scholarly journals A general design approach toward covalent organic frameworks for highly efficient electrochemiluminescence

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ya-Jie Li ◽  
Wei-Rong Cui ◽  
Qiao-Qiao Jiang ◽  
Qiong Wu ◽  
Ru-Ping Liang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
High Speed ◽  
Intramolecular Charge Transfer ◽  
High Sensitivity ◽  
Covalent Organic Frameworks ◽  
Transport Networks ◽  
Promising Direction ◽  
Highly Efficient ◽  
Donor And Acceptor ◽  
Donor Acceptor

AbstractElectrochemiluminescence (ECL) plays a key role in analysis and sensing because of its high sensitivity and low background. Its wide applications are however limited by a lack of highly tunable ECL luminophores. Here we develop a scalable method to design ECL emitters of covalent organic frameworks (COFs) in aqueous medium by simultaneously restricting the donor and acceptor to the COFs’ tight electron configurations and constructing high-speed charge transport networks through olefin linkages. This design allows efficient intramolecular charge transfer for strong ECL, and no exogenous poisonous co-reactants are needed. Olefin-linked donor-acceptor conjugated COFs, systematically synthesized by combining non-ECL active monomers with C2v or C3v symmetry, exhibit strong ECL signals, which can be boosted by increasing the chain length and conjugation of monomers. The present concept demonstrates that the highly efficient COF-based ECL luminophores can be precisely designed, providing a promising direction toward COF-based ECL phosphors.

scholarly journals Predicting Excitation Energies of Twisted Intramolecular Charge-Transfer States with Time-Dependent Density Functional Theory: Comparison with Experimental Measurements in the Gas-Phase and Solvents Ranging from Hexanes to Acetonitrile

2020 ◽  
Author(s):  
James Shee ◽  
Martin Head-Gordon
Keyword(s):  
Charge Transfer ◽  
Gas Phase ◽  
Excited States ◽  
Linear Response ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Experimental Measurements ◽  
Excitation Energies ◽  
Donor And Acceptor ◽  
Donor Acceptor

Electronically-excited states characterized by intramolecular charge-transfer play an essential role in many biological processes and optical devices. The ability to make quantitative ab initio predictions of the relative energetics involved is a challenging yet desirable goal, especially for large molecules in solution. In this work we present a data set of 61 experimental measurements of absorption and emission processes, both in the gas phase and solvents representing a broad range of polarities, which involve intramolecular charge-transfer mediated by a non-zero, “twisted” dihedral angle between one or more donor and acceptor subunits. Among a variety of density functionals investigated within the framework of linear-response theory, the “optimally tuned” LRC-ωPBE functional, which utilizes a system-specific yet non-empirical procedure to specify the range-separation parameter, emerges as the preferred choice. For the entire set of excitation energies, involving changes in dipole moment ranging from 4 to >20 Debye, the mean signed and absolute errors are 0.02 and 0.18 eV, respectively (compared, e.g., to -0.30 and 0.30 for PBE0, 0.44 and 0.47 for LRC-ωPBEh, 0.83 and 0.83 for ωB97X-V). The performance of polarizable continuum solvation models for these charge-transfer excited states is closely examined, and clear trends emerge when measurements corresponding to the four small DMABN-like molecules and a charged species are excluded. We make the case that the large errors found only for small molecules in the gas phase and weak solvents cannot be expected to improve via the optimal tuning procedure, which enforces a condition that is exact only in the wellseparated donor-acceptor limit, and present empirical evidence implicating the outsized importance for small donor-acceptor systems of relaxation effects that cannot be accounted for by linear-response TDDFT within the adiabatic approximation. Finally, we demonstrate the utility of the optimally tuned density functional approach by targeting the charge-transfer states of a large biomimetic model system for light-harvesting structures in Photosystem II.

scholarly journals Controlling through-space and through-bond intramolecular charge transfer in bridged D-D’-A TADF Emitters

2021 ◽  
Author(s):  
Hector Gerardo Miranda-Salinas ◽  
Andrew P Monkman ◽  
Chih-Hao Chang ◽  
Hao-Che Kao ◽  
Dian Luo ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Acceptor Molecules

Donor-Donor’-Acceptor molecules where the Donor’ bridges the Donor and Acceptor have different possible interaction pathways for charge transfer. Here we study a series of Donor-Donor’-Acceptor molecules, having the same Acceptor...

scholarly journals Predicting Excitation Energies of Twisted Intramolecular Charge-Transfer States with Time-Dependent Density Functional Theory: Comparison with Experimental Measurements in the Gas-Phase and Solvents Ranging from Hexanes to Acetonitrile

2020 ◽  
Author(s):  
James Shee ◽  
Martin Head-Gordon
Keyword(s):  
Charge Transfer ◽  
Gas Phase ◽  
Excited States ◽  
Linear Response ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Experimental Measurements ◽  
Excitation Energies ◽  
Donor And Acceptor ◽  
Donor Acceptor

