Tetrahydroindazolone substituted 2-aminobenzamides as fluorescent probes: switching metal ion selectivity from zinc to cadmium by interchanging the amino and carbamoyl groups on the fluorophore.
Three fluorescent probes CdABA', CdABA and ZnABA', which are structural isomers of ZnABA, have been designed with N,N-bis(2-pyridylmethyl) ethylenediamine (BPEA) as chelator and 2-aminobenzamide as fluorophore. These probes can be divided into two groups: CdABA, CdABA' for Cd(2+) and ZnABA, ZnABA' for Zn(2+). Although there is little difference in their chemical structures, the two groups of probes exhibit totally different fluorescence properties for preference of Zn(2+) or Cd(2+). In the group of Zn(2+) probes, ZnABA/ZnABA' distinguish Zn(2+) from Cd(2+) with F(Zn)(2+)-F(Cd)(2+) = 1.87-2.00. Upon interchanging the BPEA and carbamoyl groups on the aromatic ring of the fluorophore, the structures of ZnABA/ZnABA' are converted into CdABA/CdABA'. Interestingly, the metal ions selectivity of CdABA/CdABA' was switched to discriminate Cd(2+) from Zn(2+) with F(Cd)(2+)-F(Zn)(2+) = 2.27-2.36, indicating that a small structural modification could lead to a remarkable change of the metal ion selectivity. (1)H NMR titration and ESI mass experiments demonstrated that these fluorescent probers exhibited different coordination modes for Zn(2+) and Cd(2+). With CdABA' as an example, generally, upon addition of Cd(2+), the fluorescence response possesses PET pathway to display no obvious shift of maximum λ(em) in the absence or presence of Cd(2+). However, an ICT pathway could be employed after adding Zn(2+) into the CdABA' solution, resulting in a distinct red-shift of maximal λ(em).
Department of Chemistry, Beijing Normal University, Beijing 100875, China.
Jia
J
Jia
Qin-Chao
QC
Xu
Ri-chen
RC
Li
Xi
X
Tang
Ying-Fang
YF
He
Meng-Yu
MY
Zhang
Yuan
Y
Zhang
Guo-Wen
GW
Xing
D002104:Cadmium / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005029:Ethylenediamines / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D007191:Indazoles / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000737:chemistry*; D062367:ortho-Aminobenzoates / Q000737:chemistry*
D002614:Chelating Agents; D005029:Ethylenediamines; D005456:Fluorescent Dyes; D007191:Indazoles; D062367:ortho-Aminobenzoates; D002104:Cadmium; D015032:Zinc; C000219:anthranilamide