The sensing mechanism of fluorescent probe for PhSH and the process of ESIPT

Abstract

The detection mechanism of fluorescent probe FQ-DNP (DNP: 2,4-dinitropheno) for PhSH and the detailed ESIPT process of its product 2-(6-(diethylamino) quinolin-2-yl)-3-Hydroxy-4H-chromen-4-one (FQ-OH) have been revealed by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). For FQ-OH, the decreased bond length of H 6 -N 7 and RDG analysis illustrate that the strength of hydrogen bond H 6 -N 7 has been enlarged after photoexcitation, creating a good condition for ESIPT. To illustrate the ESIPT process in detail, the potential energy curves are performed and the transition state reaction energy is calculated. In the S 0 state, the FQ-OH could happen proton transfer (PT) to form keto, but the keto form is more unstable than enol form. After photoexcitation, in the S 1 state, FQ-OH could happen PT to produce stable keto form. Excited dynamic simulation shows that PT happens at 71.5 fs. The calculated absorption and emission spectra are in agreement with the experimental data, and the calculated Stokes shift is 160 nm. Frontier molecular orbitals (FMOs) and hole-electron analysis show that twisted intramolecular charge transfer (TICT) is responsible for the fluorescent quenching of FQ-DNP.

Isoacridone dyes with parallel reactivity from both singlet and triplet excited states for biphotonic catalysis and upconversion

“…24,25 Against this background, there is increased interest in developing photosensitizers made from abundant rst-row transition metal complexes, [26][27][28][29][30] and purely organic (metal-free) alternatives. [31][32][33][34][35] Organic PS could be more amenable to larger scale applications, [36][37][38] and numerous organic PS such as xanthene-type dyes (eosin Y, uorescein), 39,40 cyanoarenes, 31,41 anthraquinones, 42,43 avins, [44][45][46] BODIPY, [47][48][49][50] and others are already known. [51][52][53][54][55] The performance of organic photosensitizers can be limited by several factors including modest excited-state redox potentials, 56 visible light absorption, [51][52][53][54][55] or (photo)stability, 57 but inefficient ISC to access photoactive triplet-excited states appears to be among the primary limitations.…”

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.…”

A Deep Understanding on the Effective Generation of Twisted Intramolecular Charge Transfer by Protonation in Thiazolo[5,4-d]thiazole Derivatives

“…Generally, it is known that the intramolecular H-bond between the proton donor (−NH 2 or −NH 3 ) and the proton acceptor (=N– in (bi)­heterocycle group) is the internal driving force for the occurrence of ESIPT. , Hence, in order to further reveal the crucial factor related to the original ESIPT process, the independent gradient model (IGM) and the atoms in molecules topology analysis (AIM) were performed to verify the influence of protonation on the H-bond strength of the three kinds of molecules. For the unprotonated DA-TzTz, the peak of the discrete plots locates at negative sign­(λ 2 )­ρ with a value of −0.04 and the δg of the highest discrete plots peak locates around 0.08, implying a typical H-bond attraction (Figure a).…”