title: Isoquinoline-based TQEN family as TPEN-derived fluorescent zinc sensors.
abstract: The hexadentate nitrogen ligands 1-isoTQEN ( N,N,N',N'-tetrakis(1-isoquinolylmethyl)ethylenediamine) and 3-isoTQEN ( N,N,N',N'-tetrakis(3-isoquinolylmethyl)ethylenediamine) have been prepared. The structures of these ligands are based on that of TPEN ( N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine). The introduction of a benzene ring into TPEN affords fluorescence ability upon zinc-ion binding. Compared to the quinoline isomer TQEN, isoquinoline derivatives 1-isoTQEN and 3-isoTQEN exhibit a lower-energy shift in the excitation and emission wavelengths and an enhanced fluorescence intensity, probably because of the energy-transfer mechanism between adjacent isoquinoline rings. Importantly, an increase in the Zn (2+)/Cd (2+) discriminating ability and a reduction in the background fluorescence induced by pH were also achieved for isoquinoline derivatives. The zinc-ion-induced fluorescence of these isoTQENs was not quenched by an addition of TPEN, which demonstrates the significantly high zinc-ion binding ability of these isoTQEN ligands.
authors.affiliation: KYOUSEI Science Center and Division of Functional Material Science, 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: Azusa
authors.initials: A
authors.lastname: Yamanaka
authors.forename: Azusa
authors.initials: A
authors.lastname: Yamashita
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Yano
mesh_terms: D018360:Crystallography, X-Ray; D005029:Ethylenediamines / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000138:chemical synthesis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007546:Isoquinolines / Q000737:chemistry*; D008024:Ligands; D011804:Quinolines / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D015032:Zinc / Q000737:chemistry*
chemical_list: D005029:Ethylenediamines; D005456:Fluorescent Dyes; D007546:Isoquinolines; D008024:Ligands; C531591:N,N,N',N'-tetrakis(1-isoquinolylmethyl)ethylenediamine; D011804:Quinolines; C037219:quinoline; D015032:Zinc; C039109:isoquinoline; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine