ESIPT and Photodissociation of 3-Hydroxychromone in Solution: Photoinduced Processes Studied by Static and Time-Resolved UV/Vis, Fluorescence, and IR Spectroscopy

Abstract

The spectral properties of fluorescence sensors such as 3-hydroxychromone (3-HC) and its derivatives are sensitive to interaction with the surrounding medium as well as to substitution. 3-HC is a prototype system for other derivatives because it is the basic unit of all flavonoides undergoing ESIPT and is not perturbed by a substituent. In this study, the elementary processes and intermediate states in the photocycle of 3-HC as well as its anion were identified and characterized by the use of static and femtosecond time-resolved spectroscopy in different solvents (methylcyclohexane, acetonitrile, ethanol, and water at different pH). Electronic absorption and fluorescence spectra and lifetimes of the intermediate states were obtained for the normal, tautomer and anionic excited state, while mid-IR vibrational spectra yielded structural information on ground and excited states of 3-HC. A high sensitivity on hydrogen-bonding perturbations was observed, leading to photoinduced anion formation in water, while in organic solvents, different processes are suggested, including slow picosecond ESIPT and contribution of the trans-structure excited state or a different stable solvation state with different direction of OH. The formation of the latter could be favored by the lack of a substituent increasing contact points for specific solute-solvent interactions at the hydroxyl group compared to substituted derivatives. The effect of substituents has to be considered for the design of future fluorescence sensors based on 3-HC.

Excited-state intramolecular proton transfer of 2-acetylindan-1,3-dione studied by ultrafast absorption and fluorescence spectroscopy

“…Depending on the solvent, fluorescence spectra comprise contributions from both S 1 A and S 1 B , giving rise to “dual” fluorescence 19 . Since ESIPT is ultrafast, emission yields from the excited reactant state however may be very low (see, e.g., in Ref.…”

Exploration of the Fluorescent Properties and the Modulated Activities against Sirtuin Fluorogenic Assays of Chromenone-Derived Natural Products

“…Commercially available 7-amino-4-methylcoumarin (AMC) is commonly used in various biological studies, and in particular AMC was used to develop a fluorescent turn-on enzymatic assays to study a large range of proteins including histone deacetylase (HDAC) [ 11 ], sirtuin (SIRT) [ 12 ], amidase [ 13 ], transglycosylase [ 10 ], and alkaline phosphatase (ALP) [ 14 ]. 7-Hydroxyisoflavones and 3-hydroxyflavones also exhibit fluorescence in biological buffers [ 15 , 16 ]. In our previous studies, we reported the development of 3-alkyl-6-methoxy-7-hydroxychromones (AMHC) as a fluorogenic scaffold for biological studies, which displays comparable fluorescent properties to AMC [ 7 ].…”

A combined IR/IR and IR/UV spectroscopy study on the proton transfer coordinate of isolated 3-hydroxychromone in the electronic ground and excited state

“…Thus a substituent on the chromone unit as the phenyl group in 3-HF might even promote a faster ESPT since it hinders specific solute-solvent interactions enabling the pathway via the stabilised trans structure. 50,51 Further theoretical investigations on the structure and reactivity of 3-HC are presented in ref. 32 and 52-54. In order to achieve more information on the structure and reactivity of isolated 3-HC and defined aggregates with water we present in this paper the first molecular beam investigations of 3-HC including mass selected IR spectroscopy for the electronic ground state (IR/R2PI method) and the electronically excited state (UV/IR/UV method).…”