Substituent effects in noncoplanar .pi. systems. ms-Porphins

Meot‐Ner, Michael; Adler, Alan D.

doi:10.1021/ja00851a014

Cited by 218 publications

(145 citation statements)

References 3 publications

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“…As it turned out, the order of magnitude, but also most of the pK a values, when addressed to the same porphyrin compounds, were similar to those reported elsewhere [5,10,18,37,57]. Moreover, the sequence of the pK a values collected in Table 3 appeared convergent with that of the b coefficient assigned to the porphyrin affinity for TFA ( Table 2).…”

Section: The Acid-base Equilibriumsupporting

confidence: 83%

“…The highest b is shown by 2 followed by 4, both of which containing O-phenyl components at the meso sites, which evidently activate the system, thus making the protonation much easier than with the substituents in 3 and, particularly, the sole phenyl groups in the case of 1. Similar observations were reported elsewhere [12,13,37]. Although the presented approach allows bypass of the acid-base equilibrium treatment discussed below, at this stage, the b coefficient reflecting the ''susceptibility to protonation'' (affinity for TFA) should be considered in terms of a proposal rather.…”

Section: Resultssupporting

confidence: 68%

“…Stability of the modified macrocycle has been related directly to the bonding stress resulting from hosting one or two electron acceptor species at the porphyrin core. In consequence, the symmetry of the initially quasiflat molecule considerably changes [34][35][36][37][38]. Due to redistribution of electronic density within the bonding system of the core, the newly created adducts may reveal unique chemical and photochemical properties, unlike typical porphyrins, first reflected in their absorption and fluorescence spectra [20].…”

Section: Introductionmentioning

confidence: 99%

“…It was found that electron-donating functional groups may considerably increase the activity of the porphyrin moiety towards protonation and, hence, its chemical stability [37]. This usually has been addressed to the acid/base relation in a porphyrin-protic acid system even in organic solvents, although such approximation is based on a concept dedicated primarily to aqueous solutions (HendersonHasselbalch equation).…”

Section: Introductionmentioning

confidence: 99%

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meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species

et al. 2015

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Susceptibility to interact with trifluoroacetic acid (TFA) of selected freebase porphyrins, including a novel lipophilic 3-n-pentadecyl(phenoxy)-ethoxyphenyl-substituted porphyrin, and photostability of their diprotonated compounds was explored in benzene and N,N-dimethylformamide (DMF). Results have been discussed in terms of the commonly applied pK a -based procedure and confronted with a simple approach derived from experimentally-determined correlations reflecting the porphyrins affinity for TFA. Density functional theory (DFT) has proved the porphyrin moiety creates stable diprotonated species involving two TFA molecules, in which the fluorine atoms effectively contribute to the overall interaction of the acid with the porphyrin macrocycle. The relevance of the mesosubstituent and ambient medium to the reactivity and photostability of diverse porphyrin derivatives was emphasized and referred to structural features of the investigated diprotonated porphyrins.

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Section: The Acid-base Equilibriumsupporting

confidence: 83%

Section: Resultssupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species

et al. 2015

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“…The ( 1 H, 13 C) NMR and UV-vis spectral data of the sandwich i-SAT complexes were similar to the related diprotonated species, [19][20][21] but the molar conductivities of two species were completely different. This indicates that the i-SAT complexes have been formed and not the diprotonated porphyrin species.…”

mentioning

confidence: 74%

Sandwich Intermediate Sitting-atop Complexation between Free Base meso-tetraarylporphyrins and Tellurium(IV) chloride

Dehghani

Bakhshayesh²,

Shaterian³

et al. 2010

Bulletin of the Korean Chemical Society

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Free base meso-tetraarylporphyrins (H2T(X)PP) react with tellurium(IV) chloride (TeCl4) in mild conditions for formation sandwich intermediate sitting-C NMR, UV-vis, FT-IR and elemental analysis were used for characterization of the products. In the proposed structure of the i-SAT complexes, four pyrroles of each porphyrin ring are tilted alternatively up and down and this appropriates suitable orientation of lone pairs of two pyrrolenine nitrogens for electron donation to a tellurium center. 1 H NMR and FT-IR results showed that in the produced complex, hydrogen atoms of porphyrin macrocycles remained on the pyrrole nitrogens.

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The influence of phenylethynyl linkers on the photo-physical properties of metal-free porphyrins

Baker

Bright

Detty

et al. 2000

J. Porphyrins Phthalocyanines

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Series of 5,10,15,20-tetraarylporphyrins 1 and 5,10,15,20-tetrakis[4-(arylethynyl)phenyl]porphyrins 2 were prepared via condensation of pyrrole with the appropriate benzaldehyde or 4-(arylethynyl)benzaldehyde derivative (3). Condensation of meso-phenyldipyrromethane with mixtures of benzaldehyde and 4-(trimethylsilyl-ethynyl)benzaldehyde gave a separable mixture of mono- (6), bis- (both cis-7 and trans-8) and tris[4-(trimethylsilylethynyl)phenyl]porphyrin (9). Following removal of the trimethylsilyl groups of 6–9, the 4-ethynylphenyl groups of 11–14 were coupled to 1-iodo-3,5-di(trifluoromethyl)benzene with Pd ( OAc )2 to give 15–18 bearing one, two (both cis- and trans-) and three 4-[bis-3,5-(trifluoromethyl)phenylethynyl]phenyl groups respectively. Coupling of 11 and 1-iodo-4-nitrobenzene with Pd ( OAc )2 gave porphyrin 19 with one 4-(4-nitrophenylethynyl)phenyl group. Porphyrin 24 with a p-quinone linked to the porphyrin core via a phenylethynyl group was prepared via similar chemistry. The absorbance spectra, emission maxima, excited-state fluorescence lifetimes, quantum yields of fluorescence, rates of fluorescence and rates of non-radiative decay were measured for each of the porphyrins. Absorbance spectra and emission maxima were nearly identical for all the porphyrins of this study, which suggests that the aryl groups and 4-(arylethynyl)phenyl groups are not strongly coupled to the porphyrin core in these metal-free compounds. Fluorescence quantum yields and rates of radiative decay were larger for porphyrins bearing 4-(arylethynyl)phenyl groups, while excited-state fluorescence lifetimes were somewhat shorter. These effects were additive for each additional 4-(arylethynyl)phenyl group.

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Substituent effects in noncoplanar .pi. systems. ms-Porphins

Cited by 218 publications

References 3 publications

meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species

meso-Aryl-substituted free-base porphyrins: formation, structure and photostability of diprotonated species

Sandwich Intermediate Sitting-atop Complexation between Free Base meso-tetraarylporphyrins and Tellurium(IV) chloride

The influence of phenylethynyl linkers on the photo-physical properties of metal-free porphyrins

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