Acceptor Dyads Research Articles

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence.

In order to investigate the joint influence of the conformation flexibility and the matching of the energies of the charge-transfer (CT) and the localized triplet excited (3LE) states on the thermally activated delayed fluorescence (TADF) in electron donor–acceptor molecules, a series of compact electron donor–acceptor dyads and a triad were prepared, with naphthalimide (NI) as electron acceptor and phenothiazine (PTZ) as electron donor. The NI and PTZ moieties are either directly connected at the 3-position of NI and the N-position of the PTZ moiety via a C–N single bond, or they are linked through a phenyl group. The tuning of the energy order of the CT and LE states is achieved by oxidation of the PTZ unit into the corresponding sulfoxide, whereas conformation restriction is imposed by introducing ortho-methyl substituents on the phenyl linker, so that the coupling magnitude between the CT and the 3LE states can be controlled. The singlet oxygen quantum yield (ΦΔ) of NI-PTZ is moderate in n-hexane (HEX, ΦΔ = 19%). TADF was observed for the dyads, the biexponential luminescence lifetime are 16.0 ns (99.9%)/14.4 μs (0.1%) for the dyad and 7.2 ns (99.6%)/2.0 μs (0.4%) for the triad. Triplet state was observed in the nanosecond transient absorption spectra with lifetimes in the 4–48 μs range. Computational investigations show that the orthogonal electron donor–acceptor molecular structure is beneficial for TADF. These calculations indicate small energetic difference between the 3LE and 3CT states, which are helpful for interpreting the ns-TA spectra and the origins of TADF in NI-PTZ, which is ultimately due to the small energetic difference between the 3LE and 3CT states. Conversely, NI-PTZ-O, which has a higher CT state and bears a much more stabilized 3LE state, does not show TADF.

Charge Separation/Recombination, Intersystem Crossing, and Unusually Slow Intramolecular Triplet-Triplet Energy Transfer in Naphthalenediimide-Anthracene Compact Energy Donor-Acceptor Dyads.

Three anthracene (An)-naphthalenediimide (NDI) compact electron donor-acceptor dyads were prepared. Femtosecond transient absorption (fs-TA) spectra show fast charge separation (ca. 0.9-1.7 ps) and relatively slow charge recombination (ca. 8-565 ps) upon photoexcitation; moreover, the 3An state was observed for 9-An-NDI, whereas the final state is 3NDI for both 9-An-Ph-NDI and 2-An-Ph-NDI, which have an intervening phenyl linker between the An and NDI units. Nanosecond transient absorption (ns-TA) spectra indicate that the lowest triplet state of all the dyads is 3An, with triplet lifetimes of 139-354 μs. An unusually slow intramolecular triplet-triplet energy transfer (TTET) was observed for 9-An-Ph-NDI and 2-An-Ph-NDI (32-85 ns). Time-resolved electron paramagnetic resonance (TREPR) spectroscopy confirms that the intersystem crossing (ISC) mechanism is spin orbit charge transfer ISC (SOCT-ISC) for all the dyads; for 9-An-NDI, only the 3An state was observed, while for the other two dyads, both 3NDI and 3An states were observed, with their relative population changing with increasing delay time, which supports TTET.

Frontispiz: Long‐Lived Charge‐Transfer State in Spiro Compact Electron Donor–Acceptor Dyads Based on Pyromellitimide‐Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization

Elektronentransfer. In ihrem Forschungsartikel (e202203758) untersuchen Jianzhang Zhao et al. den langlebigen Ladungstransferzustand in Spiro-Donor-Akzeptor-Dyaden auf der Grundlage von Pyromellitimid-abgeleitetem Rhodamin.

