Fluorescent aza-cyclophanes derived from diethylenetriaminepentaacetic acid (DTPA), and their complexation with Gd(III)

Yedith Soberanes, Ana Gabriela Arvízu-Santamaría, Lorena MacHi, Rosa Elena Navarro*, Motomichi Inoue

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Chelating aza-cyclophanes were synthesized by reactions of diethylenetriaminepentaacetic acid (or DTPA) dianhydride with aromatic diamines, 4,4′-diaminobibenzyl (DAB) and 4,4′-bis(1,1′-biphenyl-4, 4′-diyldioxy)dianiline (BPA). The former amine gave a 2:2-cyclization product bearing six -CH 2CO 2H arms, 2,12,29,39-tetraoxo-4, 7,10,31,34,37-hexakis(carboxymethylene)-1,4,7,10,13,28,31,34,37,40-decaaza-[13. 2.13.2]ethylenparacyclophane, abbreviated as cy(bisdtpadab)H 6, whereas BPA yielded a 1:1-cyclization product carrying three -CH 2CO 2H arms, 2,12-dioxo-4,7,10-trakis(carboxymethylene)-1, 4,7,10,13-pentaaza-20,33-dioxa[13.0.1]paracyclophane, abbreviated as cy(dtpabpa)H 3. Their protonation and complexation with Gd(III) were studied by fluorescence spectra, 1H NMR and potentiometry. The macrocyclic framework of cy(dtpabpa)H 3 has a high rigidity; as a consequence, this ligand is incapable of forming a complex with Gd(III). In contrast, cy(bisdtpadab)H 6, which is moderately rigid, forms a binuclear Gd(III) complex, as confirmed by a sensitive quenching of the fluorescence upon complexation. On the basis of the pH dependence of the fluorescence spectra, the logarithmic overall formation constants were determined as log β M2L = 28.3, log β M2LH = 31.9, log β M2LH-1 = 21.0, logβ M2LH-2 = 9.8. For the chelating cyclophanes, the rigidity is one of major controlling factors for the stability of their complexes. The sharp change in the fluorescence intensity upon complexation with Gd 3+ ion suggests that the chelating cyclophane works potentially as fluorescent probes toward specific metal ions.

Original languageEnglish
Pages (from-to)130-136
Number of pages7
JournalPolyhedron
Volume35
Issue number1
DOIs
StatePublished - 16 Mar 2012

Bibliographical note

Funding Information:
This work was supported in part by the Consejo Nacional de Ciencia y Tecnología de México (CONACYT, Grant No. P82933 and 104423 ) and the Secretaría de Educación Pública, México (SEP, project PIFI-FO 2008–2009). Y.S. thanks CONACYT for graduate scholarship.

Keywords

  • Binuclear complexes
  • DTPA
  • Fluorescence
  • Formation constants
  • Gd(III) complexes
  • Macrocycles

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