الفهرس 
Chapter OneOnly 14 pages are availabe for public view
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Abstract
3-formyl chromone and its derivatives are known to play an important role in biology and medicine. Thus, 3-formylchromone and its derivatives have been identified as effective herbicide, anxiolytic, anticonvulsant and human renin inhibitor. Some derivatives proved to be effective as immunostimulant. This later activity increases the interest in them and extensive studies have been reported.
The main features of the molecular electronic structure are of great relevance in understanding the biological activity of molecules.
The present work presents a detailed and thorough investigation of the electronic structure , spectra , Nonlinear optical Analysis (NLO) and Natural bond orbital analysis (NBO) of these compounds . Our ultimate aim, however, is to pinpoint those structural factors that underlie the biological activity of this class of compounds.
The present treatment starts by establishing the ground state geometry of 3-formyl chromone as a parent to the studied series of compounds. DFT/B3LYP method is used throughout the work. Due to the flexibility of the studied series of compounds an extended basis set is proposed. The 6-311G (d.p) basis set is thus used. The effect of polarization ”d” functions were examined. The gradient minimization technique was adopted to characterize the global minimum on the potential energy surface. This is further confirmed by computing and diogonilizing the matrix of the second derivative and establishing the existence of all positive eigen values.
The 6-311G (d,p) basis set seems to be much more capable of reproducing the geometry of the studied compounds in a cost-effective computation. The present study indicates the irrelevance of the ”d”-polarization function in describing the electronic environment of compounds . Throughout the present work, the 6-311G (d,p) basis set was adopted.
6-nitro 3-formylchromone is highly polar. The computed dipole moments range from a minimum value of 6.31200D for 3-formylchromone to a maximum value of 7.4901D for 6-nitro 3-formylchromone . The direction of the dipole moment, does, however, change slightly upon substitution.
The ground state properties of 1 and its derivatives show that compound 7 has the lowest EHOMO, ELUMO, and Egap indicating highest reactivity. from the computed dipole moment, compound 3 is found to have the highest polarity. Mullikan and natural charge distribution of the compounds 1–7 were studied which indicated the electronic charge distribution. The calculated dipole moment and first order hyperpolarizability results indicate that the molecule has a reasonable good non-linear optical behavior. MEP confirmed the different negative and positive potential sites of the molecule in accordance with the total electron density surface. Electronic absorption spectra are investigated experimentally in dioxane and ethanol; and theoretically in gas phase, dioxane and ethanol using CAM-B3LYP/6-311G (d, p). Compounds 1–6 exhibit 7 bands. The band maxima (λmax) and intensities of the spectra are found to have solvent dependence. The bands of compounds 1, 2, and 3 show blue shift, while compounds 4, 5 ,6 and 7 show red shift. Theoretical calculations of the vertical excitations at the CAM-B3LYP/6-311G (d, p) reproduce the experimental spectra, indicating a good agreement between theory and experiment. The NBO analysis of the compounds 1–7 indicated the intermolecular charge transfer between the bonding and antibonding orbital’s. The biological activity of the studied compounds show that compound 7(NO2) is the most active one ,whereas, the molecule 3 (di-CH3) is the least active and the order of reactivity is 7>6 > 5 > 4 > 1 > 2 > 3.