Reflection And Discussion On Absorption Spectra

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3. Results and Discussion 3.1. Absorption spectra study of 5-aminopyridine Schiff base (L1 and L2): The absorption spectrum of probes L1 and L2 (40 μM) were investigated in the presence of metals ions in DMSO solvent. As shown in Fig. 1, Schiff base L1 exhibited absorption band at 269 nm, 310 nm, 323 nm and 347 nm; and L2 at 264 nm, 319 nm, 341 nm, 439 nm and 462 nm, that may be attributed to π-π* charge transfer transition. However, no remarkable changes were observed in absorption spectra after the addition of 1 equivalent various metal ions such as Ag(I), K(I), Li(I) Na(I), Co(II), Cu(II), Cd(II), Pb(II), Mg(II), Hg(II), Mn(II), Al(III), Cr(III), Gd(III) and Nd(III) ions. Interestingly upon the addition of zinc and nickel ions to the probe L1 absorbance peak shifted to higher wavelength (red shift) from 347 nm to 413 nm and 410 nm, respectively. Thus, L1-Zn(II) and L1+Ni(II) complexes exhibited color change from colorless to intense yellow color. Similarly, the addition of Fe(III) and UO2(II) to the probe L2, absorbance peak lead to decrease at 439/462 nm while new peak appear at 355 nm and 366/ 515 nm, respectively. Consequently, the absorbance peaks of L2-Fe(III) complexes shifted to UV-region, thus light yellow color turned to colorless, and in case of L2-UO2(II) complex absorbance peak showed red shift effect, that resulted in dark yellow color (Fig. 2a and b). Thus, absorption spectral changes were enabled to detect Ni(II), Zn(II), Fe(III) and UO2(II) as a naked eye
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