Frontispiece: Long‐Lived Charge‐Transfer State in Spiro Compact Electron Donor–Acceptor Dyads Based on Pyromellitimide‐Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization

Frontispiece: Long‐Lived Charge‐Transfer State in Spiro Compact Electron Donor–Acceptor Dyads Based on Pyromellitimide‐Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization

A coumarin coupled electron donor-acceptor dyad for cascade detection of aluminium ions and explosive nitroaromatic compounds

A coumarin coupled electron donor–acceptor dyad (HL) has been synthesized and characterized by different conventional techniques. Details spectroscopic investigation has been carried out to understand the photophysical behavior of as-prepared HL. The UV–visible spectral behavior of HL is found to be intramolecular charge transfer in nature and shows broadband, having maxima at 432 nm with a shoulder peak around 348 nm in DMF. The emission spectrum of HL also gives broadband, having maxima located at 480 nm in DMF. Further, HL is employed for the cascade detection of Al3+ ions (ON) and picric acid (PA, OFF) in DMF-H2O (7:3, v/v) media. A colorimetric change from yellow to colorless is observed in the presence of Al3+ ions. A significant fluorescence enhancement is observed due to the well coordination of Al3+ ions with HL. A visual bluish-green color could be seen under 365 nm UV light irradiation, which is also well supported by the color chromaticity diagram. The fluorescence of the HL-Al3+ complex is quenched in the presence of PA among all the tested nitroaromatic compounds. The sensitivity of HL and HL-Al3+ complex towards detection of Al3+ ions and PA can be possible down to 0.638 μM and 0.623 µM, respectively. The developed chemosensor is employed for the practical application for mapping Al3+ ions in the living cell. The performance of HL toward Al3+ ions proved that it could be exploited as a signal tool for environmental and biological samples.

Understanding High Fluorescence Quantum Yield and Simultaneous Large Stokes Shift in Phenyl Bridged Donor-π-Acceptor Dyads with Varied Bridge Lengths in Polar Solvents.

Photophysical properties of electron donor-π-acceptor (D-π-A) dyads for a given pair of D and A highly depend on the π-bridge type and length and also on the solvent polarity. In this work, first-principles calculations with optimally tuned range-separated hybrids are implemented to explore and understand the optical absorption and emission properties of recently synthesized novel D-π-A dyads with 1,2-diphenylphenanthroimidazole (PPI) as D and 1,2,4-triazolopyridine (TP) as A with varied phenyl π-bridge lengths (denoted as PPI-Pn-TP, n = 0-2 considered here) in solvents of different dielectrics. All three D-π-A dyads display almost an unaltered low-lying optical peak position and a red-shifted emission with increasing solvent polarity, corroborating well with the reported experimental observations. The observed emission shift was attributed to the stabilization of an intramolecular charge-transfer (ICT) state by the polar solvent. Contrastingly, our calculations reveal no ICT; rather the shift is essentially originated from the substantial excited-state relaxation involving primarily rotation of the PPI phenyl ring directly linked to the π-bridge, leading to an almost planarized emissive state. Further, the greater frontier molecular orbital delocalization-driven high fluorescence rate together with increased structural rigidity of the emissive state rationalize the observed high fluorescence quantum yield. The present research findings not only are helpful to better understand the reported experimental observations but also show routes to molecularly design functional D-π-A molecules for advanced optoelectronic, sensing, and biomedical applications.

Naphthalimide-Carbazole Compact Electron Donor-Acceptor Dyads: Effect of Molecular Geometry and Electron-Donating Capacity on the Spin-Orbit Charge Transfer Intersystem Crossing.

We prepared a series of naphthalimide (NI)-carbazole (Cz) compact electron donor-acceptor dyads showing different substitution positions, C-N/C-C linkers, and conformation restriction magnitudes to study the spin-orbit charge transfer intersystem crossing (SOCT-ISC). The varied conformation restrictions lead to different dihedral angles between the donor and acceptor (37°-81°) and electronic coupling magnitude (matrix elements V: 1290-3070 cm-1). Based on the comparison between the dyads containing C-N and C-C linkers, we found that a large dihedral angle between the donor and acceptor is favorable to efficient SOCT-ISC. For one dyad, the singlet oxygen quantum yield (ΦΔ) is up to 84.4% (in dichloromethane), which is much higher than that of the previously reported NI-phenothiazine (PTZ) analogue dyad (ΦΔ = 16.0% in n-hexane). The intrinsic triplet state lifetime (τT) is 270 μs, longer than that accessed by the heavy atom effect (75.2 μs). As compared with the NI-PTZ analogue dyad, the Cz unit in the current dyads is a weaker electron donor than PTZ. Thus, a higher CT state energy in NI-Cz dyads was observed, which makes the SOCT-ISC efficient in solvents with a wide range of polarities. Meanwhile, the localized triplet state (3LE) becomes the lowest-lying state in the NI-Cz dyads, which is different from the triplet charge transfer (3CT) state observed in the analogue NI-PTZ dyad. Moreover, the large energy gap between the CT and 3LE states inhibits the reverse ISC; as a result, no thermally activated delayed fluorescence was observed for the current NI-Cz dyads.

