Quinoline-based fluorescent zinc sensors with enhanced fluorescence intensity, Zn/Cd selectivity and metal binding affinity by conformational restriction

Dalton Trans. 2013 Jul 14;42(26):9688-98. doi: 10.1039/c3dt50719j. Epub 2013 May 16.

Abstract

Two cyclohexanediamine-based tetrakisquinoline derivatives, N,N,N',N'-tetrakis(2-quinolylmethyl)-trans-1,2-cyclohexanediamine (TQDACH) and N,N,N',N'-tetrakis(1-isoquinolylmethyl)-trans-1,2-cyclohexanediamine (1-isoTQDACH), have been prepared and their zinc-induced fluorescent response was investigated. In DMF-H2O (1 : 1) solution, TQDACH exhibits increase of fluorescence at 455 nm in the presence of 1 eq. of zinc ion (λ(ex) = 317 nm, φ = 0.010). Similarly, 1-isoTQDACH exhibited fluorescence enhancement upon binding with zinc (λ(ex) = 325 nm, λ(em) = 352 and 475 nm, φ = 0.032). The fluorescence intensity ratio induced by cadmium relative to zinc (I(Cd)/I(Zn)) for these 1,2-cyclohexanediamine probes is lower than those for the corresponding ethylenediamine derivatives, TQEN and 1-isoTQEN. Crystal structures of the zinc and cadmium complexes of TQDACH and 1-isoTQDACH reveal the superior metal binding ability of the 1,2-cyclohexanediamine and isoquinoline moieties in comparison to ethylenediamine and quinoline. The conformational restriction afforded by the 1,2-cyclohexanediamine skeleton upon zinc binding leads to enhanced fluorescence intensity and strong metal binding affinity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cadmium / analysis*
  • Fluorescence
  • Fluorescent Dyes / chemical synthesis
  • Fluorescent Dyes / chemistry*
  • Molecular Conformation
  • Organometallic Compounds / chemical synthesis
  • Organometallic Compounds / chemistry*
  • Quinolines / chemical synthesis
  • Quinolines / chemistry*
  • Zinc / analysis*

Substances

  • Fluorescent Dyes
  • Organometallic Compounds
  • Quinolines
  • Cadmium
  • quinoline
  • Zinc