Intermolecular Hydrogen Bonding Tunes Vibronic Coupling in Heptazine Complexes
| Autor: | Cody W. Schlenker, Emily J. Rabe, Doyk Hwang, Harrison J. Goldwyn, David J. Masiello |
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| Rok vydání: | 2020 |
| Předmět: |
Materials science
010304 chemical physics Heptazine Hydrogen bond Intermolecular force 010402 general chemistry 01 natural sciences Molecular electronic transition 0104 chemical sciences Surfaces Coatings and Films Electron transfer chemistry.chemical_compound Vibronic coupling chemistry Chemical physics Molecular vibration Excited state 0103 physical sciences Materials Chemistry Physical and Theoretical Chemistry |
| Zdroj: | The Journal of Physical Chemistry B. 124:11680-11689 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/acs.jpcb.0c07719 |
| Popis: | To better understand how hydrogen bonding influences the excited-state landscapes of aza-aromatic materials, we studied hydrogen-bonded complexes of 2,5,8-tris (4-methoxyphenyl)-1,3,4,6,7,9,9b-heptaazaphenalene (TAHz), a molecular photocatalyst related to graphitic carbon nitride, with a variety of phenol derivatives (R-PhOH). By varying the electron-withdrawing character of the para-substituent on the phenol, we can modulate the strength of the hydrogen bond. Using time-resolved photoluminescence, we extract a spectral component associated with the R-PhOH-TAHz hydrogen-bonded complex. Surprisingly, we noticed a striking change in the relative amplitude of vibronic peaks in the TAHz-centered emission as a function of R-group on phenol. To gain a physical understanding of these spectral changes, we employed a displaced-oscillator model of molecular emission to fit these spectra. This fit assumes that two vibrational modes are dominantly coupled to the emissive electronic transition and extracts their frequencies and relative nuclear displacements (related to the Huang-Rhys factor). With the aid of quantum chemical calculations, we found that heptazine ring-breathing and ring-puckering modes are likely responsible for the observed vibronic progression, and both modes indicate decreasing molecular distortion in the excited state with increasing hydrogen bond strength. This finding offers new insights into intermolecular excited-state hydrogen bonding, which is a crucial step toward controlling excited-state proton-coupled electron transfer and proton transfer reactions. |
| Databáze: | OpenAIRE |
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