Red Light-Emitting Thermally-Activated Delayed Fluorescence of Naphthalimide-Phenoxazine Electron Donor-Acceptor Dyad: Time-Resolved Optical and Magnetic Spectroscopic Studies.

We prepared an orthogonal compact electron-donor (phenoxazine, PXZ)-acceptor (naphthalimide, NI) dyad (NI-PXZ), to study the photophysics of the thermally-activated delayed fluorescence (TADF), which has a luminescence lifetime of 16.4 ns (99.2 %)/17.0 μs (0.80 %). A weak charge transfer (CT) absorption band was observed for the dyad, indicating non-negligible electronic coupling between the donor and acceptor at the ground state. Femtosecond transient absorption spectroscopy shows a fast charge separation (CS) (ca. 2.02∼2.72 ps), the majority of the singlet CS state is short-lived, especially in polar solvents (τCR = 10.3 ps in acetonitrile, vs. 1.83 ns in toluene, 7.81 ns in n-hexane). Nanosecond transient absorption spectroscopy detects a long-lived transient species in n-hexane, which is with a mixed triplet local excited state (3 LE) and charge separated state (3 CS), the lifetime is 15.4 μs. In polar solvents, such as tetrahydrofuran and acetonitrile, a neat 3 CS state was observed, whose lifetimes are 226 ns and 142 ns, respectively. Time-resolved electron paramagnetic resonance (TREPR) spectra indicate the existence of strongly spin exchanged 3 LE/3 CT states, with the effective zero field splitting (ZFS) |D| and |E| parameters of 1484 MHz and 109 MHz, respectively, much smaller than that of the native 3 NI state (2475 and 135 MHz). It is rare but solid experimental evidence that a closely-lying 3 LE state is crucial for occurrence of TADF and this 3 LE state is an essential intermediate state to facilitate reverse intersystem crossing in TADF systems.

Long-Lived Charge-Transfer State in Spiro Compact Electron Donor-Acceptor Dyads Based on Pyromellitimide-Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization.

We observed a long‐lived charge transfer (CT) state in a novel orthogonal compact electron donor–acceptor dyads, with closed form of rhodamine (Rho) as electron donor and pyromellitimide (PI),or thionated PI, as electron acceptor. The two parts in the dyads are connected via a spiro quaternary carbon atom, thus the torsion between the donor and acceptor is completely inhibited, which is beneficial to reduce the reorganization energy and to exploit the Marcus inverted region effect to prolong the CT state lifetime. Femtosecond transient absorption spectra show that the charge separation is rather fast, while nanosecond transient absorption spectra confirmed the formation of long‐lived CT state (2.6 μs). Time‐resolved electron paramagnetic resonance (TREPR) spectra determined the spin multiplicity of the long living state and assigned it to a 3CT state. Replacement of an oxygen atom in the PI part with a sulfur atom favoring classical intersystem crossing processes, causes a consistently shortening of the lifetime of the 3CT state (0.29 μs).

Long‐Lived Charge‐Transfer State in Spiro Compact Electron Donor–Acceptor Dyads Based on Pyromellitimide‐Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization

AbstractWe observed a long‐lived charge transfer (CT) state in a novel orthogonal compact electron donor–acceptor dyads, with closed form of rhodamine (Rho) as electron donor and pyromellitimide (PI),or thionated PI, as electron acceptor. The two parts in the dyads are connected via a spiro quaternary carbon atom, thus the torsion between the donor and acceptor is completely inhibited, which is beneficial to reduce the reorganization energy and to exploit the Marcus inverted region effect to prolong the CT state lifetime. Femtosecond transient absorption spectra show that the charge separation is rather fast, while nanosecond transient absorption spectra confirmed the formation of long‐lived CT state (2.6 μs). Time‐resolved electron paramagnetic resonance (TREPR) spectra determined the spin multiplicity of the long living state and assigned it to a 3CT state. Replacement of an oxygen atom in the PI part with a sulfur atom favoring classical intersystem crossing processes, causes a consistently shortening of the lifetime of the 3CT state (0.29 μs).

