Higher-energy triplet-pair states in polyenes and their role in intramolecular singlet fission

Valentine, D. J.; Manawadu, Dilhan; Barford, William

doi:10.1103/physrevb.102.125107

Cited by 19 publications

(63 citation statements)

References 54 publications

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“…In particular, it was shown in Ref. 14 that for all chain lengths the vertical and relaxed 2 1 A − g energies lie below the corresponding 1 1 B + u energies. In contrast, while the 1 1 B − u relaxed energy is lower than the 1 1 B + u relaxed energy, its vertical energy is higher than the 1 1 B + u vertical energy for N < 22 C-atoms.…”

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confidence: 90%

“…In understanding the process of singlet fission, it is useful to recall how a pair of triplets combine, 12,13 namely T 1 ⊗ T 1 = S + T + Q, where T 1 represents the lowest-energy triplet, and S, T and Q are the singlet, triplet and quintet 'correlated triplet-pair' states, respectively. Using the density matrix renormalization group (DMRG) method to solve the Pariser-Parr-Pople-Peierls (PPPP) model of π-conjugated systems, Valentine et al 14 performed an extensive theoretical and computational study of the triplet-pair states of polyene chains. They showed that the singlet triplet-pair state forms a band of states,…”

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confidence: 99%

“…Since the UV model does not contain the long-range Coulomb terms of the PPP model, as described in the SI it is necessary to parametrize U and V to reproduce the predictions of Ref. 14 The electrons couple to the nuclei via changes in the C-C bond length, specifically via…”

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confidence: 99%

“…Here we adopt the particle-hole notation used in Ref.,14 which is typically used by the experimental community. It is the opposite definition to that used in Ref 5,19.…”

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confidence: 99%

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Singlet Triplet-Pair Production and Possible Singlet-Fission in Carotenoids

Manawadu¹,

Valentine²,

Marcus³

et al. 2021

Preprint

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Internal conversion from the photoexcited state to a correlated singlet triplet-pair state is believed to be the precursor of singlet fission in carotenoids. We present numerical simulations of this process using a π-electron model that fully accounts for electron-electron interactions and electron-nuclear coupling. The time-evolution of the electrons is determined rigorously using the time-dependent density matrix renormalization method, while the nuclei are evolved via the Ehrenfest equations of motion. We apply this to zeaxanthin, a carotenoid chain with 22 conjugated carbon atoms (i.e., 11 double bonds). We show that the internal conversion of the photoexcited state to the singlet triplet-pair state occurs adiabatically via an avoided crossing within 100 fs and we predict a yield of ∼ 50% We further discuss whether this singlet tripletpair state will undergo exothermic versus endothermic intra or inter chain singlet fission.

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confidence: 90%

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confidence: 99%

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confidence: 99%

“…Here we adopt the particle-hole notation used in Ref.,14 which is typically used by the experimental community. It is the opposite definition to that used in Ref 5,19.…”

mentioning

confidence: 99%

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Singlet Triplet-Pair Production and Possible Singlet-Fission in Carotenoids

Manawadu¹,

Valentine²,

Marcus³

et al. 2021

Preprint

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“…Candidate states are the 2 1 A − g (S 1 ) state, and the slightly higher in energy 1 1 B − u and 3 1 A − g states. Recent theoretical modelling by Valentine, Manawadu and Barford [16] of the Pariser-Parr-Pople-Peierls model of π-conjugated electrons has identified the 3 1 A − g state as a viable candidate for this intermediate state. As shown in [16], the 3 1 A − g state corresponds to a pair of unbound triplets (in contrast to the 2 1 A − g state, which is described as a pair of bound triplet states [17][18][19][20]).…”

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confidence: 99%

Triplet-Triplet Decoherence in Singlet Fission

Marcus,

Barford

2020

Preprint

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Singlet fission is commonly defined to involve a process by which an overall singlet state with local triplet structure spin-decoheres into two triplet states, thereby completing the fission process. This process, often defined in loose terms involving the multiplicity of the overall state, is investigated here using a uniform Heisenberg spin-chain subject to a dephasing environmental interaction. We introduce new results from quantum information theory which enables the quantification of coherence and entanglement in a bi-and multipartite system. The calculated measures of these quantum effects can be linked to observables, such as magnetisation and total spin, with simulations of the model and using theoretical methods. We demonstrate that these observables can act as a proxy for the coherence and entanglement measures. The decay of both of these between the two local triplets can be monitored, enabling a clear definition of the spin-decoherence process in singlet fission.

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Shining Light on Inverted Singlet–Triplet Emitters

Bedogni,

Giavazzi,

Di Maiolo

et al. 2023

J. Chem. Theory Comput.

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The inversion of the lowest singlet and triplet excited states, observed in several triangle-shaped organic molecules containing conjugated carbon and nitrogen atoms, is an astonishing result that implies the breakdown of Hund's rule. The phenomenon attracted interest for its potential toward triplet harvesting in organic LEDs. On a more fundamental vein, the singlet−triplet (ST) inversion sheds new light on the role of electron correlations in the excited-state landscape of π-conjugated molecules. Relying on the celebrated Pariser−Parr−Pople model, the simplest model for correlated electrons in π-conjugated systems, we demonstrate that the ST inversion does not require triangle-shaped molecules nor any specific molecular symmetry. Indeed, the ST inversion does not require strictly non-overlapping HOMO and LUMO orbitals but rather a small gap and a small exchange integral between the frontier orbitals.

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Higher-energy triplet-pair states in polyenes and their role in intramolecular singlet fission

Cited by 19 publications

References 54 publications

Singlet Triplet-Pair Production and Possible Singlet-Fission in Carotenoids

Singlet Triplet-Pair Production and Possible Singlet-Fission in Carotenoids

Triplet-Triplet Decoherence in Singlet Fission

Shining Light on Inverted Singlet–Triplet Emitters

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