Triplet-triplet interactions between dimers of a copper maleonitriledithiolate complex

Snaathorst, D.; Keijzers, C. P.

doi:10.1080/00268978400100351

Cited by 6 publications

(5 citation statements)

References 9 publications

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“…), while the asymmetric 3 (TT) 0 states remain as pure triplets. [48,50] As such, the iSF generated triplet pair tr-ESR spectra will be dominated by absorption/emission from TT MHz and a directional spin-spin coupling of = MHz the 1 (TT) 0 and 5 (TT) -2 states mix within the field range of our experiment; this allows for an additional absorptive transition to be simulated (blue dashed line) and an excellent fit of the data. The dominance of isotropic (TT) exchange coupling over anisotropic spin-spin coupling is indicative of a through-space interaction rather than a dipole-dipole interaction.…”

Section: Identifying Isf Spin States With Electron Spin Resonancementioning

confidence: 84%

“…[47] Given the separation between the two pentacenes is ~16Å, we expect the spin-spin dipole-dipole interaction component, X, to be on the order of 10 MHz. [48] The positive isotropic coupling gives rise to a ~80µeV splitting between the singlet and quintet manifolds [50] and the peaks of the TT ! !…”

Section: Identifying Isf Spin States With Electron Spin Resonancementioning

confidence: 99%

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Quintet multiexciton dynamics in singlet fission

et al. 2016

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Singlet fission (SF), in which two triplet excitons are generated from a single absorbed photon, is a key third generation solar cell concept. Conservation of angular momentum requires that SF populates correlated multiexciton states, which can subsequently dissociate to generate free triplets. However, little is known about electronic and spin correlations in these systems since, due to its typically short lifetime, the multiexciton state is challenging to isolate and study. Here, we use bridged pentacene dimers, which undergo intramolecular SF while isolated in solution and in solid matrices, as a unimolecular model system that can trap long-lived multiexciton states. We combine transient absorption and time-resolved electron spin resonance (ESR) spectroscopy to show that spin correlations in the multiexciton state persist for 100s of nanoseconds. Furthermore, we confirm longstanding predictions that SF produces triplet pair states (TT) of quintet character -the first direct observation of quintet states in closed shell organic molecules. We compare two different pentacene-bridge-pentacene chromophores, systematically tuning the coupling between the pentacenes to understand how differences in molecular structure affect the population and dissociation of multiexciton quintet states.

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Section: Identifying Isf Spin States With Electron Spin Resonancementioning

confidence: 84%

Section: Identifying Isf Spin States With Electron Spin Resonancementioning

confidence: 99%

Quintet multiexciton dynamics in singlet fission

et al. 2016

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“…In the absence of nonadiabatic coupling and geometric molecular reorganization, the fine structure of four-electron states is described by the total spin Hamiltonian. This is shown below for four electrons at sites A and B in the absence of spin-orbit coupling (32)(33)(34)(35):…”

Section: Fine Structure Of the Lowest-lying Four-electron Statesmentioning

confidence: 98%

“…The fine-structure splitting between sublevels and stabilization relative to 2E T is likely to be more complex than that described here. It will include, for example, mixing between |S 1 and |S (2) 1 that should stabilize |S 1 relative to |T 1 and |Q , and mixing with different charge-transfer states (34). [We recall that throughout |S 1 denotes the four-electron singlet (S = 0), while |S (2) 1 denotes the two-electron singlet.]…”

Section: Fine Structure Of the Lowest-lying Four-electron Statesmentioning

confidence: 99%

“…• D inter • ŜB can be formulated in different ways, depending on how the intertriplet geometry and exchange interactions are accounted for(32)(33)(34)(35); and it can be approximated to D AB ( ŜA,z ŜB,z − ŜA ŜB /3)(32), where D AB is the intertriplet dipolar coupling, and the spin operators are given by ŜA = Ŝ1 + Ŝ2 and ŜB = Ŝ3 + Ŝ4 . In molecular systems such as tetracene, recent measurements suggest that the intertriplet D AB is approximately 10 neV(21,33), compared with intratriplet D i ∼ 10 μeV.…”

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confidence: 99%

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Triplet-Pair States in Organic Semiconductors

Musser

Clark

2019

Annu. Rev. Phys. Chem.

132

180

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Entanglement of states is one of the most surprising and counterintuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic semiconductor materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which consists of a pair of localized triplet excitons coupled into an overall spin-0, -1, or -2 configuration. The most widely analyzed of these is the spin-0 pair, denoted1(TT), which was initially invoked in the 1960s to explain delayed fluorescence in acene films. It is considered an essential gateway state for triplet-triplet annihilation and the reverse process, singlet fission, enabling interconversion between one singlet and two triplet excitons without any change in overall spin. This state has returned to the forefront of organic materials research in recent years, thanks both to its central role in the resurgent field of singlet fission and to its implication in a host of exotic new photophysical behaviors. Here we review the properties of triplet-pair states, from first principles to recent experimental results.

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Selected Examples of Spectra of Pairs

Bencini

Gatteschi

1990

Electron Paramagnetic Resonance of Exchange Coupled Systems

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Very detailed EPR spectra have been recorded for manganese (II) pairs in MgO and CaO. Manganese(II) enters substitutionally the host crystals: at concentrations of about 1 % appreciable numbers of isolated pairs are found which were characterized at three frequencies (15.5, 24.5, and 35.5 GHz) over the temperature range 1.2 to 300 K [7.1].A typical spectrum of Mn2+: CaO at 35.5 GHz is shown in Fig. 7.1. Signals are observed from all the five total spin states: it is apparent that on lowering temperature the low spin states increase the intensity relative to the high spin states. The signals shown in Fig. 7.1 are only part of the spectrum, the scheme of which is given in Fig. 7.2. The temperature dependence of the signal intensity of Mn:MgO was found to conform to the curves of Fig. 3.3, and the order of the levels is shown in Fig. 7.3. The levels deviate considerably from a Lande interval rule (Table 7.1), a result which was explained by including biquadratic terms. The levels on the left in Fig. 7.3 are calculated only with bilinear exchange, while those on the right, which correspond to a good approximation of the experimental data, are obtained including a biquadratic exchange constant j, such that j/J =0.05. The effect of biquadratic exchange on the energy separations is quite dramatic, according to the relation:The biquadratic term may have its origin from both an intrinsic higher order exchange and by exchange striction as discussed in Section 2.4. Beyond the departure from Lande interval rule biquadratic exchange has been considered to be responsible also for the departure of the anisotropic exchange parameters from the simple behavior expected using Eq. (3.21).

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Triplet-triplet interactions between dimers of a copper maleonitriledithiolate complex

Cited by 6 publications

References 9 publications

Quintet multiexciton dynamics in singlet fission

Quintet multiexciton dynamics in singlet fission

Triplet-Pair States in Organic Semiconductors

Selected Examples of Spectra of Pairs

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