American Chemical Society
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Formation of Two Diverse Classes of Poly(amino-alkoxide) Chelates and Their Mononuclear and Polynuclear Lanthanide(III) Complexes

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posted on 2003-07-16, 00:00 authored by Marlon K. Thompson, Alan J. Lough, Andrew J. P. White, David J. Williams, Ishenkumba A. Kahwa
Factors that influence aggregation of lanthanide(III) (LnIII) ions to form polynuclear complexes were studied utilizing 1-aziridineethanol as a versatile source of macrocyclic and acyclic chelates. The facile ring-opening cyclo-oligomerization of 1-aziridineethanol leads to the formation of a series of polyaza cyclic oligomers (series A). In the presence of ethylenediamine, a competing N-alkylation reaction occurs to produce a new class of acyclic ligands (series B). The cyclo-oligomerization of four 1-aziridineethanol units is the most favorable process, leading to the formation of the 12-membered cyclen-type macrocycle, H4L1 (1,4,7,10-tetrakis(2-hydroxyethyl)-1,4,7,10-tetraaza-cyclododecane). Ring-opening cyclo-oligomerization of 1-aziridineethanol in the presence of LnIII ions produces self-assembled mononuclear, tetranuclear, and pentanuclear compounds of H4L1. In the presence of ethylenediamine, oligomerization of 1-aziridineethanol results in a dinuclear complex of an acyclic poly(amino-alkoxide) H2L2. The coordinative unsaturation of (i) the alkoxy sites of [HxL1]x-4 (where x < 4) and (ii) LnIII ions in coordination numbers less than nine are critical factors in the formation of the polynuclear LnIII complexes. The identities of mononuclear, dinuclear, tetranuclear, and pentanuclear complexes herein discussed were established by X-ray crystallography.