Porphyrins. 40. Electronic spectra and four-orbital energies of free-base, zinc, copper, and palladium tetrakis(perfluorophenyl)porphyrins

Spellane, Peter; Gouterman, Martin; Antipas, Artemis; Kim, S.; Liu, Y. C.

doi:10.1021/ic50204a021

Cited by 315 publications

(273 citation statements)

References 7 publications

(11 reference statements)

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“…Finally, all of the emission got quenched completely ( Figure 4B). It is known that the ZnTPP complex exhibits emission maxima at 600 and 656 nm, depending on the substitution, whereas the CuTPP complex has no such effect on the emission maximum, but it will quench the TPP fluorescence gradually (63). Altogether the data clearly establish the presence of H 2 TPPOAS-on the gold core.…”

Section: Resultsmentioning

confidence: 54%

Functionalized Au₂₂ Clusters: Synthesis, Characterization, and Patterning

Shibu

Radha

Verma

et al. 2009

ACS Appl. Mater. Interfaces

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We synthesized fluorescent, porphyrin-anchored, Au 22 clusters in a single step, starting from well-characterized Au 25 clusters protected with glutathione (-SG) by a combined core reduction/ligand exchange protocol, at a liquid-liquid interface. The prepared cluster was characterized by UV/vis, photoluminescence, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, elemental analysis, and matrix-assisted laser desorption ionization mass spectrometry. The absence of a 672 nm intraband transition of Au 25 and the simultaneous emergence of new characteristic peaks at 520 and 635 nm indicate the formation of the Au 22 core. An increase in the binding energy of 0.4 eV in Au 4f core-level peaks confirmed the presence of a reduced core size. Quantitative XPS confirmed the Au/S ratio. The presence of a free base, tetraphenylporphyrin (H 2 TPPOAS-), on the Au 22 core was confirmed by fluorimetric titrations with Cu 2+ and Zn 2+ ions. From all of these, the composition of the cluster was determined to be Au 22 [(-SG) 15 (-SAOPPTH 2 ) 2 ], which was supported by mass spectrometry and elemental analysis. We utilized the fluorescence nature of these water-soluble clusters for the fabrication of fluorescent patterns by soft lithography. The patterns were studied using tappingmode atomic force microscopy and confocal fluorescence imaging.

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Section: Resultsmentioning

confidence: 54%

Functionalized Au₂₂ Clusters: Synthesis, Characterization, and Patterning

Shibu

Radha

Verma

et al. 2009

ACS Appl. Mater. Interfaces

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“…We can observe the effect of symmetry if we compare TMP, DMP, and MMP. Generally, the four-orbital model is used to describe the absorption spectra of porphyrins (26,35). With free-base porphyrins, the N-H protons on the pyrrole core reduce the overall symmetry of the molecule and split the Q bands into Q x and Q y components.…”

Section: Discussionmentioning

confidence: 99%

Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

Swierk¹,

Méndez-Hernández

McCool³

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

140

107

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Solar fuel generation requires the efficient capture and conversion of visible light. In both natural and artificial systems, molecular sensitizers can be tuned to capture, convert, and transfer visible light energy. We demonstrate that a series of metal-free porphyrins can drive photoelectrochemical water splitting under broadband and red light (λ > 590 nm) illumination in a dye-sensitized TiO2 solar cell. We report the synthesis, spectral, and electrochemical properties of the sensitizers. Despite slow recombination of photoinjected electrons with oxidized porphyrins, photocurrents are low because of low injection yields and slow electron self-exchange between oxidized porphyrins. The free-base porphyrins are stable under conditions of water photoelectrolysis and in some cases photovoltages in excess of 1 V are observed.

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“…5C), a symmetry-broken electronic structure was obtained in the b 1u -type orbital, which is also one of the singly occupied molecular orbitals in the T 1 state (59). This orbital modulation is explained by the configuration interaction between the 3 (b 1u, b 3g ) and the 3 (a u, b 3g ), as has been discussed in the triplet studies on the free-base porphyrins (60,61). This difference in electronic structure (between B and C in Fig.…”

Section: Discussionmentioning

confidence: 65%

“…Concerning the S 1 state in H 2 P, based on the absorption band intensities for the Q x and Q y vibronic states compared with the B band intensity (54,62), the electronic configuration is dominated by the 1 (b 1u, b 3g ) configuration resulting from the configuration interaction between the 1 (b 1u, b 3g ) and 1 (a u, b 2g ) (61,63). The larger V CS value follows because the orbital overlap is more symmetrical in 1 V D * B .…”

