Subpicosecond UV-pump and IR-probe Spectroscopy of 9-Fluorenone in Deuterated Acetonitrile and Methanol

Hirai, Satori; Banno, Motohiro; Ohta, Kaoru; Palit, Dipak K.; Tominaga, Kazuhiro

doi:10.1246/cl.2010.932

Cited by 10 publications

(16 citation statements)

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“…15 Tominaga and co-workers reinvestigated the hydrogen bond dynamics in the excited state of FL in CD 3 OD using subpicosecond-resolved visible pump−IR probe spectroscopy to show hydrogen bond-breaking and -reorganization processes. 27,28 Han et al, however, advocated hydrogen bond strengthening upon electronic excitation of these chemical systems from the results of time-dependent density functional theory calculations. 19,20 FL has a single hydrogen bond-accepting site (CO group) and forms 1:1 and/or 1:2 hydrogen-bonding complexes with hydrogen bond-donating solvents through association with either and both of the available lone pairs of electrons on the oxygen atom of the carbonyl group, respectively (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Dynamics of Hydrogen Bond Breaking and Making in the Excited State of Fluoren-9-one: Time-Resolved Visible Pump–IR Probe Spectroscopic Study

et al. 2017

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The fluoren-9-one (FL) molecule, with a single hydrogen bond-accepting site (C═O group), has been used as a probe for investigation of the dynamics of a hydrogen bond in its lowest excited singlet (S) state using the subpicosecond time-resolved visible pump-IR probe spectroscopic technique. In 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), a strong hydrogen bond-donating solvent, the formation of an FL-alcohol hydrogen-bonded complex in the ground electronic (S) state is nearly complete, with a negligible concentration of the FL molecule remaining free in solution. In addition to the presence of a band due to the hydrogen-bonded complex in the transient IR spectrum recorded immediately after photoexcitation of FL in HFIP solution, appearance of the absorption band due to a free C═O stretch provides confirmatory evidence of ultrafast photodissociation of hydrogen bonds in some of the complexes formed in the S state. The peak-shift dynamics of the C═O stretch bands reveal two major relaxation pathways, namely, vibrational relaxation in the S state of the free FL molecules and the solvent reorganization process in the hydrogen-bonded complex. The latter process follows bimodal exponential dynamics involving hydrogen bond-making and hydrogen bond-reorganization processes. The similar lifetimes of the S states of the FL molecules, both free and hydrogen-bonded, suggest establishment of a dynamic equilibrium between these two species in the excited state. However, investigations in two other weaker hydrogen bond-donating solvents, namely, trifluoroethanol (TFE) and perdeuterated methanol (CDOD), reveal different features of peak-shift dynamics because of the prominence of the vibrational relaxation process over the hydrogen bond-reorganization process during the early time.

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Section: Introductionmentioning

confidence: 99%

Ultrafast Dynamics of Hydrogen Bond Breaking and Making in the Excited State of Fluoren-9-one: Time-Resolved Visible Pump–IR Probe Spectroscopic Study

et al. 2017

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“…The hydrogen bonds inuence various properties of the solute, such as its electronic states and the relaxation processes. 9-Fluorenone (FL) has a carbonyl group which can form hydrogen bonds, and spectroscopic studies [9][10][11][12][13][14] as well as theoretical calculations 15 have been reported on the nature of the excited state of FL. The vibrational dynamics of FL in alcohol solutions have been reported in the electronic ground state 12 and the excited state.…”

Section: Introductionmentioning

confidence: 99%

“…The vibrational dynamics of FL in alcohol solutions have been reported in the electronic ground state 12 and the excited state. 10,13,14 Using sub-picosecond UV-pump infrared (IR)-probe spectroscopy we have observed transient IR absorption spectra of FL in acetotrnile-d 3 and methanol-d 4 . 13 By comparison with theoretical calculations of the vibrational structure in the S 1 state, 15 we assigned the vibrational bands observed in the transient spectra.…”

Section: Introductionmentioning

confidence: 99%

“…10,13,14 Using sub-picosecond UV-pump infrared (IR)-probe spectroscopy we have observed transient IR absorption spectra of FL in acetotrnile-d 3 and methanol-d 4 . 13 By comparison with theoretical calculations of the vibrational structure in the S 1 state, 15 we assigned the vibrational bands observed in the transient spectra. In this study, we used sub-picosecond visible-pump and IR-probe spectroscopy to study the effects of hydrogen bonding on the vibrational structures and vibrational dynamics of the CO stretching mode of the excited state FL in various solvents, including aprotic solvents.…”

