Excitation-Energy Transfer and Vibronic Relaxation through Light-Harvesting Dendrimer Building Blocks: a Nonadiabatic Perspective
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| Format: | Preprint |
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2024
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| _version_ | 1866916156579774464 |
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| author | Galiana, Joachim Lasorne, Benjamin |
| author_facet | Galiana, Joachim Lasorne, Benjamin |
| contents | The light-harvesting excitonic properties of poly(phenylene ethynylene) (PPE) extended dendrimers (tree-like π-conjugated macromolecules) involve a directional cascade of local excitation-energy transfer (EET) processes occurring from the "leaves" (shortest branches) to the "trunk" (longest branch), which can be viewed from a vibronic perspective as a sequence of internal conversions occurring among a connected graph of nonadiabatically coupled locally-excited (LE) electronic states via conical intersections. The smallest PPE building block able to exhibit EET, the asymmetrically meta-substituted PPE oligomer with one acetylenic bond on one side and two parallel ones on the other side (2-ring and 3-ring para-substituted pseudo-fragments), is a prototype and the focus of the present work. From time-dependent density-functional theory (TD-DFT) electronic-structure calculations of the molecule as regards its first two nonadiabatically coupled, optically active, singlet excited states, we built a (1+2)-state-8-dimensional vibronic-coupling Hamiltonian (VCH) model for running multiconfiguration time-dependent Hartree (MCTDH) wavepacket relaxations and propagations, yielding both steady-state absorption and emission spectra, as well as real-time dynamics. The EET process from the shortest branch to the longest one occurs quite efficiently (about 80% quantum yield) within the first 25 fs after light excitation and is mediated vibrationally through acetylenic and quinoidal bond-stretching modes together with a particular role given to the central-ring anti-quinoidal rock-bending mode. Electronic and vibrational energy relaxations, together with redistributions of quantum populations and coherences, are interpreted through the lens of a nonadiabatic perspective, showing some interesting segregation among the foremost photoactive degrees of freedom as regards spectroscopy and reactivity. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2401_01790 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Excitation-Energy Transfer and Vibronic Relaxation through Light-Harvesting Dendrimer Building Blocks: a Nonadiabatic Perspective Galiana, Joachim Lasorne, Benjamin Chemical Physics The light-harvesting excitonic properties of poly(phenylene ethynylene) (PPE) extended dendrimers (tree-like π-conjugated macromolecules) involve a directional cascade of local excitation-energy transfer (EET) processes occurring from the "leaves" (shortest branches) to the "trunk" (longest branch), which can be viewed from a vibronic perspective as a sequence of internal conversions occurring among a connected graph of nonadiabatically coupled locally-excited (LE) electronic states via conical intersections. The smallest PPE building block able to exhibit EET, the asymmetrically meta-substituted PPE oligomer with one acetylenic bond on one side and two parallel ones on the other side (2-ring and 3-ring para-substituted pseudo-fragments), is a prototype and the focus of the present work. From time-dependent density-functional theory (TD-DFT) electronic-structure calculations of the molecule as regards its first two nonadiabatically coupled, optically active, singlet excited states, we built a (1+2)-state-8-dimensional vibronic-coupling Hamiltonian (VCH) model for running multiconfiguration time-dependent Hartree (MCTDH) wavepacket relaxations and propagations, yielding both steady-state absorption and emission spectra, as well as real-time dynamics. The EET process from the shortest branch to the longest one occurs quite efficiently (about 80% quantum yield) within the first 25 fs after light excitation and is mediated vibrationally through acetylenic and quinoidal bond-stretching modes together with a particular role given to the central-ring anti-quinoidal rock-bending mode. Electronic and vibrational energy relaxations, together with redistributions of quantum populations and coherences, are interpreted through the lens of a nonadiabatic perspective, showing some interesting segregation among the foremost photoactive degrees of freedom as regards spectroscopy and reactivity. |
| title | Excitation-Energy Transfer and Vibronic Relaxation through Light-Harvesting Dendrimer Building Blocks: a Nonadiabatic Perspective |
| topic | Chemical Physics |
| url | https://arxiv.org/abs/2401.01790 |