Photophysical Properties of a Series of Free-Base Corroles

Ding, Tang; Alemán, Elvin A.; Modarelli, David A.; Ziegler, Christopher J.

doi:10.1021/jp052047i

Cited by 190 publications

(143 citation statements)

References 46 publications

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“…Model C2 displays a splitting of the Soret band previously discussed [15] and typical of corroles with a deviation from planarity of the macrocycle induced by crowding of substituents and reported for meso aryl groups bearing bulky ortho substituents. [12,11] The dyads C2-PI, C3-PI, and C3-PPI display spectra which are essentially the superimposed absorption spectra of the component models, Figure 1. A very slight bathochro- mic shift (2-3 nm) in the absorption maximum of the dyads with respect to the components can be noticed in C2-PI and C3-PI, but it is completely absent in C3-PPI, where the insertion of a further phenyl group electronically decouples components even more.…”

Section: Photophysical Propertiesmentioning

confidence: 99%

“…[10,11,12] Free-base corroles can be connected to other units yielding photo-and thermally stable dyads able to undergo interesting photoinduced processes, such as energy [13,14,15] or electron transfer. [15] Herein we address the formation of charge-separated states following photoinduced electron transfer in new free-base corrolebased dyads.…”

Section: Introductionmentioning

confidence: 99%

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New and Efficient Arrays for Photoinduced Charge Separation Based on Perylene Bisimide and Corroles

Flamigni

Ventura

Tasior

et al. 2007

Chemistry A European J

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The bichromophoric systems C2-PI, C3-PI, and C3-PPI consisting of corrole and perylene bisimide units and representing one of the rare cases of elaborate structures based on corrole, have been synthesized. Corroles C2 and C3 are, respectively, meso-substituted corroles with 2,6-dichlorophenyl and pentafluorophenyl substituents at the 5 and 15 positions. The three dyads were prepared by divergent strategy with the corrole-forming reaction as the last step of the sequence. C2-PI and C3-PI differ in the nature of the corroles, whereas C3-PI differs from C3-PPI in the presence of a further phenyl unit in the linker between photoactive units. The dyads display spectroscopic properties which are the superposition of the component spectra, indicating a very weak electronic coupling. Excitation of the corrole unit leads to charge separation with a rate which decreases from 2.4 x 10(10), to 5.0 x 10(9), and to 4.9 x 10(7) s(-1) for C2-PI, C3-PI, and C3-PPI, respectively, where the reaction is characterized by a delta G degrees >0. Excitation of the perylene bisimide unit is followed by competing reactions of: 1) energy transfer to the corrole unit, which subsequently deactivates to the charge-separated state and; 2) electron transfer to directly form the charge-separated state. The ratio of electron-to-energy-transfer rates is 9:1 and 1:1 for C3-PI and C3-PPI, respectively. The yield of charge separation is essentially 100 % for C2-PI and C3-PI, and approximately 50 % (excitation of peryleneimide) or 15 % (excitation of the corrole) for C3-PPI. The lifetime of the charge-separated state, observed for the first time in corrole-based structures, is 540 ps for C2-PI, 2.5 ns for C3-PI, and 24 ns for C3-PPI, respectively. This is in agreement with an inverted behavior, according to Marcus theory.

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Section: Photophysical Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New and Efficient Arrays for Photoinduced Charge Separation Based on Perylene Bisimide and Corroles

Flamigni

Ventura

Tasior

et al. 2007

Chemistry A European J

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“…Corroles represent a novel, rapidly developing class of tetrapyrroles which retain the aromatic character of the porphyrin ring but differ from porphyrins by their symmetry, cavity size and flexibility [1][2][3][4][5][6]. These features result in a unique coordination chemistry of the corroles, manifested in the predominance of fivecoordinated metal complexes, which stabilize metal ions in higher oxidation states than other tetrapyrroles [4,7,8].…”

Section: Introductionmentioning

confidence: 99%

Exploring the photoexcited triplet states of aluminum and tin corroles by time-resolved Q-band EPR

et al. 2006

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The photoexcited triplet states of three 5,10,15-tris(pentafluorophenyl)corroles (tpfc), hosting Sn(IV) and AI(III) in their core, namely, Sn(Cl)(tpfc), Al(pyr)2(tpfc ) and Al(pyr)2(tpfc-Brs), were studied by time-resolved electron paramagnetic resonance (TREPR) spectroscopy in the nematic liquid crystal E7. Only two of these metallocorroles, namely, Sn(C1)(tpfc) and Al(pyr)2(tpfc-Br8), exhibit TREPR spectra following pulsed laser excitation. This result is rationalized in terms of a very low quantum yield of triplet formation in Al(pyr)2(tpfc ). Analysis of the spin polarized Q-band (34 GHz) EPR spectra of Sn(Cl)(tpfc) and Al(pyr)2(tpfc-Brs) provides detailed information on the magnetic and kinetic parameters of the triplet states as well as on the molecular ordering of the complexes in the liquid crystal. With the assignment of the zero-field splitting parameter D < 0 for the Sn(C1)(tpfc) and Al(pyr)2(tpfc-Brs), one can evaluate the dominant intersystem crossing path for these metallocorroles. Analysis reveals that in Sn(C1)(tpfc) the in-plane triplet sublevels are preferentially populated, i.e., A x, A r >> A z. This can be rationalized in terms of weak electronic interactions between the Sn(IV) ion and the corrole n-system, consistent with the domed structure of Sn(Cl)(tpfc). In Al(pyr)2(tpfc-Brs), however, the out-of-plane triplet sublevel is predominantly populated, i.e., A z > A x, Ar, which is attributed to a large increase in the spin-orbit coupling strength arising from the peripheral bromine atoms on the corrole skeleton.

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“…Therefore, great care must be taken to obtain reproducible spectra. [16,19,20] Free-base meso-triaryl corroles (e.g. phenyl, pnitrophenyl) showed a diminished and broadened Soret band when left in solution in methylene chloride and exposed to air and light during a few hours.…”

mentioning

confidence: 99%

“…phenyl, pnitrophenyl) showed a diminished and broadened Soret band when left in solution in methylene chloride and exposed to air and light during a few hours. [4,19] On the other hand, perfluorophenylcorrole is thermally more stable than regular corroles as a result of the presence of electron-withdrawing groups; nevertheless, this system decomposes after a few hours of light exposure. [4,19] Many instabilities have been observed, but until now no decomposition product has been identified and fully characterized; the only exception was an open-chain tetrapyrrole structure reported by some of us [15] and by Paolesse et al [16] We report here the first example of an autoconversion of a free-base A 2 B-corrole into its AB 2 C-porphyrin analogue at room temperature.…”

mentioning

confidence: 99%