Structure Set in Stone: Designing Rigid Linkers to Control the Efficiency of Intramolecular Singlet Fission

Ahrens, Lukas; Wollscheid, Nikolaus; Han, Jie; Kefer, Oskar; Röminger, Frank; Roozbeh, Ashkan; Freudenberg, Jan; Dreuw, Andreas; Bunz, Uwe H. F.; Buckup, Tiago

doi:10.1021/acs.jpcb.1c07122

Cited by 5 publications

(28 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several chromophores have been exploited to control structure and explore mechanistic aspects of i -SF, including examples such as perylenediimides, terylenediimides, − diphenylisobenzofurans, tetracenes, , azaacenes, and diketopyrrolopyrroles . The most versatile molecular systems to date, however, have been derivatives of pentacene, which fulfill the fundamental thermodynamic requirement for SF with singlet and triplet energies of ca.…”

Section: Introductionmentioning

confidence: 99%

Sensitized Singlet Fission in Rigidly Linked Axial and Peripheral Pentacene-Subphthalocyanine Conjugates

et al. 2023

View full text Add to dashboard Cite

The goal of harnessing the theoretical potential of singlet fission (SF), a process in which one singlet excited state is split into two triplet excited states, has become a central challenge in solar energy research. Covalently linked dimers provide crucial models for understanding the role of chromophore arrangement and coupling in SF. Sensitizers can be integrated into these systems to expand the absorption bandwidth through which SF can be accessed. Here, we define the role of the sensitizer-chromophore geometry in a sensitized SF model system. To this end, two conjugates have been synthesized consisting of a pentacene dimer (SF motif) connected via a rigid alkynyl bridge to a subphthalocyanine (the sensitizer motif) in either an axial or a peripheral arrangement. Steady-state and time-resolved photophysical measurements are used to confirm that both conjugates operate as per design, displaying near unity energy transfer efficiencies and high triplet quantum yields from SF. Decisively, energy transfer between the subphthalocyanine and pentacene dimer occurs ca. 26 times faster in the peripheral conjugate, even though the two chromophores are ca. 3 Å farther apart than in the axial conjugate. Following a theoretical evaluation of the dipolar coupling, V dip 2, and the orientation factor, κ2, of both the axial (V dip 2 = 140 cm–2; κ2 = 0.08) and the peripheral (V dip 2 = 724 cm–2; κ2 = 1.46) arrangements, we establish that this rate acceleration is due to a more favorable (nearly co-planar) relative orientation of the transition dipole moments of the subphthalocyanine and pentacenes in the peripheral constellation.

show abstract

Section: Introductionmentioning

confidence: 99%

Sensitized Singlet Fission in Rigidly Linked Axial and Peripheral Pentacene-Subphthalocyanine Conjugates

et al. 2023

View full text Add to dashboard Cite

show abstract

“…The successful introduction of the stilbene-type double bond was evident by the pale yellow color and blueish fluorescence of S3 in dilute solution under UV irradiation (see Supporting Information for absorption and emission spectra, Figure S2). The [6,8,9] and structures investigated herein. The secondary etheno-/ethano-bridge, connecting the two formal (aza)acene subunits, is highlighted in blue.…”

Section: Resultsmentioning

confidence: 99%

“…[5,6] Facile substitution, for example in the periphery [7] or via dimerization, [5d,e,6,8] tailors their optoelectronics and solid-state packing. Spiro-linked homodimers (such as A and B, Figure 1) [6,8,9] allow to study the intramolecular SF (iSF) process and may improve the performance of organic photovoltaics. [8,10] cis-Stilbenes photoisomerize, [11] forming either trans-stilbenes or, under oxidative conditions, phenanthrenes.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Etheno‐bridged Azaacene Spiro Dimers

Ahrens

Röminger

Freudenberg

et al. 2023

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

We present the synthesis of two sets of spiro‐connected azaacene dimers. Their geometry and electronic coupling are critically determined by a secondary linker, i. e., an etheno‐ and an ethano‐bridge. The core fragment of the etheno‐bridged dimer corresponds to a conformationally locked cis‐stilbene. Optoelectronic properties, single crystal X‐ray structures and stability with respect to oxidation of the conjugated and non‐conjugated dimers are reported and compared. The conjugated dimers exhibit smaller optical gaps and bathochromically shifted absorption maxima, but are prone to unexpected oxygen addition, dearomatizing one of the azaacene substituents.

show abstract

“…Intramolecular SFs (iSFs) in dilute solutions avoid intermolecular arrangements in films and diffusion collisions in concentrated solutions, and hence, only electronic and vibronic couplings of the involved states on SF sites are considered to declare the motivations in the iSF reactions. ,− Pentacene, with energy alignments E(S 1 ) > 2E(T 1 ), satisfies an exothermic demand of the SF, to be a unidirectional process . Pentacene dimers with near 200% iSF quantum yields (QYs) have been reported. , Spacer designations in the pentacene dimers with respect to conjugation/homoconjugation/nonconjugation and their rigid/flexible properties have been discussed on the formation and dissociation of 1 (T 1 T 1 ) and hence efficient iSF. ,,− With conjugated spacers, a fast transformation into 1 (T 1 T 1 ) combined with a fast annihilation is related to the direct mechanism. For nonconjugated spacers a slow SF rate with a long lifetime of the triplet pair may be driven by a CT related intermediate state.…”

Section: Introductionmentioning

confidence: 99%

Intramolecular Singlet Fission in Pentacene Oligomers via an Intermediate State

et al. 2023

View full text Add to dashboard Cite

Intramolecular singlet fission (iSF) is an efficient strategy of multiexciton generation via a singlet exciton splitting into a correlated triplet pair in one organic molecule with more than two chromophores. Propellershaped iptycene-linked triisopropylsilyl(TIPS)-ethynyl functionalized pentacene oligomers (pent-monomer, pent-dimer, and pent-trimer) were synthesized, and the iSF dynamics of pent-dimer and -trimer were monitored by a visible−near-IR transient absorption (TA) spectroscopy. Quantum yields of the triplet pair, ∼80%, of both estimated by near-IR TA spectral analysis are in good agreement with the results of global analysis and triplet sensitization experiments. The iSF rate of pent-trimer is slightly faster than that of pent-dimer even with one more chromophore site. The unexpectedly weak difference indicates the existence of an intermediate process to realize iSF. The intermediate process might be determined by through-bond electronic coupling of the homoconjugation bridge in the pentacene oligomers. Our results suggest the importance of the rigid bridge to the fast iSF rate and the elongated lifetime of the correlated triplet pair in pentacene oligomers.

show abstract

Structure Set in Stone: Designing Rigid Linkers to Control the Efficiency of Intramolecular Singlet Fission

Cited by 5 publications

References 64 publications

Sensitized Singlet Fission in Rigidly Linked Axial and Peripheral Pentacene-Subphthalocyanine Conjugates

Sensitized Singlet Fission in Rigidly Linked Axial and Peripheral Pentacene-Subphthalocyanine Conjugates

Etheno‐bridged Azaacene Spiro Dimers

Intramolecular Singlet Fission in Pentacene Oligomers via an Intermediate State

Contact Info

Product

Resources

About