Recent Developments on Understanding Charge Transfer in Molecular Electron Donor‐Acceptor Systems

Chen, Xi; Zhang, Xue; Xiao, Xiao; Wang, Zhijia; Zhao, Jianzhang

doi:10.1002/anie.202216010

Cited by 45 publications

(32 citation statements)

References 131 publications

(341 reference statements)

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“…As shown in the optimized S 1 structure (Figure S16b), the dihedral angle between the donor and acceptor groups was 84.7°, which was very close to 90°, beneficial to the formation of the CT state. Meanwhile, S 1 was a CT state and T 1 was a LE state (Figure S25), which fully met the requirement of the spin–orbit charge transfer intersystem crossing (SOCT-ISC). − For our systems, the transition of S 1 in our systems mixed a large component CT and n → π*. The large component CT reduced the energy gap between S 1 and T 1 , and participation of n → π* resulted in the significant spin–orbit coupling (SOC), which jointly contributed to effective ISC.…”

Section: Resultsmentioning

confidence: 52%

Organic All-Photonic Artificial Synapses Enabled by Anti-Stokes Photoluminescence

et al. 2023

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All-photonic synaptic devices with the merits of visible signals and high spatiotemporal resolution are promising to break the Von Neumann bottleneck. Although organic synapses outperform their inorganic counterpart for easy molecular modulation and lower energy consumption, the organic allphotonic artificial synapse has never been reported. Here, all-photonic synaptic characteristics were unprecedentedly observed in an organic semiconductor, (3,6dimethyl-9H-carbazol-9-yl)(thiophen-2-yl) methanone (S2OC), with anti-Stokes photoluminescence. Impressively, the intensity of fluorescence from the higher excited state (S 3 ) exhibited synaptic performance, which constantly increased with irradiation time through a channel composed of intersystem crossing, triplet− triplet annihilation, and energy transfer. More importantly, the relationship between the molecular structure and synaptic performance was established. Based on the synaptic photoplasticity property, noncontacted multilevel anticounterfeiting and imaging recognition were realized in all-photonic synapse arrays. This work provides a universal strategy for tuning the performances of organic synapses upon regulating the molecular structures, which paves the way for the application of organic semiconductors in artificial intelligence.

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Section: Resultsmentioning

confidence: 52%

Organic All-Photonic Artificial Synapses Enabled by Anti-Stokes Photoluminescence

et al. 2023

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“…[51] In summary, the major channel for (T 1 ) formation is the charge recombination based on a spin-orbit charge-transfer intersystem crossing (SOCT-ISC) mechanism. [52,53] A strong spectral overlap of GSB and fingerprints of (T 1 ) hampers a triplet quantum yield determination via target analyses of the transient absorption spectra. [4] Instead, the triplet quantum yield was approximated by means of singlet oxygen quantum yields (Φ Δ ) using C 60 as a reference.…”

Section: Time-resolved Absorption and Emission Spectroscopymentioning

confidence: 99%

One‐Pot Synthesis and Excited‐State Dynamics of Null Exciton‐Coupled Diketopyrrolopyrroles Oligo‐Grids

Hou

Wan

et al. 2023

Advanced Materials

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Exciton coupling in molecular aggregates plays a vital role in impacting and fine‐tuning optoelectronic materials and their efficiencies in devices. A versatile platform to decipher aggregation‐property relationships is built around multichromophoric architectures. Here, a series of cyclic diketopyrrolopyrrole (DPP) oligomers featuring nanoscale gridarene structures and rigid bifluorenyl spacers are designed and synthesized via one‐pot Friedel–Crafts reaction. DPP dimer [2]Grid and trimer [3]Grid, which are cyclic rigid nanoarchitectures of rather different sizes, are further characterized via steady‐state and time‐resolved absorption and fluorescence spectroscopies. They exhibit monomer‐like spectroscopic signatures in the steady‐state measurements, from which null exciton couplings are derived. Moreover, in an apolar solvent, high fluorescence quantum yields and excited‐state dynamics that resembled DPP monomer are gathered. In a polar solvent, the localized singlet excited state on a single DPP dissociates into the adjacent null coupling DPP with charge transfer characteristics. This pathway facilitates the evolution of the symmetry‐broken charge‐separated state (SB‐CS). Notable is the fact that the SB‐CS of [2]Grid is, on one hand, in equilibrium with the singlet excited state and promotes, on the other hand, the formation of the triplet excited state with a yield of 32% via charge recombination.

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“…Processes involving charge transfer or separation are ubiquitous in chemical, biological, and material sciences, and in particular, they play a key role in energy production through natural or artificial light-harvesting machineries (e.g., photovoltaic devices). Therefore, a large body of work − has been dedicated to the study and understanding of the microscopic factors that govern charge separation in various molecular systems, as well as to the design and making of molecular assemblies, such as organic bulk-heterojunctions, which can efficiently prompt charge separation and hence energy conversion. Despite its importance, however, a simple and convenient method for quantitatively determining the degree of charge separation in molecular systems is lacking.…”

Section: Introductionmentioning

confidence: 99%

C≡N Stretching Frequency as a Convenient Reporter of Charge Separation in Molecular Systems

et al. 2023

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Previously, several studies have shown that, for a set of structurally related nitrile compounds, there could be a linear relationship between the total charge on the nitrile group (q CN) and its stretching frequency (νCN). However, it is unclear whether the corresponding frequency and charge properties of structurally different nitrile compounds can be described by a single linear νCN–q CN relationship. Herein, we compute the q CN magnitudes of a large number of nitrile-containing molecules whose νCN values cover a spectral range of ca. 200 cm–1 and are measured under different experimental conditions. Our results reveal that νCN indeed exhibits a linear dependence on q CN, with a slope of 637 ± 30 cm–1/charge. Because the nitrile moiety is a commonly used building block in electronic donor–acceptor (D–A) molecular systems, we believe that this linear relationship will find utility in a wide range of applications where such D–A constructs are used, such as in organic photovoltaic assemblies. In addition, we apply this linear relationship to characterize the degree of charge transfer upon photoexcitation of two indole derivatives, 5-cyanoindole and 6-cyanoindole, and are able to show that in both cases, the fluorescence emission arises from a charge-transfer or La state.

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Recent Developments on Understanding Charge Transfer in Molecular Electron Donor‐Acceptor Systems

Cited by 45 publications

References 131 publications

Organic All-Photonic Artificial Synapses Enabled by Anti-Stokes Photoluminescence

Organic All-Photonic Artificial Synapses Enabled by Anti-Stokes Photoluminescence

One‐Pot Synthesis and Excited‐State Dynamics of Null Exciton‐Coupled Diketopyrrolopyrroles Oligo‐Grids

C≡N Stretching Frequency as a Convenient Reporter of Charge Separation in Molecular Systems

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