Two-Photon Absorption in Electron Donor–Acceptor Dyads and Triads Using Classical and Entangled Photons: Potential Systems for Photon-to-Spin Quantum Transduction

Photon-to-spin quantum transduction, i.e., the exchange of coherence between photons and spins, is important for establishing links between localized molecular qubit systems performing logic and/or sensing operations and similar systems at different physical locations. We are developing molecular systems to explore how transduction can be implemented by using entangled photons to produce entangled spin pairs by ultrafast electron transfer leading to spin-correlated radical pairs (SCRPs). We have prepared and systematically evaluated electron transfer dyads and triads based on a 9-(N-piperidinyl)perylene-3,4-dicarboximide (6PMI) donor, a naphthalene-1,8:4,5-bis(dicarboximide) (NDI) acceptor, and a tetrathiofulvalene (TTF) secondary donor, which are prepared with and without a phenyl spacer between the 6PMI and NDI to give 6PMI-NDI, 6PMI-Ph-NDI, TTF-6PMI-NDI, and TTF-6PMI-Ph-NDI. We used transient absorption, fluorescence-detected classical two-photon-absorption, and entangled two-photon-absorption (ETPA) spectroscopies to characterize the optical properties of these systems, while time-resolved EPR spectroscopy was used to characterize their photogenerated SCRPs. The results show that the ETPA cross section depends entirely on the presence of 6PMI and NDI in the 6PMI-NDI and 6PMI-Ph-NDI dyads, but in the triads TTF-6PMI-NDI and TTF-6PMI-Ph-NDI, the presence of the Ph spacer significantly affects the ETPA cross section. These results provide important information for designing molecular systems to implement photon-to-spin quantum transduction using entangled photons.

Advanced Nonvolatile Organic Optical Memory Using Self-Assembled Monolayers of Porphyrin-Fullerene Dyads.

Photo-switchable organic field-effect transistors (OFETs) represent an important platform for designing memory devices for a diverse array of products including security (brand-protection, copy-protection, keyless entry, etc.), credit cards, tickets, and multiple wearable organic electronics applications. Herein, we present a new concept by introducing self-assembled monolayers of donor–acceptor porphyrin–fullerene dyads as light-responsive triggers modulating the electrical characteristics of OFETs and thus pave the way to the development of advanced nonvolatile optical memory. The devices demonstrated wide memory windows, high programming speeds, and long retention times. Furthermore, we show a remarkable effect of the orientation of the fullerene–polymer dyads at the dielectric/semiconductor interface on the device behavior. In particular, the dyads anchored to the dielectric by the porphyrin part induced a reversible photoelectrical switching of OFETs, which is characteristic of flash memory elements. On the contrary, the devices utilizing the dyad anchored by the fullerene moiety demonstrated irreversible switching, thus operating as read-only memory (ROM). A mechanism explaining this behavior is proposed using theoretical DFT calculations. The results suggest the possibility of revisiting hundreds of known donor–acceptor dyads designed previously for artificial photosynthesis or other purposes as versatile optical triggers in advanced OFET-based multibit memory devices for emerging electronic applications.

Synthesis and Photophysics of Phenylene Based Triplet Donor–Acceptor Dyads: ortho vs. para Positional Effect on Intramolecular Triplet Energy Transfer

Two phenylene based geometrical/isomeric triplet ortho - and para –dyads ( o – 3 and p – 3 , respectively) were synthesized and fully characterized using advanced photophysical tools and computations. In dyad o – 3 , the through-space donor-acceptor interactions led to simultaneous triplet energy transfer and charge transfer with identical kinetics. On the other hand, in the dyad p – 3 , it was found that the phenylene spacer favors a fast triplet energy delocalization over the charge transfer process. Furthermore, analysis of the results from the present investigation indicates that the deactivation of the photo-excited species ( o – 3 )* occurs through both the intrinsic channel viz. S 0 ←S 1 and charge recombination. In the case of dyad p – 3 , the results indicate that the primary deactivation pathway is self-quenching or triplet-triplet annihilation involving the acceptor unit(s).

Triplet photodynamic and up-conversion luminescence in donor–acceptor dyads with slip-stacked vs. co-facial arrangement

Engineering of donor–acceptor light-harvesting systems based on geometrical features: applications in energy transfer & energy/photon upconversion.

