/jats:italic>)\u2010hydroxymethyl\u20103,6,10\u2010tri(carboxymethyl)\u20103,6,10\u2010triazadodecanedioic acid (H<jats:sub>5<\/jats:sub>EPTPACH<jats:sub>2<\/jats:sub>OH), is reported. Protonation constants for the ligand H<jats:sub>5<\/jats:sub>EPTPACH<jats:sub>2<\/jats:sub>OH and for the previously reported H<jats:sub>5<\/jats:sub>EPTPAC16 have been determined by potentiometry, which reveals that both ligands display slightly higher protonation constants relative to that of the ligand DTPA<jats:sup>5\u2013<\/jats:sup>. The stability constant for the [Gd(EPTPACH<jats:sub>2<\/jats:sub>OH)(H<jats:sub>2<\/jats:sub>O)]<jats:sup>2\u2013<\/jats:sup> complex has also been determined by potentiometry. The obtained value (log <jats:italic>K<\/jats:italic><jats:sub>GdL<\/jats:sub> = 16.7) is two orders of magnitude lower than that for the [Gd(EPTPA)(H<jats:sub>2<\/jats:sub>O)]<jats:sup>2\u2013<\/jats:sup> complex, which indicates the destabilizing effect of the pendant hydroxymethyl group at the EPTPA backbone. The microscopic protonation scheme has been deduced from the pH dependence of the <jats:sup>1<\/jats:sup>H NMR spectra of both H<jats:sub>5<\/jats:sub>EPTPACH<jats:sub>2<\/jats:sub>OH and H<jats:sub>5<\/jats:sub>EPTPAC16 ligands. The first two protonations occur exclusively at the backbone nitrogen atoms \u2013 the first protonation occurs preferentially at the more basic central nitrogen atom. The second proton distributes preferentially between the two terminal nitrogen atoms with the favoring of the trimethylene nitrogen atom over the ethylene nitrogen atom. The Ln<jats:sup>III<\/jats:sup> complexes of the ligand H<jats:sub>5<\/jats:sub>EPTPACH<jats:sub>2<\/jats:sub>OH have been prepared and their solution dynamics studied by <jats:sup>1<\/jats:sup>H NMR spectroscopy. Two sets of resonances of very different intensities from two isomeric complexes have been observed. Relaxometric investigations (<jats:sup>17<\/jats:sup>O NMR and <jats:sup>1<\/jats:sup>H NMRD) demonstrate that the [Gd(EPTPACH<jats:sub>2<\/jats:sub>OH)(H<jats:sub>2<\/jats:sub>O)]<jats:sup>2\u2013<\/jats:sup> complex displays an accelerated water\u2010exchange rate (<jats:italic>k<\/jats:italic><jats:sub>ex<\/jats:sub> = 87.6\u2009\u00d7\u200910<jats:sup>6<\/jats:sup> s<jats:sup>\u20131<\/jats:sup>) that is close to the theoretically derived optimal value. However, the kinetic stability of this complex in phosphate\u2010buffered solutions towards Zn<jats:sup>2+<\/jats:sup> transmetallation is quite low, but higher than that of the corresponding methyl derivative.(\u00a9 Wiley\u2010VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)<\/jats:p>","DOI":"10.1002\/ejic.200700435","type":"journal-article","created":{"date-parts":[[2007,10,19]],"date-time":"2007-10-19T05:46:37Z","timestamp":1192772797000},"page":"5489-5499","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["H<sub>5<\/sub>EPTPACH<sub>2<\/sub>OH: Synthesis, Relaxometric Characterization and <sup>1<\/sup>H NMR Spectroscopic Studies on the Solution Dynamics of Its Ln<sup>III<\/sup> Complexes"],"prefix":"10.1002","volume":"2007","author":[{"given":"Susana","family":"Torres","sequence":"first","affiliation":[]},{"given":"Jos\u00e9 A.","family":"Martins","sequence":"additional","affiliation":[]},{"given":"Jo\u00e3o P.","family":"Andr\u00e9","sequence":"additional","affiliation":[]},{"given":"Giovannia A.","family":"Pereira","sequence":"additional","affiliation":[]},{"given":"Robert","family":"Kiraly","sequence":"additional","affiliation":[]},{"given":"Ern\u00f6","family":"Br\u00fccher","sequence":"additional","affiliation":[]},{"given":"Lothar","family":"Helm","sequence":"additional","affiliation":[]},{"given":"\u00c9va","family":"T\u00f3th","sequence":"additional","affiliation":[]},{"given":"Carlos F. 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