Fluoride anion sensing mechanism of 2‐(quinolin‐2‐yl)‐3‐hydroxy‐4H‐chromen‐4‐one chemosensor based on inhibition of excited state intramolecular ultrafast proton transfer

Abstract

The excited state hydrogen bonding interactions and intramolecular proton transfer (ESIPT) process for 2‐(quinolin‐2‐yl)‐3‐hydroxy‐4H‐chromen‐4‐one (Qu3HC) system has been theoretically studied via density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. We confirmed that the reversible tuning of intramolecular hydrogen bonding direction is impossible for Qu3HC system. Then, we have studied the S0‐state and S1‐state hydrogen bonding dynamical behaviors of Qu3HC structure and confirmed that the strengthening of intramolecular hydrogen bond in the S1 state could facilitate ESIPT reaction. Given photo‐induced excitation, we find that the charge redistribution around hydroxyl moiety plays important roles in providing driving force for ESIPT. Our constructed potential energy curves further verify that the ESIPT process of Qu3HC should be ultrafast due to low potential barrier. With the addition of fluoride anions, the exothermal deprotonation process occurs spontaneously along with the intermolecular hydrogen bond O–H···F, which reveals the uniqueness of detecting fluoride anion using Qu3HC molecule. As a whole, the fluoride anion inhibits the initial ESIPT process of Qu3HC, which results in different fluorescence behaviors.

Tuning ESIPT-coupled luminescence by expanding π-conjugation of a proton acceptor moiety in ESIPT-capable zinc(ii) complexes with 1-hydroxy-1H-imidazole-based ligands

“…However, the quinoline moiety is only rarely involved in the design and theoretical studies of ESIPT-capable molecules. [139][140][141][142][143][144][145][146][147][148][149][150][151][152][153][154][155][156] What is important for coordination chemistry in the case of HL q is that this new ESIPT-system still features a metal binding site and can be used for the synthesis of ESIPT-capable metal complexes as its predecessor HL p is. Finally, since ESIPT-fluorophores tend to luminesce with low quantum yields resulting from significant structural reorganization accompanying the ESIPT process, a natural choice for improving their efficiency through chelation-enhanced fluorescence (CHEF) seems to be Zn 2+ ion.…”

Fluorescence Sensors Based on Hydroxycarbazole for the Determination of Neurodegeneration-Related Halide Anions

“…Due to the presence of anions in the environment and their significant impact on health, analytical tools are needed to detect them. Fluorescent sensors are attractive for this purpose due to the excellent sensitivity of fluorescence as an analytical technique and the existence of a variety of events such as excited-state proton transfer (ESPT) [20][21][22][23], photoinduced electron transfer (PET), inter-or intramolecular charge transfer (ICT) or fluorescence resonance energy transfer (FRET) that can be successfully exploited for developing sensing compounds with satisfactory analytical features [24,25]. An elegant alternative for anion recognition consists of the interaction of the amino acid carboxylate group of tryptophan and phenylalanine with metals that have previously formed complexes (chelates) with functionalised tris(2-aminoethyl)amine linked to fluorescent moieties (anthracene, naphthalene...) [26].…”