Self-assembled metalla-bowls for selective sensing of multi-carboxylate anions

Dalton Trans. 2012 Jan 28;41(4):1195-201. doi: 10.1039/c1dt11612f. Epub 2011 Nov 25.

Abstract

Two new tetranuclear cationic metalla-bowls 4 and 5 were self-assembled from a bis-pyridine amide ligand (H(2)L) (1) and arene-ruthenium acceptors, [(Ru(2)(μ-η(4)-C(2)O(4))(η(6)-p-cymene)(2)](O(3)SCF(3))(2) (2) and [Ru(2)(dhnd)(η(6)-p-cymene)(2)](O(3)SCF(3))(2) (dhnd = 6,11-dihydroxy-5,12-naphthacenedionato) (3), respectively. The metalla-bowls were characterized by multinuclear NMR, ESI-MS, UV-Vis spectroscopy, and single crystal X-ray diffraction study of 4. The crystal structure of 4 reveals unambiguous proof for the molecular shape of the metalla-bowl and the encapsulation of one triflate anion in the cavity through hydrogen bonding. The metalla-bowl 5 has been evaluated for anion binding studies by use of amide ligand as a hydrogen bond donor and arene-Ru acceptor as a signalling unit. UV-Vis titration studies showed that 5 selectively binds with multi-carboxylate anions such as oxalate, tartrate and citrate in a 1 : 1 fashion with high binding constants of 4.0-5.5 × 10(4) M(-1). Furthermore, the addition of multi-carboxylate anions into a solution of 5 gave rise to a large enhancement of fluorescence intensity attributable to the blocking of a photo-induced electron transfer process from the arene-ruthenium moiety to the amidic donor in 5. However, the fluorescence intensity almost remains unchanged upon addition of other anions including F(-), Cl(-), PF(6)(-), MeCOO(-), NO(3)(-) and PhCOO(-), as identically seen in the UV-Vis titration experiments, pointing to the high selectivity of 5 for the sensing of multi-carboxylate anions.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Absorption
  • Amides / chemistry
  • Carboxylic Acids / analysis*
  • Carboxylic Acids / chemistry*
  • Models, Molecular
  • Molecular Conformation
  • Organometallic Compounds / chemical synthesis
  • Organometallic Compounds / chemistry*
  • Pyridines / chemistry
  • Ruthenium / chemistry

Substances

  • Amides
  • Carboxylic Acids
  • Organometallic Compounds
  • Pyridines
  • Ruthenium
  • pyridine