A DFT/TD-DFT Study on the ESIPT-Type Flavonoid Derivatives with High Emission Intensity

Abstract

To reveal the influence of different substituents on the excited-state intramolecular proton transfer (ESIPT) process and photophysical properties of 4′-N, N-dimethylamino-3-hydroxyflavone (DMA3HF), two novel molecules (DMA3HF-CN and DMA3HF-NH2) were designed by introducing the classical electron-withdrawing group cyano (-CN) and electron-donating group amino (-NH2). The three molecules in the acetonitrile phase were systematically researched by applying the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The excited-state hydrogen bond enhancement mechanism was confirmed, and the hydrogen bond intensity followed the decreasing order of DMA3HF-NH2 > DMA3HF > DMA3HF-CN, which can be explained at the electronic level by natural bond orbital, fuzzy bond order, and frontier molecular orbital analyses. Moreover, we found from the electronic spectra that the fluorescence intensity of the three molecules in keto form is relatively strong. Moreover, the calculated absorption properties indicated that introducing the electron-withdrawing group -CN could significantly improve the absorption of DMA3HF in the ultraviolet band. In summary, the introduction of an electron-donating group -NH2 can promote the ESIPT reaction of DMA3HF, without changing the photophysical properties, while introducing the electron-withdrawing group -CN can greatly improve the absorption of DMA3HF in the ultraviolet band, but hinders the occurrence of the ESIPT reaction.

Spectroscopic Insights of an Emissive Complex between 4′-N,N-Diethylaminoflavonol in Octa-Acid Deep-Cavity Cavitand and Rhodamine 6G

“…In previous work [32], we studied the influence of the confined environment on 3-hydroxyflavone (3HF) and 4 -N,N-diethylaminoflavonol (DEA3HF), which can proton-transfer in the excited state by the ESIPT (Excited State Intramolecular Proton Transfer) process. In this study, we observed that the dyes had a photophysical behavior close to that observed in an organic solvent solution; even encapsulated and solubilized in water, important properties were preserved, such as photochemical and photophysical stability and a large Stokes shift [33]. The solubility of organic dyes is often limited to organic solvents, and the use of the supramolecular approach, which involves confining a capsule with a water-soluble hydrophobic interior, using the OA capsule as the medium for this, significantly expands the study and applications of fluorescent compounds [34][35][36].…”

Endoplasmic Reticulum-Targeted Two-Photon Fluorescent Probe for the Detection of Nitroxyl in a Parkinson’s Disease Model

“…These result in bright fluorescence emission from KD-OH. 35,37 Application of KD-HNO in Living Cells. Based on the remarkable spectral performance of KD-HNO, we applied it to the biological sensing of HNO.…”

“…Thus, the KD-OH readily undergoes a rapid conversion from the enol form to the keto form in the excited state, forming a strong intramolecular hydrogen bond. These result in bright fluorescence emission from KD-OH . , …”

Excited‐State Proton Transfer in Luminescent Dyes: From Theoretical Insight to Experimental Evidence

“…After the theoretical approach has been validated, the model can be further characterized through topological analysis. [56] This analysis is especially useful for the characterization of the hydrogen-bond strength, [57] because as a rule of thumb, a dye is more prone to suffer ESIPT if it presents a stronger intramolecular hydrogen bond. [58] The analysis of Non-Covalent Interactions (NCI) allows a further refinement of the description.…”