Optical properties and fluorescence quenching of biologically active ethyl 4-(4-N,N-dimethylamino phenyl)-2-methyl-5-oxo-4,5-dihydro-1H-indeno[1,2-b]pyridine-3-carboxylate (DDPC) dye as a probe to determine CMC of surfactants

Abstract

4-(4-N,N-Dimethylamino phenyl)-2-methyl-5-oxo-4,5-dihydro-1H-indeno[1,2-b]pyridine-3-carboxylate (DDPC) was prepared via the multi-component reaction of indane-1,3-dione with 4-(dimethylamino)benzaldehyde, ethyl acetoacetate and ammonium acetate. Data obtained from FT-IR, ¹H-NMR, ¹³C-NMR, EI-MS and elemental analysis were consistent with the chemical structure of the newly prepared DDPC. Electronic absorption and emission spectra of DDPC were measured in different solvents. The DDPC dye exhibits a red shift in its emission spectrum as the solvent polarity increases, indicating a large change in the dipole moment upon excitation due to intramolecular charge transfer within the excited DDPC molecules. Excited state intermolecular hydrogen bonding has an effect upon the energy of the emission spectrum and the fluorescence quantum yield of the DDPC molecules. The DDPC dye undergoes solubilization into different micelles and can be used as a probe to determine the critical micelle concentration (CMC) of SDS and CTAB. The DDPC dye can also be used to probe of the polarity and hydrogen bonding properties of its local micro-environment. The antibacterial activity of DDPC was tested in vitro for the first time by using a disk diffusion assay against two Gram-positive and two Gram-negative bacteria, and the minimum inhibitory concentration (MIC) was also determined with reference to the standard drug tetracycline.