title: Fluorescent and electrochemical sensing of polyphosphate nucleotides by ferrocene functionalised with two Zn(II)(TACN)(pyrene) complexes.
abstract: The [Fc-bis{Zn(II)(TACN)(Py)}] complex, comprising two Zn(II)(TACN) ligands (Fc=ferrocene; Py=pyrene; TACN=1,4,7-triazacyclononane) bearing fluorescent pyrene chromophores linked by an electrochemically active ferrocene molecule has been synthesised in high yield through a multistep procedure. In the absence of the polyphosphate guest molecules, very weak excimer emission was observed, indicating that the two pyrene-bearing Zn(II)(TACN) units are arranged in a trans-like configuration with respect to the ferrocene bridging unit. Binding of a variety of polyphosphate anionic guests (PPi and nucleotides di- and triphosphate) promotes the interaction between pyrene units and results in an enhancement in excimer emission. Investigations of phosphate binding by (31)P NMR spectroscopy, fluorescence and electrochemical techniques confirmed a 1:1 stoichiometry for the binding of PPi and nucleotide polyphosphate anions to the bis(Zn(II)(TACN)) moiety of [Fc-bis{Zn(II)(TACN)(Py)}] and indicated that binding induces a trans to cis configuration rearrangement of the bis(Zn(II)(TACN)) complexes that is responsible for the enhancement of the pyrene excimer emission. Pyrophosphate was concluded to have the strongest affinity to [Fc-bis{Zn(II)(TACN)(Py)}] among the anions tested based on a six-fold fluorescence enhancement and 0.1 V negative shift in the potential of the ferrocene/ferrocenium couple. The binding constant for a variety of polyphosphate anions was determined from the change in the intensity of pyrene excimer emission with polyphosphate concentration, measured at 475 nm in CH(3)CN/Tris-HCl (1:9) buffer solution (10.0 mM, pH 7.4). These measurements confirmed that pyrophosphate binds more strongly (K(b)=(4.45+/-0.41) x 10(6) M(-1)) than the other nucleotide di- and triphosphates (K(b)=1-50 x 10(5) M(-1)) tested.
authors.affiliation: School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Zhanghua
authors.initials: Z
authors.lastname: Zeng
authors.forename: Angel A J
authors.initials: AA
authors.lastname: Torriero
authors.forename: Alan M
authors.initials: AM
authors.lastname: Bond
authors.forename: Leone
authors.initials: L
authors.lastname: Spiccia
mesh_terms: D000465:Algorithms; D005296:Ferrous Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000737:chemistry; D000075163:Metallocenes; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D011721:Pyrenes / Q000138:chemical synthesis* / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000737:chemistry*
chemical_list: D005296:Ferrous Compounds; D006571:Heterocyclic Compounds; D000075163:Metallocenes; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; D011721:Pyrenes; C075712:1,4,7-triazacyclononane; C030984:pyrene; D015032:Zinc; C004998:ferrocene