Strong Duschinsky Mixing Induced Breakdown of Kasha's Rule in an Organic Phosphor

Lopa Paul, Torsha Moitra, Kenneth Ruud*, Swapan Chakrabarti

*Corresponding author for this work

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Abstract

We present the novel observation that Duschinsky mixings can lead to the breakdown of Kasha's rule in a white light phosphor molecule, Dibenzo[b,d]thiophen-2-yl (4-chlorophenyl)methanone. Our theoretical analyses show the energy gap between the T1 and T2 states (0.48 eV) is too large to allow for any significant population of the T2 state at room temperature and instead the faster intersystem crossing (ISC) between the S1 and T2 states is rather due to strong Duschinsky mixing induced, leading to the emission from the T2 state as well. A second-order cumulant-based method has been used for the calculation of the ISC rate, which suggests two order of magnitudes faster ISC rates for S1→T2 compared to S1→T1. We found that the carbonyl moiety of the S1 and T2 states of the molecule is significantly different with respect to bond angle and dihedral angles, engendering large displacements in selective normal modes, thus giving rise to strong Duschinsky mixing.
Original languageEnglish
JournalJournal of Physical Chemistry Letters
Volume10
Issue number3
Pages (from-to)369-374
Number of pages6
ISSN1948-7185
DOIs
Publication statusPublished - 2019

Cite this

Paul, Lopa ; Moitra, Torsha ; Ruud, Kenneth ; Chakrabarti, Swapan. / Strong Duschinsky Mixing Induced Breakdown of Kasha's Rule in an Organic Phosphor. In: Journal of Physical Chemistry Letters. 2019 ; Vol. 10, No. 3. pp. 369-374.
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title = "Strong Duschinsky Mixing Induced Breakdown of Kasha's Rule in an Organic Phosphor",
abstract = "We present the novel observation that Duschinsky mixings can lead to the breakdown of Kasha's rule in a white light phosphor molecule, Dibenzo[b,d]thiophen-2-yl (4-chlorophenyl)methanone. Our theoretical analyses show the energy gap between the T1 and T2 states (0.48 eV) is too large to allow for any significant population of the T2 state at room temperature and instead the faster intersystem crossing (ISC) between the S1 and T2 states is rather due to strong Duschinsky mixing induced, leading to the emission from the T2 state as well. A second-order cumulant-based method has been used for the calculation of the ISC rate, which suggests two order of magnitudes faster ISC rates for S1→T2 compared to S1→T1. We found that the carbonyl moiety of the S1 and T2 states of the molecule is significantly different with respect to bond angle and dihedral angles, engendering large displacements in selective normal modes, thus giving rise to strong Duschinsky mixing.",
author = "Lopa Paul and Torsha Moitra and Kenneth Ruud and Swapan Chakrabarti",
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doi = "10.1021/acs.jpclett.8b03624",
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journal = "The Journal of Physical Chemistry Letters",
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Strong Duschinsky Mixing Induced Breakdown of Kasha's Rule in an Organic Phosphor. / Paul, Lopa; Moitra, Torsha; Ruud, Kenneth; Chakrabarti, Swapan.

In: Journal of Physical Chemistry Letters, Vol. 10, No. 3, 2019, p. 369-374.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Strong Duschinsky Mixing Induced Breakdown of Kasha's Rule in an Organic Phosphor

AU - Paul, Lopa

AU - Moitra, Torsha

AU - Ruud, Kenneth

AU - Chakrabarti, Swapan

PY - 2019

Y1 - 2019

N2 - We present the novel observation that Duschinsky mixings can lead to the breakdown of Kasha's rule in a white light phosphor molecule, Dibenzo[b,d]thiophen-2-yl (4-chlorophenyl)methanone. Our theoretical analyses show the energy gap between the T1 and T2 states (0.48 eV) is too large to allow for any significant population of the T2 state at room temperature and instead the faster intersystem crossing (ISC) between the S1 and T2 states is rather due to strong Duschinsky mixing induced, leading to the emission from the T2 state as well. A second-order cumulant-based method has been used for the calculation of the ISC rate, which suggests two order of magnitudes faster ISC rates for S1→T2 compared to S1→T1. We found that the carbonyl moiety of the S1 and T2 states of the molecule is significantly different with respect to bond angle and dihedral angles, engendering large displacements in selective normal modes, thus giving rise to strong Duschinsky mixing.

AB - We present the novel observation that Duschinsky mixings can lead to the breakdown of Kasha's rule in a white light phosphor molecule, Dibenzo[b,d]thiophen-2-yl (4-chlorophenyl)methanone. Our theoretical analyses show the energy gap between the T1 and T2 states (0.48 eV) is too large to allow for any significant population of the T2 state at room temperature and instead the faster intersystem crossing (ISC) between the S1 and T2 states is rather due to strong Duschinsky mixing induced, leading to the emission from the T2 state as well. A second-order cumulant-based method has been used for the calculation of the ISC rate, which suggests two order of magnitudes faster ISC rates for S1→T2 compared to S1→T1. We found that the carbonyl moiety of the S1 and T2 states of the molecule is significantly different with respect to bond angle and dihedral angles, engendering large displacements in selective normal modes, thus giving rise to strong Duschinsky mixing.

U2 - 10.1021/acs.jpclett.8b03624

DO - 10.1021/acs.jpclett.8b03624

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VL - 10

SP - 369

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JO - The Journal of Physical Chemistry Letters

JF - The Journal of Physical Chemistry Letters

SN - 1948-7185

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