Modeling Excited States of Fluorescent Compounds with UV-Vis Spectra Calculations

Abstract: Fluorescence is the property where molecules absorb electromagnetic radiation usually in the ultraviolet range and re-emit light in greater wavelengths, usually in the visible light range. We investigated the fluorescent molecules DMABN, ABN, MABN, MMD, caffeine, anthracene, salicylamide, and acetyl anthranilic acid through excited state computational chemistry calculations and observed the excited state quantum descriptors with a focus on peak absorbance wavelength, excitation energy, and oscillator strength. Calculations were run with DFT theory TD-B3LYP and a 3-21G basis set. The excited state that contributes most to the absorption peak of a molecule is shown by the largest oscillator strength, and the difference between the corresponding excitation energy and the LUMO was found. This value was compared to the HOMO-LUMO gap to determine the amount of extra energy required for electrons to move to the excited state. Key words: excited states, DMABN, UV-Vis spectrum, oscillator strength, HOMO-LUMO ga