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1. Charge Transfer and Spin Dynamics in a Zinc Porphyrin Donor Covalently Linked to One or Two Naphthalenediimide Acceptors

   https://doi.org/10.1021/acs.jpca.0c10471  

   Bancroft, Laura ; Zhang, Jinyuan ; Harvey, Samantha M. ; Krzyaniak, Matthew D. ; Zhang, Peng ; Schaller, Richard D. ; Beratan, David N. ; Young, Ryan M. ; Wasielewski, Michael R. ( January 2021 , The Journal of Physical Chemistry A)

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2. Anion-enhanced Excited State Charge Separation in a Spiro-locked N-Heterocycle-fused Push-Pull Zinc Porphyrin

   https://doi.org/DOI: 10.1039/d1sc00038a  

   Chahal, MK ; Liyanage, A ; Alsaleh, AZ ; Karr, PA ; Hill, JP ; D'Souza, F ( April 2021 , Chemical science)

   A new type of push-pull charge transfer complex, viz., a spiro-locked N-heterocycle-fused zinc porphyrin, ZnP-SQ, is shown to undergo excited state charge separation, which is enhanced by axial F- binding to the Zn center. In this push-pull design, the spiro-quinone group acts as a ‘lock’ promoting charge transfer interactions by constraining mutual coplanarity of the meso-phenol-substituted electron-rich Zn(II) porphyrin and an electron deficient N-heterocycle, as revealed by electrochemical and computational studies. Spectroelectrochemical studies have been used to identify the spectra of charge separated states, and charge separation upon photoexcitation of ZnP has been unequivocally established by using transient absorption spectroscopic techniques covering wide spatial and temperol regions. Further, global target analysis of the transient data using GloTarAn software is used to obtain the lifetimes of different photochemical events and reveal that fluoride anion complexation stabilizes the charge separated state to an appreciable extent. 

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3. One‐Photon Excitation Followed by a Three‐Step Sequential Energy–Energy–Electron Transfer Leading to a Charge‐Separated State in a Supramolecular Tetrad Featuring Benzothiazole–Boron‐Dipyrromethene–Zinc Porphyrin–C 60

   https://doi.org/10.1002/chem.202004262  

   Badgurjar, Deepak ; Seetharaman, Sairaman ; D'Souza, Francis ; Chitta, Raghu ( December 2020 , Chemistry – A European Journal)

   A panchromatic triad, consisting of benzothiazole (BTZ) and BF₂‐chelated boron‐dipyrromethene (BODIPY) moieties covalently linked to a zinc porphyrin (ZnP) core, has been synthesized and systematically characterized by using¹H NMR spectroscopy, ESI‐MS, UV‐visible, steady‐state fluorescence, electrochemical, and femtosecond transient absorption techniques. The absorption band of the triad, BTZ‐BODIPY‐ZnP, and dyads, BTZ‐BODIPY and BODIPY‐ZnP, along with the reference compounds BTZ‐OMe, BODIPY‐OMe, and ZnP‐OMe exhibited characteristic bands corresponding to individual chromophores. Electrochemical measurements on BTZ‐BODIPY‐ZnP exhibited redox behavior similar to that of the reference compounds. Upon selective excitation of BTZ (≈290 nm) in the BTZ‐BODIPY‐ZnP triad, the fluorescence of the BTZ moiety is quenched, due to photoinduced energy transfer (PEnT) from¹BTZ^*to the BODIPY moiety, followed by quenching of the BODIPY emission due to sequential PEnT from the¹BODIPY* moiety to ZnP, resulting in the appearance of the ZnP emission, indicating the occurrence of a two‐step singlet–singlet energy transfer. Further, a supramolecular tetrad, BTZ‐BODIPY‐ZnP:ImC₆₀, was formed by axially coordinating the triad with imidazole‐appended fulleropyrrolidine (ImC₆₀), and parallel steady‐state measurements displayed the diminished emission of ZnP, which clearly indicated the occurrence of photoinduced electron transfer (PET) from¹ZnP* to ImC₆₀. Finally, femtosecond transient absorption spectral studies provided evidence for the sequential occurrence of PEnT and PET events, namely,¹BTZ^*‐BODIPY‐ZnP:ImC₆₀→BTZ‐¹BODIPY^*‐ZnP:ImC₆₀→BTZ‐BODIPY‐¹ZnP^*:ImC₆₀→BTZ‐BODIPY‐ZnP^.+:ImC₆₀^.−in the supramolecular tetrad. The evaluated rate of energy transfer,k_EnT, was found to be 3–5×10¹⁰ s⁻¹, which was slightly faster than that observed in the case of BODIPY‐ZnP and BTZ‐BODIPY‐ZnP, lacking the coordinated ImC₆₀. The rate constants for charge separation and recombination,k_CSandk_CR, respectively, calculated by monitoring the rise and decay of C₆₀^.−were found to be 5.5×10¹⁰and 4.4×10⁸ s⁻¹, respectively, for the BODIPY‐ZnP:ImC₆₀triad, and 3.1×10¹⁰and 4.9×10⁸ s⁻¹, respectively, for the BTZ‐BODIPY‐ZnP:ImC₆₀tetrad. Initial excitation of the tetrad, promoting two‐step energy transfer and a final electron‐transfer event, has been successfully demonstrated in the present study.

    

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4. Competitive Energy and Electron Transfer in β-Functionalized Free-Base Porphyrin-Zinc Porphyrin Dimer Axially Coordinated to C 60 : Synthesis, Supramolecular Formation and Excited-State Processes

   https://doi.org/10.1002/chem.201702178  

   Hu, Yi ; Thomas, Michael B. ; Jinadasa, R. G. ; Wang, Hong ; D'Souza, Francis ( September 2017 , Chemistry - A European Journal)
5. Synthesis of Porphyrin and Bacteriochlorin Glycoconjugates through CuAAC Reaction Tuning: Synthesis of Porphyrin and Bacteriochlorin Glycoconjugates through CuAAC Reaction Tuning

   https://doi.org/10.1002/ejoc.201901128  

   Bennion, Matthew C. ; Burch, Morgan A. ; Dennis, David G. ; Lech, Melissa E. ; Neuhaus, Kira ; Fendler, Nikole L. ; Parris, Matthew R. ; Cuadra, Jessica E. ; Dixon, Charlie F. ; Mukosera, George T. ; et al ( September 2019 , European Journal of Organic Chemistry)