title: Quinoline-based fluorescent zinc sensors with enhanced fluorescence intensity, Zn/Cd selectivity and metal binding affinity by conformational restriction.
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.
authors.affiliation: KYOUSEI Science Center, Nara Women's University, Nara 630-8506, Japan. mikata@cc.nara-wu.ac.jp
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mikata
authors.forename: Yumi
authors.initials: Y
authors.lastname: Sato
authors.forename: Saaya
authors.initials: S
authors.lastname: Takeuchi
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Kuroda
authors.forename: Hideo
authors.initials: H
authors.lastname: Konno
authors.forename: Satoshi
authors.initials: S
authors.lastname: Iwatsuki
mesh_terms: D002104:Cadmium / Q000032:analysis*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011804:Quinolines / Q000138:chemical synthesis / Q000737:chemistry*; D015032:Zinc / Q000032:analysis*
chemical_list: D005456:Fluorescent Dyes; D009942:Organometallic Compounds; D011804:Quinolines; D002104:Cadmium; C037219:quinoline; D015032:Zinc