title: Synthesis, characterization and metal ion-sensing properties of two Schiff base derivatives.
abstract: Two new Schiff base derivatives {2,2'-diphenyl-N,N'-bis(2-pyridylmethylene)biphenyl-4,4'-diamine} (1) and {2,2'-diphenyl-N,N'-bis(salicylidene)biphenyl-4,4'-diamine} (2) were synthesized and characterized by means of elemental analysis, (1)H NMR, FT-IR, and standard spectroscopy techniques. The molecular structure of 2 has been determined by X-ray single crystal analysis. The analyses of fluorescence properties of the compounds revealed that 1 and 2 are both poorly fluorescent and display sensitive fluorescence responses to a panel of 24 monovalent, divalent, and trivalent metal ions in CH(3)CN-DMSO (9:1, v/v). Results with imine 1 showed that Fe(3+), Cu(2+), Zn(2+), Cd(2+), Mn(2+), Zr(4+), Hg(2+), Cr(2+), Pb(2+), Sn(2+), Bi(2+), Al(3+), Ce(3+), La(3+), Sm(3+), Gd(3+), Nd(3+), Eu(3+) and Dy(3+) yields red shifts in emission and increases in intensity. And the greatest spectral changes for imine 2 include enhancements in emission intensity coupled with red shifts (Zr(4+), Sn(2+), Al(3+) and Zn(2+)) and strong quenching (Fe(3+)). The fluorescence enhancement mechanism of 1 and 2 for metal ions is based on: (i) CN isomerization; (ii) chelation-enhanced fluorescence (CHEF) effect; and (iii) excited-state intra/intermolecular proton transfer (ESPT).
authors.affiliation: Applied Chemistry Department, School of Material Science & Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, PR China.
authors.forename: Huihua
authors.initials: H
authors.lastname: Xu
authors.forename: Xian
authors.initials: X
authors.lastname: Tao
authors.forename: Yueqin
authors.initials: Y
authors.lastname: Li
authors.forename: Yingzhong
authors.initials: Y
authors.lastname: Shen
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Wei
mesh_terms: D002412:Cations / Q000032:analysis; D003959:Diamines / Q000138:chemical synthesis / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D008670:Metals / Q000032:analysis*; D008958:Models, Molecular; D012545:Schiff Bases / Q000138:chemical synthesis / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002412:Cations; D003959:Diamines; D005456:Fluorescent Dyes; D008670:Metals; D012545:Schiff Bases