Excited State Properties of 7-Hydroxy-4-methylcoumarin in the Gas Phase and in Solution. A Theoretical Study

Abstract

TDDFT/B3LYP and RI-CC2 calculations with different basis sets have been performed for vertical and adiabatic excitations and emission properties of the lowest singlet states for the neutral (enol and keto), protonated and deprotonated forms of 7-hydroxy-4-methylcoumarin (7H4MC) in the gas phase and in solution. The effect of 7H4MC-solvent (water) interactions on the lowest excited and fluorescence states were computed using the Polarizable Continuum Method (PCM), 7H4MC-water clusters and a combination of both approaches. The calculations revealed that in aqueous solution the pi pi* energy is the lowest one for excitation and fluorescence transitions of all forms of 7H4MC studied. The calculated excitation and fluorescence energies in aqueous solution are in good agreement with experiment. It was found that, depending on the polarity of the medium, the solvent shifts vary, leading to a change in the character of the lowest excitation and fluorescence transition. The dipole-moment and electron-density changes of the excited states relative to the ground state correlate with the solvation effect on the singlet excited states and on transition energies, respectively. The calculations show that, in contrast to the ground state, the keto form has a lower energy in the pi pi* state as compared to enol, demonstrating from this point of view the energetic possibility of proton transfer from the enol to the keto form in the excited state.

Vibrational analysis of trans‐stilbene in the excited singlet state by time‐dependent density functional theory: calculations of the Raman, infrared, and fluorescence excitation spectra

“…Sobolewski and Domcke 26 have applied TD-DFT to the calculation of the infrared spectra of anthranilic acid and salicylic acid in electronic excited states. Catalán et al 27 and Georgieva et al 28 have utilized the analytic gradient based on TD-DFT to study the excited state properties of 7-hydroxy-4-methylcoumarin and the excited-state proton transfer in 3-methyl-7-azaindole dimer, respectively.…”

Red Emitting Coumarins: Insights of Photophysical Properties with DFT Methods

“…The emission calculations with various functionals highlight the utility of the B3LYP functional to compute the emission energies of such kind of molecules. In the literature, the B3LYP functional has been successfully employed for estimating the vertical excitations of coumarin dye molecules [77,78].…”

Kinetics of catalyzed hydrolysis of 4-methylumbelliferyl caprylate (MUCAP) salmonella reagent

“…The effect of solvents, substituents and temperature on the various photophysical properties of coumarin compounds have been reported [11][12][13][14][15].…”