Solvent assisted excited-state deactivation pathways in isolated 2,7-diazaindole-S1-3 (S = Water and Ammonia) complexes

Chowdhury, Prahlad Roy; Khodia, Saurabh; Maity, Surajit

doi:10.1016/j.saa.2022.121285

Cited by 7 publications

(12 citation statements)

References 44 publications

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“…A similar solvent-tochromophore excited state proton transfer was also reported for 2,7-diazaindole-(H 2 O) 1-3 complexes, and the energy barriers were calculated to be nearly similar to those of the respective concerted hydrogen atom transfer pathways. 27 The accurate description of solvent-to-chromophore proton transfer requires further experimental data. Based on the limited experimental data, it can be proposed that the ESPT process is highly dependent on the polarity of the hydrogen bond donor group of the solvent.…”

Section: Introductionmentioning

confidence: 99%

A combined spectroscopic and computational investigation on the solvent-to-chromophore excited-state proton transfer in the 2,2′-pyridylbenzimidazole–methanol complex

Jarupula

Khodia

Shabeeb

et al. 2023

Phys. Chem. Chem. Phys.

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Section: Introductionmentioning

confidence: 99%

A combined spectroscopic and computational investigation on the solvent-to-chromophore excited-state proton transfer in the 2,2′-pyridylbenzimidazole–methanol complex

Jarupula

Khodia

Shabeeb

et al. 2023

Phys. Chem. Chem. Phys.

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“…A detailed description of the calculation of ESPT and ESHT processes is given elsewhere. 16,33 In brief, the initial geometry of the proton transfer (PT) state of the PBI-S complex was generated by adding a hydroxide ion OH -(for PBI-H2O complex) and NH2 -(for PBI-NH3 complex) to the protonated PBI cation (PBIH + ) forming hydrogen-bond between the NH groups. Subsequently, the potential energy profiles (PES) were calculated for the ESPT and ESHT pathways by scanning the NP‧ ‧‧H bond length along the proton-transfer and hydrogen transfer, respectively.…”

Section: Methodsmentioning

confidence: 99%

Excited State Deactivation via Solvent to Chromophore Proton Transfer in Isolated 1:1 Molecular Complex: Experimental Validation by Measuring the Energy Barrier and Kinetic Isotope Effect

Khodia¹,

Jarupula²,

Baweja³

et al. 2023

Preprint

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We have experimentally demonstrated conclusive evidence of solvent-to-chromophore excited state proton transfer (ESPT) as a deactivation mechanism in a binary complex isolated in the gas phase. The above was achieved by determining the energy barrier of the ESPT processes, qualitatively analysing the quantum tunnelling rates and evaluating the kinetic isotope effect. The 1:1 complexes of 2,2’-pyridylbenzimidazole (PBI) with H2O, D2O and NH3, produced in a supersonic jet-cooled molecular beam, were characterised spectroscopically. The vibrational frequencies of the complexes in the S1 electronic state were recorded using a resonant two-colour two-photon ionization method coupled to a Time-ofFlight mass spectrometer set-up. In the PBI-H2O, the ESPT energy barrier of 43110 cm-1 was measured using UV-UV hole-burning spectroscopy. The exact reaction pathway was experimentally determined by isotopic substitution of the tunnelling proton (in PBI-D2O) and increasing the width of the proton transfer barrier (in PBI-NH3). In both cases, the energy barrier was significantly increased to > 1030 cm-1 in the PBI-D2O and to > 868 cm-1 in PBI-NH3. The heavy atom in PBI-D2O decreased the zero-point energy in the S1 state significantly, resulting in the elevation of the energy barrier. Secondly, the solvent-to-chromophore proton tunnelling was found to decrease drastically upon deuterium substitution. In the PBI-NH3 complex, the solvent molecule formed a preferential hydrogen bonding with the acidic (PBI)N-H group. This led to the formation of a weak hydrogen bonding between the ammonia and the pyridyl-N atom, thus, increasing the proton transfer barrier width (H2NH‧‧‧Npyridyl(PBI)). The above resulted in increased barrier height and decreased quantum tunnelling rate in the excited state. The experimental investigation, aided by computational investigations, demonstrated conclusive evidence of a novel deactivation channel of an electronically excited biologically relevant system. The variation observed for the energy barrier and the quantum tunnelling rate by substituting NH3 in place of H2O can be directly correlated to the drastically different photochemical and photo-physical reactions of biomolecules under various microenvironments.

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“…A detailed description of the calculation of ESPT and ESHT processes is given elsewhere. 16,33 In brief, the initial geometry of the proton transfer (PT) state of the PBI-S complex was generated by adding a hydroxide ion OH À (for the PBI-H 2 O complex) and NH 2 À (for the PBI-NH 3 complex) to the protonated PBI cation (PBIH + ), forming a hydrogen-bond between the NH groups. Subsequently, the potential energy surface (PES) profiles were calculated for the ESPT and ESHT pathways by scanning the N P Á Á ÁH bond length along the proton transfer and hydrogen transfer coordinates, respectively.…”

Section: Computationalmentioning

confidence: 99%

Excited-state deactivation via solvent-to-chromophore proton transfer in an isolated 1 : 1 molecular complex: experimental validation by measuring the energy barrier and kinetic isotope effect

Khodia

Jarupula

Baweja

et al. 2023

Phys. Chem. Chem. Phys.

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Solvent assisted excited-state deactivation pathways in isolated 2,7-diazaindole-S1-3 (S = Water and Ammonia) complexes

Cited by 7 publications

References 44 publications

A combined spectroscopic and computational investigation on the solvent-to-chromophore excited-state proton transfer in the 2,2′-pyridylbenzimidazole–methanol complex

A combined spectroscopic and computational investigation on the solvent-to-chromophore excited-state proton transfer in the 2,2′-pyridylbenzimidazole–methanol complex

Excited State Deactivation via Solvent to Chromophore Proton Transfer in Isolated 1:1 Molecular Complex: Experimental Validation by Measuring the Energy Barrier and Kinetic Isotope Effect

Excited-state deactivation via solvent-to-chromophore proton transfer in an isolated 1 : 1 molecular complex: experimental validation by measuring the energy barrier and kinetic isotope effect

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