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001-es BibID:BIBFORM018844
Első szerző:Aime, Silvio
Cím:Properties, Solution State Behavior, and Crystal Structures of Chelates of DOTMA / Silvio Aime, Mauro Botta, Zoltán Garda, Benjamin E. Kucera, Gyula Tircso, Victor G. Young, Mark Woods
Dátum:2011
ISSN:0020-1669
Megjegyzések:The chemistry of polyamino carboxylates and their use as ligands for Ln3+ ions is of considerable interest from the point of view of the development of new imaging agents. Of particular interest is the chemistry of the macrocyclic ligand 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and its derivatives. Herein we report that the tetramethylated DOTA derivative, DOTMA, possess several properties that, from an imaging agent development point of view, are more advantageous than those of the parent DOTA. In particular, the Ln3+ chelates of DOTMA exhibit a marked preference for the monocapped twisted square antiprismatic coordination isomer which imparts more rapid water exchange kinetics on the chelates; ?M298 was determined to be 85 ns for GdDOTMA. Differential analysis of the 17O R2? temperature profiles of both GdDOTA and GdDOTMA afforded the ?M298 values for the square (SAP) and twisted square antiprismatic (TSAP) isomers of each chelate that were almost identical: 365 ns (SAP) and 52 ns (TSAP). The origin of this accelerated water exchange in the TSAP isomer appears to be the slightly longer Gd?OH2 bond distance (2.50 Å) that is observed in the crystal structure of GdDOTMA which crystallizes in the P2 space group as a TSAP isomer. The Ln3+ chelates of DOTMA also exhibit high thermodynamic stabilities ranging from log KML = 20.5 for CeDOTMA, 23.5 for EuDOTMA and YbDOTMA comparable to, but a shade lower than, those of DOTA.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Inorganic Chemistry. - 50 : 17 (2011), p. 7955-7965. -
További szerzők:Botta, Mauro Garda Zoltán (1989-) (vegyész) Kucera, Benjamin E. Tircsó Gyula (1977-) (vegyész, kémia tanár) Young, Victor G. Woods, Mark
Internet cím:DOI
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001-es BibID:BIBFORM018841
Első szerző:Tircsó Gyula (vegyész, kémia tanár)
Cím:Analysis of the Conformational Behavior and Stability of the SAP and TSAP Isomers of Lanthanide(III) NB-DOTA-Type Chelates / Gyula Tircso, Benjamin C. Webber, Benjamin E. Kucera, Victor G. Young, Mark Woods
Dátum:2011
ISSN:0020-1669
Megjegyzések:Controlling the water exchange kinetics of macrocyclic Gd3+ chelates, a key parameter in the design of improved magnetic resonance imaging (MRI) contrast media, may be facilitated by selecting the coordination geometry of the chelate. The water exchange kinetics of the mono- capped twisted square antiprism (TSAP) being much closer to optimal than those of the mono capped square antiprism (SAP) render the TSAP isomer more desirable for high relaxivity applications. Two systems have been developed that allow for selection of the TSAP coordination geometry in 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-type Gd3+ chelates, both based upon the macrocycle nitrobenzyl cyclen. In this paper we report investigations into the stability and formation of these chelates. Particular focus is given to the production of two regioisomeric chelates during the chelation reaction. These regioisomers are distinguished by having the nitrobenzyl substituent either on a corner or on the side of the macrocyclic ring. The origin of these two regioisomers appears to stem from a conformation of the ligand in solution in which it is hypothesized that pendant arms lie both above and below the plane of the macrocycle. The conformational changes that then result during the formation of the intermediate H2GdL+ chelate give rise to differing positions of the nitrobenzyl substituent depending upon from which face of the macrocycle the Ln3+ approaches the ligand.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Inorganic Chemistry. - 50 : 17 (2011), p. 7966-7979. -
További szerzők:Webber, Benjamin C. Kucera, Benjamin E. Young, Victor G. Woods, Mark
Internet cím:DOI
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