Adaptable sensor for paying fluorometric detection of methanol molecules: theoretical aspects and DNA binding studies
The multifunctional Schiff base ligand N,N’-bis(5-nitro-salicylaldehyde)azine (NO2-H2SALNN) has been successfully synthesized and characterized by ESI-MS+, 1H-NMR spectroscopy and CHN elemental analysis. The very feeble intrinsic fluorescence exerted by the ligand was found to be enhanced by several folds in the presence of methanol (~168 fold) and water (~10 fold) molecules. This enhancement of fluorescence intensity is supposed to be occurs as the result of blocking of rotational isomerization along the azomethine group (C=N)due to its coordination with solvent molecules, thereby exhibiting turn on fluorescence at two distinct wavelengths in presence of methanol and water having much difference of two emission wavelengths(Δλ = 125 nm).The hydrogen bond assisted enhancement fluorescence (HAEF) for methanol and water at two different wavelengths giving two different emissions may be due to the different size/nature of solvent as well as differences in solvent polarity. The binding of the NO2-H2SALNN and the solvent molecules were investigated and described by spectroscopic and computational studies. The bioactivity of NO2-H2SALNN has also been inspected by DNA binding measurements through spectrometric and thermodynamic studies. DNA binding studies reveal that the ligand interacts with double stranded CT-DNA through groove binding mode and the intrinsic binding constant was determined by calorimetric studies to be (2.24 ± 0.04) × 105 M−1.