Synthesis and crystallographically characterized thiadiazole derivative as an efficient Fe3+ selective fluorescent probe

A thiadiazole derivative, 2-((napthalen-2-yl)methylthio)-5-((napthalen-7-yl)methylthio)-1,3,4 thiadiazole (L-1) has been synthesized and well characterized by different analytical techniques, viz. H-1 NMR, QTOF mass spectra, elemental analysis, FTIR and, its structure has been confirmed by single crystal X-ray structure analysis. Two naphthalene units of two molecules in a unit cell are parallel to each other through pi-pi stacking interaction while S atoms are involved in n-pi* interaction with vacant pi* orbital of naphthalene unit. The binding of L-1 with Fe3+ has been established from FTIR, thermal and mass spectral analysis of the product. The composition of the complex (Fe3+: L-1 = 1 : 1, mole ratio) in solution has been evaluated by Job's plot. The probe has been used for trace level determination of Fe3+ by, fluorescence technique. L-1 has an excitation and emission maxima at 370 nm and 440 nm respectively. The binding constant of L-1 for Fe3+ has been estimated from Stern-Volmer method as 7.9 x 10(3). The limit of detection is 8 x 10(-7) M.