A long-lived charge-separated state of spiro compact electron donor-acceptor dyads based on rhodamine and naphthalenediimide chromophores.

Spiro rhodamine (Rho)-naphthalenediimide (NDI) electron donor-acceptor orthogonal dyads were prepared to generate a long-lived charge separation (CS) state based on the electron spin control approach, i.e. to form the 3CS state, not the 1CS state, to prolong the CS state lifetime by the electron spin forbidden feature of the charge recombination process of 3CS → S0. The electron donor Rho (lactam form) is attached via three σ bonds, including two C-C and one N-N bonds (Rho-NDI), or an intervening phenylene, to the electron acceptor NDI (Rho-Ph-NDI and Rho-PhMe-NDI). Transient absorption (TA) spectra show that fast intersystem crossing (ISC) (<120 fs) occurred to generate an upper triplet state localized on the NDI moiety (3NDI*), and then to form the CS state. For Rho-NDI in both non-polar and polar solvents, a long-lived 3CS state (lifetime τ = 0.13 μs) and charge separation quantum yield (Φ CS) up to 25% were observed, whereas for Rho-Ph-NDI (τ T = 1.1 μs) and Rho-PhMe-NDI (τ T = 2.0 μs), a low-lying 3NDI* state was formed by charge recombination (CR) in n-hexane (HEX). In toluene (TOL), however, CS states were observed for Rho-Ph-NDI (0.37 μs) and Rho-PhMe-NDI (0.63 μs). With electron paramagnetic resonance (EPR) spectra, weak electronic coupling between the Rho and NDI moieties for Rho-NDI was proved. Time-resolved EPR (TREPR) spectra detected two transient species including NDI-localized triplets (formed via SOC-ISC) and a 3CS state. The CS state of Rho-NDI features the largest dipolar interaction (|D| = 184 MHz) compared to Rho-Ph-NDI (|D| = 39 MHz) and Rho-PhMe-NDI (|D| = 41 MHz) due to the smallest distance between Rho and NDI moieties. For Rho-NDI, the time-dependent e,a → a,e phase change of the CS state TREPR spectrum indicates that the long-lived CS state is based on the electron spin control effect.

Long-lived charge separated state and thermally activated delayed fluorescence in anthraquinone-phenoxazine electron donor-acceptor dyads.

Long-lived charge separated (CS) triplet state (2.6 μs) and thermally activated delayed fluorescence (TADF) [τ = 282 ns (90.4%)/2.4 μs (9.6%)] were observed in an anthraquinone-phenoxazine electron donor-acceptor dyad via the electron spin control method, and emissive 1CS and non-emissive 3CS states were discriminated via nanosecond transient absorption spectroscopy and global analysis.

Origins of Large Stokes Shifts in a Pyrene–Styrene-Based Push–Pull Organic Molecular Dyad in Polar Solvents and Large Electron Mobility in the Crystalline State: A Theoretical Perspective

Push–Pull molecular chromophores are of increased research interest because of their potential as sensors in bioimaging and biomedicine as well as their promise as components in photonic and photovoltaic applications. Herein, the photophysical properties of a recently synthesized modular fluorescent probe, which was made of a pyrene- and styrene-based donor–acceptor dyad (StyPy), in different polar solvents and the charge transport in the crystalline state are investigated using first-principles density functional theory (DFT) and time-dependent DFT employing an optimally tuned range-separated hybrid functional. In agreement with the experimental observations, the calculated low-energy optical absorption of StyPy is only marginally affected by the solvent polarity. In contrast, the emission is largely red-shifted with increasing solvent polarity. Importantly, it is unveiled that the partial charge-transfer-assisted significant excited-state relaxation produces an almost planarized StyPy from the pretwisted ground-state structure, causing the observed Stokes shift. A greater frontier orbital delocalization leads to an increased spectral intensity and also to an excited-state structural rigidity as the planar StyPy suppresses the nonradiative decay, supporting an extraordinarily high fluorescence quantum yield. Furthermore, the crystalline StyPy exhibits a greater (by 2 orders of magnitude) electron mobility compared to that of holes, which is attributed to the smaller reorganization energy and larger electronic coupling for the transport of electrons than the holes. This study provides a fundamental understanding of the origins of an experimentally observed large Stokes shift for StyPy in a polar medium and also suggests crystalline StyPy as a potential n-type transport material, showing its great promise toward bioimaging and electronic applications.