Section: Introductionmentioning

confidence: 99%

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Vibrational dynamics of the CO stretching of 9-fluorenone studied by visible-pump and infrared-probe spectroscopy

2015

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We studied the effects of hydrogen bonds on the vibrational structures and vibrational dynamics of the CO stretching mode of 9-fluorenone (FL) in the electronically excited state in aprotic and protic solvents using sub-picosecond visible-pump and IR-probe spectroscopy. The transient IR spectrum of the CO stretching band in methanol-d4 has two bands at 1529.9 cm(-1) and 1543.4 cm(-1), which are assigned to an FL-solvent complex and free FL, respectively. In the aprotic solvents, the CO stretching bands show blue-shifts in time. This shift is due to vibrational cooling, which is derived from anharmonic couplings with some low-frequency modes. Interestingly, a red-shift is observed at later delay time for the band at 1529.9 cm(-1) in methanol-d4. A possible mechanism of this spectral shift is related to the hydrogen bond dynamics between the solute and solvent.

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“…Ultrafast vibrational spectroscopy has been proven to be a powerful technique as it probes the vibrational frequency changes in real time and the vibrational frequencies are often exquisitely sensitive to the H-bond interaction. In recent years, time-resolved infrared (TRIR) spectroscopy has been explored in great detail, which has advanced the microscopic understanding of static and dynamic features of H-bonding in equilibrium and nonequilibrium conditions. − Hydrogen bonding reorganization and fluctuation around a solute significantly influence charge transfer, electron transfer, and excited-state deactivation processes of the solute. Real-time measurements of H-bond formation and reorganization provide a detailed picture of the site-specific interaction between solute and solvent molecules and bring mechanistic insight into hydrogen-bond-induced chemical and photochemical reactivity.…”

Section: Introductionmentioning

confidence: 99%

Disentangling Time Scales of Vibrational Cooling, Solvation, and Hydrogen Bond Reorganization Dynamics Using Ultrafast Transient Infrared Spectroscopy of Formylperylene

2019

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Unraveling dynamics of solvation and hydrogen bond (H-bond) reorganization between a solute and solvent is crucial to understand the importance of specific and nonspecific interactions in a solution-phase chemical reaction. Ultrafast time-resolved infrared (TRIR) spectroscopy provides direct opportunity to monitor site-specific intermolecular dynamics on a real-time scale by probing vibrational marker bands in the excited state of a solute. Herein, we report the real-time dynamics of vibrational cooling, solvation, and hydrogen bond reorganization of formylperylene (FPe) through TRIR spectroscopy of carbonyl (CO) stretching mode in nonpolar, polar aprotic, and polar protic solvents. High sensitivity of the CO stretch frequency (υ̅CO) to photoinduced intramolecular charge transfer processes induced by specific and nonspecific solvent interactions led us to monitor the dynamics of dipolar solvation, site-specific H-bond formation, and reorganization processes by the TRIR method. In nonpolar cyclohexane, the υ̅CO stretch band appears at 1610 cm–1 and exhibits negligible spectral shift over several tens of picoseconds. In acetonitrile, the υ̅CO peak shifts to 1594 cm–1 and exhibits a further temporal red shift of about 5 cm–1 with a characteristic solvation time scale of acetonitrile (τ ∼ 0.5 ps). In methanol, υ̅CO exhibits two bands corresponding to free and H-bonded FPe in early time scale. The free FPe population converts to the hydrogen-bonded population with a lifetime of about 10 ps. Vibrational cooling (τvc ∼ 12–20 ps) in the excited electronic state of FPe could independently be monitored from the temporal dynamics of the ring vibration mode, which is less sensitive to solvation and hydrogen bonding. The present study provides insight into the specific and nonspecific solvation-controlled charge transfer dynamics in aprotic and protic solvents using FPe as a probe.

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Subpicosecond UV-pump and IR-probe Spectroscopy of 9-Fluorenone in Deuterated Acetonitrile and Methanol

Cited by 10 publications

References 10 publications

Ultrafast Dynamics of Hydrogen Bond Breaking and Making in the Excited State of Fluoren-9-one: Time-Resolved Visible Pump–IR Probe Spectroscopic Study

Ultrafast Dynamics of Hydrogen Bond Breaking and Making in the Excited State of Fluoren-9-one: Time-Resolved Visible Pump–IR Probe Spectroscopic Study

Vibrational dynamics of the CO stretching of 9-fluorenone studied by visible-pump and infrared-probe spectroscopy

Disentangling Time Scales of Vibrational Cooling, Solvation, and Hydrogen Bond Reorganization Dynamics Using Ultrafast Transient Infrared Spectroscopy of Formylperylene

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