Spectroscopic investigation of the electronic and excited state properties of para-substituted tetraphenyl porphyrins and their electrochemically generated ions.

Autor: Hanna L; Advanced Manufacturing and Energy Science, Savannah River National Laboratory, Aiken, SC 29803, USA., Movsesian E; Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St., Northridge, CA 91330, USA., Orozco M; Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St., Northridge, CA 91330, USA., Bernot AR Jr; Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St., Northridge, CA 91330, USA., Asadinamin M; Department of Physics and Astronomy, University of Georgia Athens, GA, USA., Shenje L; Department of Physics and Astronomy, University of Georgia Athens, GA, USA., Ullrich S; Department of Physics and Astronomy, University of Georgia Athens, GA, USA., Zhao Y; Department of Physics and Astronomy, University of Georgia Athens, GA, USA., Marshall N; Department of Chemistry and Physics, University of South Carolina-Aiken Aiken, SC, USA., Weeks JA; College of Natural Sciences, University of Texas Austin, Austin, TX, USA., Thomas MB; Advanced Manufacturing and Energy Science, Savannah River National Laboratory, Aiken, SC 29803, USA., Teprovich JA Jr; Department of Chemistry and Biochemistry, California State University Northridge, 18111 Nordhoff St., Northridge, CA 91330, USA. Electronic address: joseph.teprovich@csun.edu., Ward PA; Advanced Manufacturing and Energy Science, Savannah River National Laboratory, Aiken, SC 29803, USA. Electronic address: patrick.ward@srnl.doe.gov.
Jazyk: angličtina
Zdroj: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy [Spectrochim Acta A Mol Biomol Spectrosc] 2022 Oct 05; Vol. 278, pp. 121300. Date of Electronic Publication: 2022 Apr 29.
DOI: 10.1016/j.saa.2022.121300
Abstrakt: Porphyrins play pivotal roles in many crucial biological processes including photosynthesis. However, there is still a knowledge gap in understanding electronic and excited state implications associated with functionalization of the porphyrin ring system. These effects can have electrochemical and spectroscopic signatures that reveal the complex nature of these somewhat minor substitutions, beyond simple inductive or electronic effect correlations. To obtain a deeper insight into the influences of porphyrin functionalization, four free-base, meso-substituted porphyrins: tetraphenyl porphyrin (TPP), tetra(4-hydroxyphenyl) porphyrin (THPP), tetra(4-carboxyphenyl) porphyrin (TCPP), and tetra(4-nitrophenyl) porphyrin (TNPP), were synthesized, characterized, and investigated. The influence of various substituents, (-hydroxy,-carboxy, and -nitro) in the para position of the meso-substituted phenyl moieties were evaluated by spectroelectrochemical techniques (absorption and fluorescence), femtosecond transient absorption spectroscopy, cyclic and differential pulse voltammetry, ultraviolet photoelectron spectroscopy (UPS), and time-dependent density functional theory (TD-DFT). Spectral features were evaluated for the neutral porphyrins and differences observed among the various porphyrins were further explained using rendered frontier molecular orbitals pertaining to the relevant transitions. Electrochemically generated anionic and cationic porphyrin species indicate similar absorbance spectroscopic signatures attributed to a red-shift in the Soret band. Emissive behavior reveals the emergence of one new fluorescence decay pathway for the ionic porphyrin, distinct from the neutral macrocycle. Femtosecond transient absorption spectroscopy analysis provided further analysis of the implications on the excited-state as a function of the para substituent of the free-base meso-substituted tetraphenyl porphyrins. Herein, we provide an in-depth and comprehensive analysis of the electronic and excited state effects associated with systematically varying the induced dipole at the methine bridge of the free-base porphyrin macrocycle and the spectroscopic signatures related to the neutral, anionic, and cationic species of these porphyrins.
(Copyright © 2022. Published by Elsevier B.V.)
Databáze: MEDLINE
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