Photoinduced Proton-Coupled Electron Transfer in Supramolecular Sn-IV Di(L-tyrosinato) Porphyrin Conjugates
| Autor: | Agnese Amati, Barbara Ventura, Sebastiano Merchiori, Mirco Natali, Elisabetta Iengo |
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| Přispěvatelé: | Natali, M., Amati, A., Merchiori, S., Ventura, B., Iengo, E. |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Photophysical investigation
Proton coupled electron transfers Photophysical characterization Supramolecular chemistry Synthesis and characterizations 02 engineering and technology 010402 general chemistry Photochemistry 01 natural sciences tin porphyrin HYDROGEN-BONDED PHENOLS CONCERTED PROTON TYROSINE OXIDATION EXCITED-STATES TRANSFER EPT TRYPTOPHAN DISTANCE TRIAD DEPENDENCE CHEMISTRY Electron transfer chemistry.chemical_compound Quenching mechanisms Proton-Coupled Electron Transfer Physical and Theoretical Chemistry Tetraphenyl porphyrins Substantial reorganization Kinetic isotope effects Ambientale 021001 nanoscience & nanotechnology Porphyrin 0104 chemical sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials General Energy chemistry Proton-coupled electron transfer 0210 nano-technology Conjugate |
| Zdroj: | Journal of physical chemistry. C 124 (2020): 8514–8525. doi:10.1021/acs.jpcc.0c00224 info:cnr-pdr/source/autori:Natali, Mirco; Amati, Agnese; Merchiori, Sebastiano; Ventura, Barbara; Iengo, Elisabetta/titolo:Photoinduced Proton-Coupled Electron Transfer in Supramolecular Sn-IV Di(L-tyrosinato) Porphyrin Conjugates/doi:10.1021%2Facs.jpcc.0c00224/rivista:Journal of physical chemistry. C/anno:2020/pagina_da:8514/pagina_a:8525/intervallo_pagine:8514–8525/volume:124 |
| DOI: | 10.1021/acs.jpcc.0c00224 |
| Popis: | Proton-coupled electron transfer (PCET) plays a key role in many biological processes, and a thorough comprehension of its subtle mechanistic complexity requires the synthesis and characterization of suitable artificial systems capable of mimicking this fundamental, elementary step. Herein, we report on a detailed photophysical investigation of conjugate 1, based on a tin(IV) tetraphenylporphyrin (SnTPP) chromophore bound to two l-tyrosinato amino acids, in CH2Cl2 in combination with organic bases of different strength and the preparation of a novel conjugate 3, based on a tin(IV) octaethylporphyrin (SnOEP) in place of the tetraphenyl analogue, and its photophysical characterization in CH2Cl2 in the presence of pyrrolidine. In the case of compound 1 with all bases examined, quenching of both the singlet and triplet excited states is observed and attributed to the occurrence of concerted proton-electron transfer (CPET). Rates and quenching yields decrease with the strength of the base used, consistent with the decrease of the driving force for the CPET process. Conjugate 3 with pyrrolidine is quenched only at the triplet level by CPET, albeit with slower rates than its parent compound 1, ascribable to the smaller driving force as a result of SnOEP being more difficult to reduce than SnTPP. For both systems, the quenching mechanism is confirmed by suitable blank experiments, specific kinetic treatments, and the observation of kinetic isotope effects (KIEs). Differently from what has been previously proposed, a detailed reinvestigation of the triplet quenching of 1 with pyrrolidine shows that no long-lived radical pair state is formed, as diradical recombination is always faster than formation. This is true for both 1 and 3 and for all bases examined. The kinetics of the CPET pathways can be well described according to Marcus theory and point toward the involvement of substantial reorganization energy as typically observed for PCET processes of concerted nature. |
| Databáze: | OpenAIRE |
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