Ultrafast Hydrogen Bond Strengthening of the Photoexcited Fluorenone in Alcohols for Facilitating the Fluorescence Quenching

Abstract

The time-dependent density functional theory (TDDFT) method was performed to investigate the excited-state hydrogen-bonding dynamics of fluorenone (FN) in hydrogen donating methanol (MeOH) solvent. The infrared spectra of the hydrogen-bonded FN-MeOH complex in both the ground state and the electronically excited states are calculated using the TDDFT method, since the ultrafast hydrogen-bonding dynamics can be investigated by monitoring the vibrational absorption spectra of some hydrogen-bonded groups in different electronic states. We demonstrated that the intermolecular hydrogen bond C=O...H-O between fluorenone and methanol molecules is significantly strengthened in the electronically excited-state upon photoexcitation of the hydrogen-bonded FM-MeOH complex. The hydrogen bond strengthening in electronically excited states can be used to explain well all the spectral features of fluorenone chromophore in alcoholic solvents. Furthermore, the radiationless deactivation via internal conversion (IC) can be facilitated by the hydrogen bond strengthening in the excited state. At the same time, quantum yields of the excited-state deactivation via fluorescence are correspondingly decreased. Therefore, the total fluorescence of fluorenone in polar protic solvents can be drastically quenched by hydrogen bonding.

Validation and Divergence of the Activation Energy Barrier Crossing Transition at the AOT/Lecithin Reverse Micellar Interface

“…Coumarin 102 33 ) in recent literature. [34][35][36][37] In a recent spectroscopic study 32 on the hydrogen-bonding properties of C-500, it has been demonstrated that the quantum yield of the dye C-500 in hexane (devoid of hydrogen bonding, Φ ) 0.76) is comparable to those in CHCl 3 (hydrogen-bond donor, Φ ) 0.81) and THF (hydrogen-bond acceptor, Φ ) 0.81). However, the emission characteristics of other coumarin dyes (e.g., C-151, C-35) are demonstrated 32 to be heavily dependent on the HB properties of the solvents used.…”

Wagging motion of hydrogen-bonded wire in the excited-state multiple proton transfer process of 7-hydroxyquinoline·(NH3)3 cluster

“…However, little is known about electronic excited-state hydrogen bond, because the structure and dynamics of which are difficult to analyze for both theoretical and experimental studies. Recently, Zhao and Han [12][13][14][15][16][17][18][19] have determined theoretically that intermolecular hydrogen bonds between solute and alcoholic molecules can be significantly strengthened in the electronic excited state upon photoexcitation. In previous works [20][21][22][23], we have demonstrated that, the excited-state hydrogen bonding behavior would play an important role in many photochemical reactions such as fluorescence quenching [20], excited-state proton transfer [21], tuning effects on photochemistry [22].…”

Hydrogen-bonding study of photoexcited 4-nitro-1,8-naphthalimide in hydrogen-donating solvents

“…Experiments performed using the femtosecond time-resolved vibrational spectroscopy have shown the potential to monitor hydrogen-bonding dynamics. Hydrogen-bonding dynamics always occurs on ultrafast timescales, which plays an increasingly important role in many photophysical processes and photochemical reactions [41][42][43][44][45][46][47][48][49][50][51][52][53]. It has been confirmed by Zhao et al that the intermolecular hydrogen bond in many molecular systems is greatly strengthened in the electronically excited state.…”

“…It has been confirmed by Zhao et al that the intermolecular hydrogen bond in many molecular systems is greatly strengthened in the electronically excited state. Electronic excite-state hydrogen bond strengthening is closely linked with many ultrafast radiationless deactivation processes, such as ultrafast internal conversion(IC) [43] and intersystem crossing (ISC) [41], vibrational energy relaxation (VER) [54], twisted intramolecular charge transfer(TICT) [47] and intermolecular photoinduced electron transfer (PET) [45].…”