Shimaa Abdel Halim

Synthesis, molecular, electronic structure, linear and non-linear optical and phototransient properties of 8-methyl-1,2-dihydro-4H-chromeno[2,3-b]quinoline-4,6(3H)-dione (MDCQD): Experimental and DFT investigations

Base catalysed ring opening ring closure (RORC) reaction of 6-methylchromone-3‑carbonitrile (1) with 1,3-cyclohexanedione afforded 8-methyl-1,2-dihydro-4H-chromeno[2,3-b]quinoline-4,6(3H)-dione (MDCQD). Theoretical calculations by Density Functional Theory (DFT) at the B3LYP/6-311G (d,p) level of theory was utilized to illustrate the equilibrium geometries of MDCQD. Also, the nonlinear optical properties, simple harmonic vibrational frequencies, thermo-chemical parameters and Mullikan atomic charges were calculated. In addition, the electronic absorption spectra in polar and non polar solvents were discussed on the basis of TD-DFT calculations. A nanofiber-like structure with high aggregation was resolved by using scanning electron microscopy images and its particle sizes were measured by particle size analyzer. The spectroscopic characteristics of the prepared thin film of MDCQD were studied in a wide spectral range of 200-2500nm. The analysis of the absorption edges affords two direct optical band gaps with energies of 1.00 and 2.76eV. A characteristic emission peak of photoluminescence spectrum in the visible region was detected and has a red-shift as a result of solvent polarity. The MDCQD film based heterojunction showed rectification behavior and diode-like characteristics. The photovoltaic characteristics under illumination of 100mW/cm2 were studied. The open-circuit voltage and short-circuit current were found to be 0.22V and 4.25×10-7A/cm2, respectively. Moreover, the prepared heterojunction showed remarkable phototransient characteristics which afford the probability for the operation as a photodiode.

DFT calculations and electronic absorption spectra of some, α- and γ-pyrone derivatives

The electronic absorption spectra of 6-ethyl-4-hydroxy-2,5-dioxo-pyrano[3,2-c] quinoline 1, 6-ethyl-4-hydroxy-3-nitro-2,5-dioxo-pyrano[3,2-c] quinoline 2, 6-ethyl-4-chloro-2,5-dioxo-pyrano[3,2-c] quinoline 3, 6-ethyl-3-nitro-4-chloro-2,5-dioxo-pyrano[3,2-c] quinoline 4, 6-ethyl-4,5-dioxopyrano[3,2-c] quinoline 5, and 6-ethyl-3-nitro-6H-pyrano [3,2-c]quinoline-4,5-dione 6, were measured in polar (methanol) as well as nonpolar (dioxane) solvents. The geometries were optimized using B3LYB/6-311G (p,d) method. The most stable geometry of the studied compounds, 1-6, is the planar structure as indicates by the values of the dihedral angles. The insertion of a nitro group in position 3 in both α- and γ-pyrone ring decreases the energy gap and hence increases the reactivity of 3 and 6 compounds. Assignment of the observed bands as localized, delocalized and/or of charge transfer (CT) has been facilitated by TD-DFT calculations. The correspondences between the calculated and experimental transition energies are satisfactory. The solvent and substituent effects have been investigated. Chloro-substituent has a higher band position and intensity effects on the spectra more than hydroxyl or nitro groups.

Theoretical Study and Experimental Analysis on 2-(1-Ethyl-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)-2-oxoacetic Acid ( 3 ) Using the DFT Approach

Riley oxidation of 3-acetyl-4-hydroxyquinolin-2(1H)-one (1) with selenium dioxide furnished the unexpected product 2-(1-ethyl-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)-2-oxoacetic acid (3). The expected product 2-(1-ethyl-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)-2-oxoacetaldehyde (2) was excluded based on the spectral data. The elemental analysis and spectral data (IR, and 1H NMR) was used to deduce the structure of compound 3. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations of the electronic structure at the B3LYP/6-311G (d,p) level of theory have been employed for compound 3 to investigated its geometry, linear polarizability 〈Δα〉, first-order hyperpolarizability 〈β〉, natural bonding orbital (NBO), molecular electrostatic potential contours (MEP and ESP), electrophilicity, and UV–Vis spectra in both ethanol and dioxane solvents. The geometrical and energetic parameters have been extensively investigated to reveal the reason behind the selective formation of compound 3, rather than the expected product 2. FT-IR spectra in the solid phase were recorded for compound 3. The thermo-chemical parameters, harmonic vibration frequencies, and the equilibrium geometries have been calculated at the DFT/B3LYP/6-311G (d,p) level. Time-dependent density functional theory (TD-DFT) was used to calculate the excited states of compound 3. Changes in the solvent cause changes in the band intensities and in the positions of the band maxima (λmax). The excited state was identified and contributes to the electronic configurations, and it was characterized in terms of the relevant MOs. The theoretical spectra were computed using the Coulomb-attenuating method (CAM-B3LYP), using the basis set 6-311G (d,p) in the gas phase, and the polarizable continuum model (PCM) in dioxane and ethanol. The results indicate good agreement with the observed spectra.