Complexation properties of macrocyclic polyoxadiazadiphosphonates

László Burai, Sándor Jakab, R. Király, István Lázár, Imre Tóth, E. Brücher

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

The macrocycle 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyldimethyleriediphosphonic acid (H4L1), its bis(ethyl ester) (H2L3) and 1,4,10-trioxa-7,13-diazacyclopentadecane-7,13-diyldimethylenediphosphonic acid (H4L5) were prepared. The protonation constants of the macrocycles and the stability constants of their complexes with alkaline-earth-metal ions, lanthanide ions, Zn2+ Cd2+ and Pb2+ were determined by pH-potentiometric titration. The phosphonate (L3)2- forms only unprotonated complexes ML, while (L1)4- and (L5)4- form ML, monoprotonated complexes, M(HL), and diprotonated complexes, M(H2L). The trends in the stability constants through the lanthanide series are similar for all complexes: a weak maximum in log K is observed at around Pr3+, Nd3+ and a minimum at about Tb3+, Ho3+. The chemical shifts of the non-labile protons of L1 indicate that on protonation the first two protons are attached to the two nitrogens, the next two at one of the oxygen atoms of each phosphonate group. The equilibrium data and 1H NMR spectra of the complexes [LaL1]- and [LuL1]- indicate the increasing role of the metal-phosphonate group interaction in the complexation through the lanthanide series from La3+ to Lu3+. Attachment of the strongly co-ordinating phosphonate groups to the 15- and 18-membered ring macrocycles results in cessation of the size-match selectivity.

Original languageEnglish
Pages (from-to)1113-1118
Number of pages6
JournalJournal of the Chemical Society, Dalton Transactions
Issue number6
Publication statusPublished - Mar 21 1996

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Organophosphonates
Complexation
Lanthanoid Series Elements
Protonation
Protons
Alkaline Earth Metals
Acids
Chemical shift
Titration
Metal ions
Esters
Nitrogen
Metals
Nuclear magnetic resonance
Ions
Oxygen
Atoms

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Complexation properties of macrocyclic polyoxadiazadiphosphonates. / Burai, László; Jakab, Sándor; Király, R.; Lázár, István; Tóth, Imre; Brücher, E.

In: Journal of the Chemical Society, Dalton Transactions, No. 6, 21.03.1996, p. 1113-1118.

Research output: Contribution to journalArticle

Burai, László ; Jakab, Sándor ; Király, R. ; Lázár, István ; Tóth, Imre ; Brücher, E. / Complexation properties of macrocyclic polyoxadiazadiphosphonates. In: Journal of the Chemical Society, Dalton Transactions. 1996 ; No. 6. pp. 1113-1118.
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abstract = "The macrocycle 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyldimethyleriediphosphonic acid (H4L1), its bis(ethyl ester) (H2L3) and 1,4,10-trioxa-7,13-diazacyclopentadecane-7,13-diyldimethylenediphosphonic acid (H4L5) were prepared. The protonation constants of the macrocycles and the stability constants of their complexes with alkaline-earth-metal ions, lanthanide ions, Zn2+ Cd2+ and Pb2+ were determined by pH-potentiometric titration. The phosphonate (L3)2- forms only unprotonated complexes ML, while (L1)4- and (L5)4- form ML, monoprotonated complexes, M(HL), and diprotonated complexes, M(H2L). The trends in the stability constants through the lanthanide series are similar for all complexes: a weak maximum in log K is observed at around Pr3+, Nd3+ and a minimum at about Tb3+, Ho3+. The chemical shifts of the non-labile protons of L1 indicate that on protonation the first two protons are attached to the two nitrogens, the next two at one of the oxygen atoms of each phosphonate group. The equilibrium data and 1H NMR spectra of the complexes [LaL1]- and [LuL1]- indicate the increasing role of the metal-phosphonate group interaction in the complexation through the lanthanide series from La3+ to Lu3+. Attachment of the strongly co-ordinating phosphonate groups to the 15- and 18-membered ring macrocycles results in cessation of the size-match selectivity.",
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