Search

A commercially available probe (RS) has been reported for instantaneous selective colorimetric detection of Cu(II) and fluorescent detection of Al(III) ions in H2O:DMSO (90:10% v/v) medium. The probe displays a color change from pale yellow (kab 352 nm) to yellowish-green (kab 411 nm) with Cu(II) and a change in emission from green (tex 340nm; tem 522 nm) to bluish-green (tem 489nm) with Al(III) ions. The optical detection of these metal ions by RS is via the formation of tetragonally distorted octahedral RS-Cu(II) and tetrahedral RS-Al(III) complexes as evidenced from the results of UV-Vis, 27Al & ¹H NMR, HRMS, EPR and thermal analysis studies. Job's method indicates that the stoichiometry of both these complexes is 1:1. The probe's corresponding optical changes are particular for Cu(II) and Al(III) ions in the presence of other metal ions. RS displays high selectivity to these ions in a wide pH range. The limits of the detection of Cu(II) and Al(III) are as low as 66nM and 0.83 mM, respectively. Further, RS could be applied as a fluorescent probe for observing Al(III) ions in living HeLa cells by carrying out cell image studies.A commercially available probe (RS) has been reported for instantaneous selective colorimetric detection of Cu(II) and fluorescent detection of Al(III) ions in H2O:DMSO (90:10% v/v) medium. The probe displays a color change from pale yellow (kab 352 nm) to yellowish-green (kab 411 nm) with Cu(II) and a change in emission from green (kex 340nm; kem 522 nm) to bluish-green (kem 489nm) with Al(III) ions. The optical detection of these metal ions by RS is via the formation of tetragonally distorted octahedral RS-Cu(II) and tetrahedral RS-Al(III) complexes as evidenced from the results of UV-Vis, 27Al & 1H NMR, HRMS, EPR and thermal analysis studies. Job's method indicates that the stoichiometry of both these complexes is 1:1. The probe's corresponding optical changes are particular for Cu(II) and Al(III) ions in the presence of other metal ions. RS displays high selectivity to these ions in a wide pH range. The limits of the detection of Cu(II) and Al(III) are as low as 66nM and 0.83 mM, respectively. Further, RS could be applied as a fluorescent probe for observing Al(III) ions in living HeLa cells by carrying out cell image studies. [ABSTRACT FROM AUTHOR]

Three Schiff base based probes exhibit high selectivity and sensitivity CN− and Al(III) ions with striking fluorescent signaling responses in H 2 O-DMSO (1:1, v/v), wherein electron withdrawing nitro substituent polarizes the imine bond to a larger extent resulting in easier addition of CN− to imine C-atom while electron releasing tert -Bu substituent produces opposite effect leading to sluggish addition reaction. • Three Schiff bases exhibit high selectivity and sensitivity CN− and Al(III) ions. • Mechanism of detection of CN− involves deprotonation followed by nucleophilic addition. • Electron withdrawing nitro substituent results in easier addition of CN− to imine C-atom. • Formation of tetrahedral Al(III) complex leads to enhancement in fluorescence. Three Schiff base based probes are designed and synthesized by facile condensation of a commercially available fluorophore 2,6-diformyl-4- tert -butylphenol with 4-nitro-2-aminophenol (KP1), 2-aminophenol (KP2) and 4- tert -butyl-2-aminophenol (KP3) and are characterized using various spectral techniques. The probes exhibit high selectivity and sensitivity CN− and Al(III) ions with striking fluorescent signaling responses in H 2 O-DMSO (1:1, v/v) medium. The mechanism of the probes' detection of CN involves deprotonation of the phenolic OH group(s) followed by nucleophilic addition of CN− onto imine C-atom. The 1H NMR chemical shifts of the OH protons of 2-aminophenol moiety exhibits a linear correlation with the Hammett's substituent constants (σ p), yielding a positive reaction constant (ρ). In KP1 , the electron-withdrawing nitro substituent polarizes the imine bond to a larger extent than in KP2 , resulting in easier addition of CN− to imine C-atom. The electron releasing tert -Bu substituent in KP3 produces the opposite effect leading to a sluggish addition reaction. The separately populated HOMO and LUMO in KP1 and a relatively lower HOMO-LUMO energy gap indicate substantial intramolecular charge transfer (ICT) character, leading to weak fluorescence emission. The large reduction in HOMO-LUMO energy gap, in KP1 , upon addition of cyanide is responsible for the greater enhancement in fluorescence with blue shift upon addition of CN−. Formation of tetrahedral Probe-Al(III) complex prevents the isomerization of imine bond, leading to enhancement in fluorescence and contribution from chelation enhanced fluorescence. As these probes show very low limits of detection of these ions, their practical utility has also been demonstrated. [ABSTRACT FROM AUTHOR]

• The probe displays a rapid fluorescent response for CN− and Al(III). • Enhancement in fluorescence occurs in neat DMSO and H 2 O-DMSO (1:1 v/v) media. • Addition of CN− exhibits enhancement in green fluorescence at 505 nm via deprotonation. • Addition of Al(III) increases bluish-green fluorescence via CHEF mechanism. • The probe was successfully applied to detect these ions in food/pharmaceutical samples. The commercially available fluorophore, 3-hydroxy-2-naphthoic hydrazide (RS2), has rationally been selected for the study, which displays a rapid fluorescent response and high sensitivity for CN− and Al(III) ions in neat DMSO and H 2 O-DMSO (1:1 v/v) media. The addition of CN− to RS2 triggers an enhancement in fluorescence at 505 nm (green fluorescence), while the addition of Al(III) increases the fluorescence of the probe with a blue-shift of emission maximum by 25 nm (bluish-green fluorescence). The probe's action was investigated by 1H NMR titrations that indicate deprotonation of OH and NH moieties by these ions. 27Al NMR of RS2 -Al(III) complex suggests an octahedral geometry for the complex. The sensitivity of the fluorescent-based assays in aq. DMSO medium, 0.8 µM for CN− and 1.9 µM for Al(III) ions are far below the limits in the World Health Organization guidelines for drinking water. RS2 detects Al(III) by the chelation-enhanced fluorescence (CHEF) mechanism. Besides, RS2 was successfully applied to detect CN− and Al(III) ions in food materials and pharmaceutical samples, respectively. [ABSTRACT FROM AUTHOR]