Readout of spin quantum beats in a charge-separated radical pair by pump-push spectroscopy.

Spin quantum beats prove the quantum nature of reactions involving radical pairs, the key species of spin chemistry. However, such quantum beats remain hidden to transient absorption–based optical observation because the spin hardly affects the absorption properties of the radical pairs. We succeed in demonstrating such quantum beats in the photoinduced charge-separated state (CSS) of an electron donor–acceptor dyad by using two laser pulses—one for pumping the sample and another one, with variable delay, for further exciting the CSS to a higher electronic state, wherein ultrafast recombination to distinct, optically detectable products of singlet or triplet multiplicity occurs. This represents a spin quantum measurement of the spin state of the CSS at the time instant of the second (push) pulse.

Peri-N-amine-perylenes, with and without phenyl bridge: Photophysical studies and their OLED applications

Donor-bridge-acceptor framework has been studied widely for their detailed photophysical properties with the aim of efficient long range charge transfer. Carbazole attached with electron acceptors has been used for charge transfer properties, thermally activated delayed fluorescence, exciton dynamics etc. In this study, we synthesized donor–acceptor dyads of seconday amine (carbazole and diphenyl amine) attached to perylene through nitrogen, with phenyl (P-Ph-N-CBZ and P-Ph-N-BP) and without phenyl (P-N-CBZ and P-N-BP). Further their detailed photophysical and electroluminescent properties are discussed. P-N-BP is known and is used as standard in this work. DFT studies show nearly orthogonal geometry of P-N-CBZ with the dihedral angle of ∼ 71° between the planes of perylene and carbazole. For P-Ph-N-BP and P-Ph-N-CBZ, the perylene and amines are adopting almost co-planar geometries. Emission spectra of P-Ph-N-CBZ and P-N-CBZ in dichloromethane are structural with clear vibronic features while for P-Ph-N-BP and P-N-BP, the emission is structureless and broad indicating prominent electronic coupling between molecular orbitals of donor and acceptor in the latter case. Fluorescence quantum yields of phenyl-linked dyads are found to be higher than directly linked perylene-amine derivatives. High quantum yield (0.79) in non-polar hexane and polar DMSO (0.66) is observed for P-Ph-N-CBZ. It is interesting to note that the fluorescence lifetimes of these dyads are increasing while fluorescence quantum yields are decreasing with increasing polar solvents, suggesting that the emission has a significant contribution from the 1CT state. Dipole moments estimated from DFT studies and photophysical methods are higher for phenyl-linked dyads than those directly attached which is also consistent with their solvatochromism properties. Weaker electronic coupling in phenyl-linked dyads resulted due to the long distance between donor and acceptor in phenyl-linked dyads. Furthermore application in OLEDs was shown for P-Ph-N-CBZ and P-Ph-N-BP. OLEDs of P-Ph-N-BP showed a peak emission at 568 nm resulting in an amber device. A high luminance of 4.3 × 103 Cd/m2 at a current density of 100 mA/cm2 and a maximum EQE of 4.2% with a low turn on volatage of ∼ 4 V was obtained for these devices. Thus, our results show that weaker charge transfer takes place in perylene based donor–acceptor dyads resulting in bright OLED devices.

Macrocyclic Donor-Acceptor Dyads Composed of a Perylene Bisimide Dye Surrounded by Oligothiophene Bridges.

Two macrocyclic architectures comprising oligothiophene strands that connect the imide positions of a perylene bisimide (PBI) dye have been synthesized via a platinum‐mediated cross‐coupling strategy. The crystal structure of the double bridged PBI reveals all syn‐arranged thiophene units that completely enclose the planar PBI chromophore via a 12‐membered macrocycle. The target structures were characterized by steady‐state UV/Vis absorption, fluorescence and transient absorption spectroscopy, as well as cyclic and differential pulse voltammetry. Both donor–acceptor dyads show ultrafast Förster Resonance Energy Transfer and photoinduced electron transfer, thereby leading to extremely low fluorescence quantum yields even in the lowest polarity cyclohexane solvent.