Computational Studies of the Role of Substituents on the Reactivity and Biological Activities of Naphthoic Acid

Substituents play a major role in influencing the reactivity and biological activity of aromatic compounds. Substituents affect the conductivity of molecular electronic and photoresponsive switches, light harvesting dye-sensitized solar cells and organic electroluminescent devices. A number of quantum mechanical methods corresponding to stabilization energy, charge of substituent active region, energy dispersive analysis, and molecular electrostatic potential help in the description of substituent effect in aromatic systems. In the present work we carried out computational studies for the estimation of chemical and structural properties of a chemical library of nine ortho substituted naphthoic acids. The chemical reactivity of the selected substituted naphthoic acids was assessed from a number of physicochemical properties such as total energy, HOMO-LUMO gap, chemical hardness, binding energy, ionization potential, electron affinity, electronegativity, electrochemical potential, global softness, electrophilicity and dipole moment. The effect of the electron-donor groups on conjugation of ortho substituted naphthoic acid was investigated by correlating the calculated rotational barriers of transition state of cis and trans ortho-substituted naphthoic acids to observe change in single bond length, double bond length, bond angle, dihedral angle, and rotational frequency of carboxylic group of substituted napthoic acids. The rotational barrier correlated with the geometric, atomic, molecular, and spectroscopic parameters. Moreover, quantitative structure–activity relationship (QSAR) analyses was performed and the obtained structural properties were linked with biological activities.