Correlation between Excited-State Intramolecular Proton-Transfer and Singlet-Oxygen Quenching Activities in 1-(Acylamino)anthraquinones

Abstract

Excited-state intramolecular proton-transfer (ESIPT) and singlet-oxygen ((1)O2) quenching activities of intramolecularly hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means of static and laser spectroscopies. The ESIPT shows a substituent effect, which can be explained in terms of the nodal-plane model. The ESIPT activity positively and linearly correlates with their (1)O2 quenching activity. The reason for this correlation can be understood by considering ESIPT-induced distortion of their ground-state potential surface and their encounter complex formation with (1)O2. Intramolecularly hydrogen-bonded hydroxyanthraquinones found in aloe also show a similar positive and linear correlation, which can be understood in the same way.

Combined TDDFT and AIM Insights into Photoinduced Excited State Intramolecular Proton Transfer (ESIPT) Mechanism in Hydroxyl- and Amino-Anthraquinone Solution

“…1 ), including hydroxyl/dihydroxy-anthraquinone (HAQ/DHAQ) and 1-(acylamino)-anthraquinones (AYAAQs) 17 , 18 , 24 – 28 , exhibit the unique ESIPT properties, thus presenting emerging applications in fluorescence probes, dyes and drugs 29 – 33 . The experimental ESIPT evidences have been confirmed for 1-HAQ 34 – 37 , 1,5-DHAQ 37 – 39 , DCAQ and TFAQ 40 – 43 . However, 1,4-DHAQ 37 , 38 and AAAQ 40 – 43 with the similar molecular structures don’t show the ESIPT progress.…”

“…The experimental ESIPT evidences have been confirmed for 1-HAQ 34 – 37 , 1,5-DHAQ 37 – 39 , DCAQ and TFAQ 40 – 43 . However, 1,4-DHAQ 37 , 38 and AAAQ 40 – 43 with the similar molecular structures don’t show the ESIPT progress. More interestingly, 1,8-DHAQ 25 , 37 – 39 , 44 – 47 and CAAQ 40 – 43 switch their properties in different solvents.…”

“…However, 1,4-DHAQ 37 , 38 and AAAQ 40 – 43 with the similar molecular structures don’t show the ESIPT progress. More interestingly, 1,8-DHAQ 25 , 37 – 39 , 44 – 47 and CAAQ 40 – 43 switch their properties in different solvents. Blank et al .…”

“…The emission of CAAQ was mainly SWE and slight LWE 43 . When the solvent was changed to ethanol, LWE in CAAQ and DCAQ decreased greatly 40 . The substituent effect on ESIPT for AQs have been explained by nodal-plane model proposed in 1996 48 , which have also been widely explored and proved to be a reliable theory to study the ESIPT systems 49 – 51 .…”

Solvent Relaxation Accompanied Ultrafast Excited State Proton Transfer Dynamics Revealed in a Salicylideneaniline Derivative

“…The process, ESIPT, has been observed in derivatives of large class of molecules such as flavone, anthraquinone, quinolones, di and tri azoles, etc ,. In these molecules, the conversion of enol to keto form can vary depending on the medium and timescale of proton transfer process in the excited state.…”