Electronically-excited states characterized by intramolecular charge-transfer play an essential role in many biological processes and optical devices. The ability to make quantitative ab initio predictions of the relative energetics involved is a challenging yet desirable goal, especially for large molecules in solution. In this work we present a data set of 61 experimental measurements of absorption and emission processes, both in the gas phase and solvents representing a broad range of polarities, which involve intramolecular charge-transfer mediated by a non-zero, “twisted” dihedral angle between one or more donor and acceptor subunits. Among a variety of density functionals investigated within the framework of linear-response theory, the “optimally tuned” LRC-ωPBE functional, which utilizes a system-specific yet non-empirical procedure to specify the range-separation parameter, emerges as the preferred choice. For the entire set of excitation energies, involving changes in dipole moment ranging from 4 to >20 Debye, the mean signed and absolute errors are 0.02 and 0.18 eV, respectively (compared, e.g., to -0.30 and 0.30 for PBE0, 0.44 and 0.47 for LRC-ωPBEh, 0.83 and 0.83 for ωB97X-V). The performance of polarizable continuum solvation models for these charge-transfer excited states is closely examined, and clear trends emerge when measurements corresponding to the four small DMABN-like molecules and a charged species are excluded. We make the case that the large errors found only for small molecules in the gas phase and weak solvents cannot be expected to improve via the optimal tuning procedure, which enforces a condition that is exact only in the wellseparated donor-acceptor limit, and present empirical evidence implicating the outsized importance for small donor-acceptor systems of relaxation effects that cannot be accounted for by linear-response TDDFT within the adiabatic approximation. Finally, we demonstrate the utility of the optimally tuned density functional approach by targeting the charge-transfer states of a large biomimetic model system for light-harvesting structures in Photosystem II.

Novel low-band-gap conjugated polymers using an alternating donor/acceptor repeat unit

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Phimwipha Piyakulawat ◽  
Anusit Keawprajak ◽  
Anon Chindaduang ◽  
Anke Helfer ◽  
Udom Asawapirom
Keyword(s):  
Cyclic Voltammetry ◽  
Charge Transfer ◽  
Conjugated Polymers ◽  
Lower Energy ◽  
Intramolecular Charge Transfer ◽  
Repeat Unit ◽  
Band Gaps ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Positive Step

AbstractA series of new π-conjugated donor-acceptor copolymers, based on a naphthalene-bisimide moiety as the electron-acceptor and connected to either thiophene or dialkylfluorene as the electron-donor, were synthesized. The polymers are soluble in common organic solvents. The UV-Vis spectra of the copolymers in chloroform showed two absorption maxima at higher energies (ca. 301 - 364 nm), assigned to the π-π * transition, and at a lower energy (ca. 512 - 595 nm), ascribed to the intramolecular charge transfer between donor and acceptor units. Cyclic voltammetry revealed that the polymers were susceptible to both electrochemical oxidation and reduction, and they had a LUMO and HOMO levels ranging from -4.07 to -3.80 eV and -6.13 to -5.64 eV, respectively. The energy band gaps were estimated to be 1.48 - 2.06 eV. These results represent a positive step towards making novel compounds suitable for electronic applications.

scholarly journals Tuning of Hyperpolarizability, One- and Two-Photon Absorption of D-A and D-A-A Type Intramolecular Charge Transfer Based Sensors

2019 ◽  
Author(s):  
Pralok K. Samanta ◽  
Md Mehboob Alam ◽  
Ramprasad Misra ◽  
Swapan K. Pati
Keyword(s):  
Charge Transfer ◽  
Gas Phase ◽  
Density Functional ◽  
Intramolecular Charge Transfer ◽  
Photon Absorption ◽  
First Hyperpolarizability ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Nlo Response ◽  
Donor Acceptor

Solvents play an important role in shaping the intramolecular charge transfer (ICT) properties of π-conjugated molecules, which in turn can affect their one-photon absorption (OPA) and two-photon absorption (TPA) as well as the static (hyper)polarizabilities. Here, we study the effect of solvent and donor-acceptor arrangement on linear and nonlinear optical (NLO) response properties of two novel ICT-based fluorescent sensors, one consisting of hemicyanine and dimethylaniline as electron withdrawing and donating groups (molecule 1), respectively and its boron-dipyrromethene (BODIPY, molecule 2)-fused counterpart (molecule 3). Density functional theoretical (DFT) calculations using long-range corrected CAM-B3LYP and M06-2X functionals, suitable for studying properties of ICT molecules, are employed to calculate the desired properties. The dipole moment (µ) as well as the total first hyperpolarizability (β<sub>total</sub>) of the studied molecules in the gas phase is dominantly dictated by the component in the direction of charge transfer. The ratios of vector component of first hyperpolarizability (β<sub>vec</sub>) to β<sub>total</sub> also reveal unidirectional charge transfer process. The properties of the medium significantly affect the OPA, hyperpolarizability and TPA properties of the studied molecules. Time dependent DFT (TDDFT) calculations suggest interchanging between two lowest excited states of molecule 3 from the gas phase to salvation. The direction of charge polarization and dominant transitions among molecular orbitals involved in the OPA and TPA processes are studied. The results presented are expected to be useful in tuning the NLO response of many ICT-based chromophores, especially those with BODIPY acceptors.<br>

scholarly journals Nanopore-induced host–guest charge transfer phenomena in a metal–organic framework

2018 ◽  
Vol 9 (13) ◽  
pp. 3282-3289 ◽  
Author(s):  
S. Yamamoto ◽  
J. Pirillo ◽  
Y. Hijikata ◽  
Z. Zhang ◽  
K. Awaga
Keyword(s):  
Charge Transfer ◽  
Self Assembly ◽  
Metal Organic Framework ◽  
Donor And Acceptor ◽  
Organic Electron ◽  
Donor Acceptor ◽  
Metal Organic ◽  
Bulk Scale ◽  
A Charge ◽  
Organic Framework

Using the “crystal sponge” approach, weak organic electron donor molecules were impregnated and evenly distributed in a crystal of a metal–organic framework (MOF), with the self-assembly of the donor–acceptor pairs with electron acceptor ligands. The nanopores of the MOF confined them and induced a charge transfer phenomenon, which would not occur between donor and acceptor molecules in a bulk scale.

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