Solvent Polarity Dependent Excited State Dynamics of 2′-Hydroxychalcone Derivatives

Abstract

The excited-state properties of 4-(dimethylamino)methoxychalcones (DEAMC) and its derivative 4-(dimethylamino)hydroxychalcones (DEAHC) were investigated in various solvents with different polarities by using steady-state and femtosecond transient absorption spectroscopy combined with quantum chemical calculations. It is found that their photophysical parameters such as fluorescence quantum yields, lifetimes, and excited-state relaxation paths strongly depend on the solvent polarity. Quantum-chemical calculations elucidate that the geometry of DEAMC in the ground state is slightly torsional whereas DEAHC adopts a near planar conformation stabilized by O−H•••O chelated hydrogen bonds. Steady state spectra show that DEAHC is weak fluorescent in all solvents due to nonradiative relaxation in the excited enol and keto states, whereas the fluorescence quantum yield of DEAMC increases with the increasing of solvent polarities, and the emission yield is as large as 0.16 in acetonitrile. Femtosecond and nanosecond transient absorption spectra further prove that in nonpolar solvent the deactivation of S 1 in DEAMC is strongly governed by efficient formation of triplet states, whereas in polar solvent, stronger solvation induced energetically stabilization of ICT state, limiting the intersystem crossing to triplet state. The stabilization of ICT state not only leads to a higher fluorescence quantum yield for DEAMC but also restricts intramolecular twisting process in the enol form of DEAHC, facilitating efficient excited-state intramolecular proton-transfer reaction. These results clearly illustrate the dominant role of excited state solvation in modulating the emission behavior and deactivation mechanisms of fluorophores.

Solvent‐dependent ultrafast optical response of conjugated push–pull chromophores

“…The three components could also be used to fit the TA spectrum of C2B in DMSO. From the EADS results obtained from the fitting shown in Figure (c), it can be deduced that the increase in the environmental polarity led to vibrational thermal relaxation and the generation time of the ICT state would become longer . This outcome might be because the DA compound retained some polarity in the ground state, and the greater the polarity of the surrounding environment, the longer the solvation time that was required.…”

A novel donor–π–acceptor halochromic 2,6-distyrylnaphthalene chromophore: synthesis, photophysical properties and DFT studies

“…In other words, polar solvents can stabilize the excited state of the chromophore, decrease the energy level between the ground and excited state, and promote radiation less decay. [34][35][36] The absorption and emission spectra of the compound in xylene containing various amounts of triuoroacetic acid (TFA) were recorded to investigate the effect of pH on its photophysical. The obtained results are shown in Fig.…”

Molecular and crystalline requirements for solid state fluorescence exploiting excited state intramolecular proton transfer

“…[28][29][30][31][32][33] Chalcone-based compounds, comprising an aromatic ketone and enone system, have found application in both technological and biological settings. [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] The lasing prop- 1. [49][50][51] All reported quantum yields were obtained for single crystals, consequently the effect of trapping as a source of loss of efficiency can be ruled out.…”