Solution Dynamics and Stability of Lanthanide(III) (S)-2-(p-Nitrobenzyl)DOTA Complexes
Addition of a benzyl substituent to the macrocyclic ring of DOTA has a substantial impact on the conformational ring flipping motion of the macrocycle in the resulting LnDOTA complexes. The p-NO2-benzyl substituent in the Ln(p-NO2-Bn-DOTA)- complexes lies in an equatorial position and effectively “locks” the conformation of the ring into the δδδδ configuration. The presence of the p-NO2-benzyl group also increases the population of the square antiprismatic (SAP) coordination isomer for all Ln(p-NO2-Bn-DOTA)- complexes relative to that seen for the respective LnDOTA- complexes. Despite this increase in SAP isomer population, the rate of water exchange in these complexes remains comparatively fast. The kinetic and thermodynamic stabilities of the Ln(p-NO2-Bn-DOTA)- complexes are also slightly lower than the corresponding LnDOTA- complexes but appear to be sufficiently high for in vivo use.
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Woods, M., Kovacs, Z., Kiraly, R., Brücher, E., Zhang, S., & Sherry, A. D. (2004). Solution dynamics and stability of lanthanide (III)(S)-2-(p-nitrobenzyl) DOTA complexes. Inorganic chemistry, 43(9), 2845-2851.