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1. Accelerated Intramolecular Charge Transfer in Tetracyanobutadiene- and Expanded Tetracyanobutadiene-Incorporated Asymmetric Triphenylamine–Quinoxaline Push–Pull Conjugates

   https://doi.org/10.1021/acs.jpca.3c01732  

   Jang, Youngwoo; Sekaran, Bijesh; Singh, Prabal P; Misra, Rajneesh; D’Souza, Francis (May 2023, The Journal of Physical Chemistry A)
2. Zinc Tetrapyrrole Coordinated to Imidazole Functionalized Tetracyanobutadiene or Cyclohexa‐2,5‐diene‐1,4‐diylidene‐expanded‐tetracyanobutadiene Conjugates: Dark vs. Light‐Induced Electron Transfer

   https://doi.org/10.1002/chem.202302665  

   Guragain, Manan; Pinjari, Dilip; Misra, Rajneesh; D'Souza, Francis (October 2023, Chemistry – A European Journal)

   Abstract Using the popular metal‐ligand axial coordination self‐assembly approach, donor‐acceptor conjugates have been constructed using zinc tetrapyrroles (porphyrin (ZnP), phthalocyanine (ZnPc), and naphthalocyanine (ZnNc)) as electron donors and imidazole functionalized tetracyanobutadiene (Im‐TCBD) and cyclohexa‐2,5‐diene‐1,4‐diylidene‐expanded‐tetracyanobutadiene (Im‐DCNQ) as electron acceptors. The newly formed donor‐acceptor conjugates were fully characterized by a suite of physicochemical methods, including absorption and emission, electrochemistry, and computational methods. The measured binding constants for the 1 : 1 complexes were in the order of 10⁴–10⁵ M⁻¹in o‐dichlorobenzene. Free‐energy calculations and the energy level diagrams revealed the high exergonicity for the excited state electron transfer reactions. However, in the case of the ZnNc:Im‐DCNQ complex, owing to the facile oxidation of ZnNc and facile reduction of Im‐DCNQ, slow electron transfer was witnessed in the dark without the aid of light. Systematic transient pump‐probe studies were performed to secure evidence of excited state charge separation and gather their kinetic parameters. The rate of charge separation was as high as 10¹¹ s⁻¹suggesting efficient processes. These findings show that the present self‐assembly approach could be utilized to build donor‐acceptor constructs with powerful electron acceptors, TCBD and DCNQ, to witness ground and excited state charge transfer, fundamental events required in energy harvesting, and building optoelectronic devices. 

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3. Star-Shaped Triphenylamine–Tetracyanobutadiene–Phenothiazine Push–Pull Systems: Role of Terminal Phenothiazine in Improving Charge Transfer

   https://doi.org/10.1021/acs.jpcc.2c03495  

   Yadav, Indresh Singh; Alsaleh, Ajyal Z.; Martin, Blake; Misra, Rajneesh; D’Souza, Francis (August 2022, The Journal of Physical Chemistry C)
4. Synthesis and Understanding of the Role of Donor-Tetracyanobutadiene in Porphyrin β-Periphery toward Ultrafast Charge Transfer Dynamics

   https://doi.org/10.1021/acs.jpcc.4c05066  

   Dawson, Andrew W; Sekaran, Bijesh; Das, Somnath; Misra, Rajneesh; D’Souza, Francis (November 2024, The Journal of Physical Chemistry C)

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5. Charge stabilization via electron exchange: excited charge separation in symmetric, central triphenylamine derived, dimethylaminophenyl– tetracyanobutadiene donor–acceptor conjugates

   https://doi.org/DOI: 10.1039/D0SC04648E  

   Yadav, IS; Alsaleh, AZ; Misra, R; D'Souza, F (May 2021, Chemical science)

   Photoinduced charge separation in donor-acceptor conjugates play a pivotal role in technology breakthroughs, especially in the areas of efficient conversion of solar energy into electrical energy and fuels. Extending the lifetime of the charge separated species is a necessity for their practical utilization, and this is often achieved by following the mechanism of natural photosynthesis where the process of electron/hole migration occurs distantly separating the radical ion-pairs. Here, we hypothesize and demonstrate a new mechanism to stabilize the charge separated states via the process of electron exchange among the different acceptor entities in multimodular donor-acceptor conjugates. For this, star-shaped, central triphenylamine derived, dimethylamine-tetracyanobutadiene conjugates have been newly designed and characterized. Electron exchange was witnessed upon electroreduction in conjugates having multiple numbers of electron acceptors. Using ultrafast spectroscopy, occurrence of excited state charge separation, and the effect of electron exchange in prolonging the lifetime of charge separated states in the conjugates having multiple acceptors has been successfully demonstrated. This work constitutes the first example of stabilizing charge-separated states via the process of electron exchange. 

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