Polyvalent Scaffolds. Counting the Number of Seats Available for Eosin Guest Molecules in Viologen-Based Host Dendrimers

Filippo Marchioni, Margherita Venturi, Alberto Credi, Vincenzo Balzani*, Martin Belohradsky, Arkadij M. Elizarov, Hsian Rong Tseng, J. Fraser Stoddart

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Scopus citations

Abstract

We have prepared and investigated two dendrimers based on a 1,3,5-trisubstituted benzenoid-type core, containing 9 and 21 viologen units in their branches, respectively, and terminated with tetraarylmethane derivatives. We have shown that, in dichloromethane solution, such highly charged cationic species give rise to strong host-guest complexes with the dianionic form of the red dye eosin. Upon complexation, the absorption spectrum of eosin becomes broader and is slightly displaced toward lower energies, whereas the strong fluorescence of eosin is completely quenched. Titration experiments based on fluorescence measurements have shown that each viologen unit in the dendrimers becomes associated with an eosin molecule, so that the number of positions ("seats") available for the guest molecules in the hosting dendrimer is clearly established, e.g., 21 for the larger of the two dendrimers. The host-guest interaction can be destroyed by addition of chloride ions, a procedure which permits eosin to escape from the dendrimer's interior in a controlled way and to regain its intense fluorescence. When chloride anions are precipitated out by addition of silver cations, eosin molecules re-enter the dendrimer's interior and their fluorescence again disappears.

Original languageEnglish (US)
Pages (from-to)568-573
Number of pages6
JournalJournal of the American Chemical Society
Volume126
Issue number2
DOIs
StatePublished - Jan 21 2004

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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