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Abstract A far‐red absorbing sensitizer, BF2‐chelated azadipyrromethane (azaBODIPY) has been employed as an electron acceptor to synthesize a series of push‐pull systems linked with different nitrogenous electron donors, viz.,N,N‐dimethylaniline (NND), triphenylamine (TPA), and phenothiazine (PTZ) via an acetylene linker. The structural integrity of the newly synthesized push‐pull systems was established by spectroscopic, electrochemical, spectroelectrochemical, and DFT computational methods. Cyclic and differential pulse voltammetry studies revealed different redox states and helped in the estimation of the energies of the charge‐separated states. Further, spectroelectrochemical studies performed in a thin‐layer optical cell revealed diagnostic peaks of azaBODIPY⋅−in the visible and near‐IR regions. Free‐energy calculations revealed the charge separation from one of the covalently linked donors to the1azaBODIPY* to yield Donor⋅+‐azaBODIPY⋅−to be energetically favorable in a polar solvent, benzonitrile, and the frontier orbitals generated on the optimized structures helped in assessing such a conclusion. Consequently, the steady‐state emission studies revealed quenching of the azaBODIPY fluorescence in all of the investigated push‐pull systems in benzonitrile and to a lesser extent in mildly polar dichlorobenzene, and nonpolar toluene. The femtosecond pump‐probe studies revealed the occurrence of excited charge transfer (CT) in nonpolar toluene while a complete charge separation (CS) for all three push‐pull systems in polar benzonitrile. The CT/CS products populated the low‐lying3azaBODIPY* prior to returning to the ground state. Global target (GloTarAn) analysis of the transient data revealed the lifetime of the final charge‐separated states (CSS) to be 195 ps for NND‐derived, 50 ps for TPA‐derived, and 85 ps for PTZ‐derived push‐pull systems in benzonitrile.
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Transient Absorption Spectra of Metal‐Free and Transition‐Metal 5,10,15,20‐Tetraferrocene Porphyrins: Influence of the Central Metal Ion, Solvent Polarity, and the Axial Ferrocene Ligand
Abstract The transient absorption spectra of the series of diamagnetic H2TFcP, ZnTFcP, PdTFcP, and FcInTFcP compounds (TFcP(2‐)=5,10,15,20‐tetraferroceneporphyrin dianion) were investigated in polar (DMF) and non‐polar (toluene) solvents using excitation at 650 nm. The formation and the deactivation of the charge‐separated (Fc+‐Porphyrin−.) state were observed in all cases. The lifetime of the charge‐separated state is nearly constant for all compounds (∼20 ps) and independent of the nature of the central ion and solvent. The formation of the triplet state in all the complexes was not observed. The third, minor long‐lived (160–480 ps) component was observed in polar DMF solvent. This component was tentatively assigned to the porphyrin species that are weakly bound to the carbonyl oxygen in DMF. DFT and TDDFT calculations on the ground state, excited state, and triplet state of the target compounds were in agreement with the experimental data.
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- Award ID(s):
- 2153081
- PAR ID:
- 10367084
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- European Journal of Inorganic Chemistry
- Volume:
- 2022
- Issue:
- 13
- ISSN:
- 1434-1948
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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