ABSTRACT
24Coumarins are of great interest in the field of research because of their tremendous biological properties. It makes these compounds so attractive for further backbone derivatisation and screening to meet specific applications. The present study depicts the correlation between structural variations of Coumarin (C), its metabolite 3,4-dihydrocoumarin (DC) and their respective substituted compounds with chemical reactivity which in turn correlates to the influence of α,β unsaturation on structures. All Quantum mechanical computational calculations are done in density functional theory (DFT) method using the Gaussian 09W simulation package. The geometries and energies of these molecules have been computed at B3LYP/6–311G (2d, 2p) level of theory. Natural Bond Orbital (NBO) analysis of these molecules provides a quantitative evaluation of electron density distribution and which is used to make a qualitative conclusion of donor-acceptor properties of substituents with parent C and DC scaffolds. It helps to predict the reactive centers and nature of feasible reactions in the presence of ring activating and deactivating groups. Time dependent density functional theory (TD-DFT) based computation is adopted for the evaluation of absorption (UV-Vis) spectra of the molecules under consideration by including one set of diffuse function in basis set, which is utilized to analyze the shifting of absorption maxima as the consequence of different types of substituents on third position of the parent scaffold. The calculation of dipole moment, polarization and hyper polarization are showing the extent of the application of these compounds in the field of nonlinear optical organic materials. Global reactive descriptors like ionization potential, electron affinity, electronegativity, electrophilicity, softness, hardness, etc., are calculated in order to analyze the extent of reactivity of considering molecules. The local reactivity descriptors such as Fukui functions and relative nucleophilicity were also calculated for the better understanding of the nature of reactive site and attempted to predict the type of reactions that are preferable for the considering chemical systems. In addition to Quantum mechanical calculation, druggability of some important hydroxy coumarin systems were also examined using Molinspiration property calculator available online.
