Quantum chemical computations and photophysical spectral features studies of two coumarin compounds

An attempt was made to determine the ground state and excited state dipole moments and quantum chemical computations of two coumarin compounds, namely 3‐hydroxy‐3‐[2‐oxo‐2‐(2‐oxo‐2H‐chromen‐3‐yl)‐ethyl]‐1,3‐dihydro‐indol‐2‐one (3HOCE) and 3‐[2‐(8‐methoxy‐2‐oxo‐2H‐chromen‐3‐yl)‐2‐oxo‐ethylidene]‐1,3‐dihydro‐indol‐2‐one (3MOCE). Both compounds displayed a red shift with enhancement in solvent polarity. The larger excited state dipole moment indicated the more polar nature of the selected compounds in the excited state than in the ground state. Kinetic stability and chemical reactivity of the selected compounds were studied with help of the quantum chemical properties of the compounds such as frontier molecular orbital analysis using density functional theory calculations with B3LYP/6–311+G (d, p) basis sets. Molecular electrostatic potential, Mulliken charges, natural bond orbital, and nonlinear optical properties were further studied. NBO analysis showed proton transfer within the selected donor–acceptor, depicting the large energy of stabilization for the compounds. The calculated Fukui function inferred the local softness and electrophilicity indices of used solute compounds.