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Titolo:
CHARACTERIZATION OF LANTHANIDE(III) DOTP COMPLEXES - THERMODYNAMICS, PROTONATION, AND COORDINATION TO ALKALI-METAL IONS
Autore:
SHERRY AD; REN J; HUSKENS J; BRUCHER E; TOTH E; GERALDES CFCG; CASTRO MMCA; CACHERIS WP;
Indirizzi:
UNIV TEXAS,DEPT CHEM,POB 830688 RICHARDSON TX 75083 UNIV TEXAS,SW MED CTR,MARY NELL & RALPH B ROGERS MAGNET RESONANCE CTR,DEPT RADIOL DALLAS TX 75235 LAJOS KOSSUTH UNIV,DEPT INORGAN & ANALYT CHEM H-4010 DEBRECEN HUNGARY UNIV COIMBRA,FAC SCI & TECHNOL,DEPT BIOCHEM P-3049 COIMBRA PORTUGAL MATTSON JACK GRP ST LOUIS MO 63146
Titolo Testata:
Inorganic chemistry
fascicolo: 16, volume: 35, anno: 1996,
pagine: 4604 - 4612
SICI:
0020-1669(1996)35:16<4604:COLDC->2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
NA-23 SHIFT-REAGENT; PERFUSED RAT-HEART; INTRACELLULAR SODIUM; CONTRAST AGENTS; 10-TETRAAZACYCLODODECANE-N,N',N'',N'''-TETRAACETIC ACID; STABILITY-CONSTANTS; AQUEOUS-SOLUTION; CELLULAR-ENERGY; IN-VIVO; NMR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
41
Recensione:
Indirizzi per estratti:
Citazione:
A.D. Sherry et al., "CHARACTERIZATION OF LANTHANIDE(III) DOTP COMPLEXES - THERMODYNAMICS, PROTONATION, AND COORDINATION TO ALKALI-METAL IONS", Inorganic chemistry, 35(16), 1996, pp. 4604-4612

Abstract

Several solution properties of complexes formed between the trivalentlanthanide ions (Ln(III)) and the macrocyclic ligand DOTP8-, including stability constants, protonation equilibria, and interactions of theLnDOTP(5-) complexes with alkali metal ions, have been examined by spectrophotometry, potentiometry, osmometry, and H-1, P-31, and Na-23 NMR spectroscopy. Spectrophotometric competition experiments between DOTP and arsenate III for complexation with the Ln(III) ions at pH 4 indicate that the thermodynamic stability constants (log K-ML) Of LnDOTP(5-) range from 27.6 to 29.6 from La-III to Lu-III. The value for LaDOTP5- obtained by colorimetry (27.6) was supported by a competition experiment between DOTP and EDTA monitored by H-1 NMR (27.1) and by a potentiometric competition titration between DTPA and DOTP (27.4). Potentiometric titrations of several LnDOTP(5-) complexes indicated that four protonation steps occur between pH 10 and 2; the protonation constantsdetermined by potentiometry were consistent with P-31 Shift titrations of the LnDOTP(5-) complexes. Dissection of the P-31 Shifts of the heavy LnDOTP(5-) complexes (To --> Tm) into contact and pseudocontact contributions showed that the latter dominated at all pH values. The smaller P-31 shifts observed at lower pH for TmDOTP5- were partially due to relaxation of the chelate structure which occurred upon protonation. The P-31 shifts Of Other LnDOTP(5-) complexes (Ln = Pr, Nd, Eu) showed a different pH-dependent behavior, with a change in chemical shift direction occurring after two protonation steps. This behavior was traced to a pH-dependent alteration of the contact shift at the phosphorus nuclei as these complexes were protonated. Na-23 NMR studies of the interactions' of TmDOTP5- with alkali and ammonium cations showed thatEt(4)N(+) and Me(4)N(+) did not compete effectively with Na+ for-the binding sites on TmDOTP5-, while K+ and NH4+ competed more effectivelyand Cs+ and Li+ less effectively. A Na-23 shift of more than 400 ppm was observed at low Na+/TmDOTP5- ratios and high pH, indicating that Na+ was bound near the 4-fold symmetry axis of TmDOTP5- under these conditions. Osmolality measurements of chelate samples containing variousamounts of Na+ indicated that at high Na+/TmDOTP5- ratios at least three Na+ ions were bound to TmDOTP5-. These ions showed a significantlysmaller Na-23-bound shift, indicating they must bind to the chelate at sites further away from the 4-fold symmetry axis. Fully bound Na-23 shifts and relaxation rate enhancements and binding constants for all NaxHyTmDOTP species were obtained by fitting the observed Na-23 shift and relaxation data and the osmometric data, using a spreadsheet approach. This model successfully explained the Na-23 shift and osmolality observed for the commercial reagent Na4HTmDOTP . 3NaOAc (at 80 mM at pH 7.4).

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Documento generato il 28/03/20 alle ore 23:16:53