Section: Discussionmentioning

confidence: 99%

Primary charge-recombination in an artificial photosynthetic reaction center

Kobori

Yamauchi

Akiyama

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

101

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Photoinduced primary charge-separation and charge-recombination are characterized by a combination of time-resolved optical and EPR measurements of a fullerene-porphyrin-linked triad that undergoes fast, stepwise charge-separation processes. The electronic coupling for the energy-wasting charge recombination is evaluated from the singlet-triplet electronic energy gap in the short-lived, primary charge-separated state. The electronic coupling is found to be smaller by Ϸ40% than that for the primary charge-separation. This inhibition of the electronic interaction for the charge-recombination to excited triplet state largely results from a symmetry-broken electronic structure modulated by configuration interaction between 3 (b1u,b3g) and 3 (au, b3g) electronic states of the free-base porphyrin.electronic coupling ͉ long-range electron transfer ͉ molecular orbital symmetry T o construct nanoscale devices or molecular wires that efficiently convert photon energies to chemical potentials, extensive studies have produced photoinduced, long-distance charge separation (CS) states by using donor (D)-acceptor (A)-linked multiarray systems that mimic natural photosynthesis (1-11). In each intramolecular, sequential electron transfer (ET) step, an electron or a hole tunnels between D and A over substantial distances (Ͼ10 Å) as in the natural photosynthetic reaction centers (12). From Marcus theory (13)(14)(15)(16)(17)(18)(19)(20), the ET rate constant (k ET ) is described (in the weak coupling regime) aswhere -h is Planck's constant divided by 2 and V, the electronic coupling matrix element, represents the electronic tunneling interaction between D and A. FCWDS denotes Franck-Condon weighted density of states parameterized by the reorganization energy ( ) and the driving force (Ϫ⌬G) for the ET reaction. The FCWDS term is given by (4where k B is the Boltzmann constant and T is the temperature. Although for several long-range ET systems, V has been interpreted in terms of a superexchange coupling model (21) that bridges the redox sites (22-28), much remains to be resolved regarding the tunneling mechanism (29-34). In addition, characterizations of V will be useful for designing molecular electronic devices (35). Key to efficient photoinduced CS is prevention of the energywasting charge recombination (CR) characterized in part by V. Although V and have been investigated for various ET steps by experimentally measuring k ET s in systems such as D 2 -D 1 -A triad (7, 9, 36) and protein complexes (24,25,34), primary CR,-A has escaped elucidation, especially in the efficient stepwise CS systems because the CR kinetics is hidden by subsequent CS processes,In the photosynthetic reaction center protein of Rhodobacter sphaeroides, which contains as cofactors a special pair (P), two bacteriopheopheophytins (H A and H B ), and two quinones (Q A and Q B ), the CR kinetics of the primary CS state of P ؉• H A Ϫ• Q A cannot easily be observed, because H A Ϫ• 3 Q A forward ET (Ϸ200 ps) is much faster than the primary CR (10-20 ns, which has b...

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Porphyrins. 40. Electronic spectra and four-orbital energies of free-base, zinc, copper, and palladium tetrakis(perfluorophenyl)porphyrins

Cited by 315 publications

References 7 publications

Functionalized Au₂₂ Clusters: Synthesis, Characterization, and Patterning

Functionalized Au₂₂ Clusters: Synthesis, Characterization, and Patterning

Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

Primary charge-recombination in an artificial photosynthetic reaction center

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Porphyrins. 40. Electronic spectra and four-orbital energies of free-base, zinc, copper, and palladium tetrakis(perfluorophenyl)porphyrins

Cited by 315 publications

References 7 publications

Functionalized Au22 Clusters: Synthesis, Characterization, and Patterning

Functionalized Au22 Clusters: Synthesis, Characterization, and Patterning

Metal-free organic sensitizers for use in water-splitting dye-sensitized photoelectrochemical cells

Primary charge-recombination in an artificial photosynthetic reaction center

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Product

Resources

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Functionalized Au₂₂ Clusters: Synthesis, Characterization, and Patterning

Functionalized Au₂₂ Clusters: Synthesis, Characterization, and Patterning