Preparation, Structural Characterization, Assessment of Potential Antiaromaticity and Metalation of 21-Oxyazuliporphyrins

Lash, Timothy D.; Colby, Denise A.; El-Beck, Jessica A.; AbuSalim, Deyaa I.; Ferrence, Gregory M.

doi:10.1021/acs.inorgchem.5b01587

Cited by 17 publications

(38 citation statements)

References 69 publications

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“…Related organometallic complexes have also been obtained indirectly by palladium(II)-, gold(III)-, or rhodium(III)-mediated ring contractions of benziporphyrins. − In addition to the rich coordination chemistry reported for carbaporphyrinoids, selective oxidations have also been observed in reactions with transition-metal reagents. For instance, azuliporphyrins react with copper(II), silver(I), or cobalt reagents to give 21-oxyazuliporphyrins such as 9 , − while tetraphenylbenziporphyrin 10a reacts with silver(I) acetate to afford the 21-acetoxy derivative 10b . Similar reactivity is observed for dimethoxybenziporphyrins …”

Section: Introductionmentioning

confidence: 84%

Metalation and Selective Oxidation of Diphenyl-23-oxa-, -thia-, and -selena-21-carbaporphyrins

Lash

Ferrence

2017

Inorg. Chem.

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The availability of diphenyl-23-oxa-, -thia-, and -selena-21-carbaporphyrins has enabled the reactivity of these systems to be investigated and contrasted. All three heterocarbaporphyrins reacted with palladium(II) acetate in refluxing chloroform-acetonitrile to give organometallic palladium(II) derivatives in good yields. These structures are stable and give UV-vis spectra that show increasing broadening and bathochromic shifts as the size of the heteroatom increases. Nickel(II) acetate in refluxing N,N-dimethylformamide reacted with the oxa- and thiacarbaporphyrins under nitrogen to give the corresponding nickel(II) complexes, but the selenacarbaporphyrin did not metalate under these conditions. The NMR spectra for all of the metal complexes showed that they possess strong diamagnetic ring currents, although the palladium complexes gave larger downfield shifts that were slightly diminished when larger heteroatoms were present in the porphyrinoid cavity. Reactions of the oxacarbaporphyrin with nickel(II) acetate in the presence of air led to a unique oxidation reaction that afforded a weakly diatropic 21-oxycarbaporphyrin, and low yields of a related product were also obtained from the thiacarbaporphyrin.

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Section: Introductionmentioning

confidence: 84%

Metalation and Selective Oxidation of Diphenyl-23-oxa-, -thia-, and -selena-21-carbaporphyrins

Lash

Ferrence

2017

Inorg. Chem.

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“…Furthermore, azuliporphyrins undergo oxidative ring contractions to give fully aromatic benzocarbaporphyrins 2 . In addition, in the presence of air, transition metal ions such as Cu 2+ , Ag + , and Co 2+ can facilitate the formation of 21-oxyazuliporphyrins 8 . − Addition of acid to AzP generated a diprotonated species that showed substantially increased diatropic properties, and the proton NMR spectra for this type of dication showed the inner CH resonance near −2 ppm. − …”

Section: Resultsmentioning

confidence: 99%

Tropylium and Porphyrinoid Character in Carbaporphyrinoid Systems. Relative Stability and Aromatic Characteristics of Azuliporphyrin and Tropiporphyrin Tautomers, Protonated Species, and Related Structures

AbuSalim

Lash

2018

J. Phys. Chem. A

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DFT studies have been carried out on 46 azuliporphyrin (AzP) and tropiporphyrin (TrP) tautomers, cations, and dications. The structures were minimized using DFT-B3LYP/6-311++G(d,p), and the relative stabilities of the tautomers for each series were computed with M06-2X and B3LYP-D3 functionals. Nucleus independent chemical shifts, both NICS(0) and NICS(1) zz , were calculated for both the center of the macrocycles and the individual pyrrolic and carbocyclic subunits. In addition, anisotropy of induced current density (AICD) plots were generated for all of the species under investigation. The results provided insights into the favored conjugation pathways and aromatic properties of these important carbaporphyrinoid systems. The π delocalization pathways for AzP were complex, and contrary to previous speculations, there was no evidence for tropylium characteristics in the favored free base structure. The global diatropicity of AzP was found to increase with increasing solvent polarity, in agreement with experimental observations. TrP was shown to be planar and to possess a large global diamagnetic ring current. However, NICS calculations and AICD plots indicated that the cycloheptatrienyl components of the two most favored TrP tautomers have paratropic characteristics. These results are not fully consistent with the proton NMR spectra for TrPs. A dihydroTrP and a Diels−Alder adduct were investigated, and these showed exceptionally large shielding effects with NICS(1) zz values of −36.53 and −36.92 ppm, respectively, in agreement with experimental results. A silver(III) complex of tropiporphyrin was also examined, and this showed no paratropic character for the seven-membered ring, although in this case, the system was found to be severely twisted. Overall, the results provide important information about the electronic properties of AzP and TrP tautomers, as well as for related protonated species, and complement the extensive experimental studies that have been conducted on these systems.

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“…This carbaporphyrinoid system has intermediary aromatic characteristics that are enhanced upon protonation. Azuliporphyrins generate stable organometallic derivatives with Ni(II), Pd(II), Pt(II), Rh(III), Ir(III), and Ru(II) and undergo oxidative metalation with copper(II) salts . Furthermore, the seven-membered ring is prone to nucleophilic attack and this facilitates oxidative ring contractions with peroxides under basic conditions to afford benzocarbaporphyrins 2 .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Azulitriphyrins(1.2.1) and Related Benzocarbatriphyrins

2019

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Bis(pyrrolylmethyl)azulene dialdehydes underwent intramolecularMcMurry coupling, and following oxidation with DDQ and addition of trifluoroacetic acid, gave aromatic azulitriphyrin cations. The proton NMR spectra for these contracted carbaporphyrinoids showed the internal CH upfield at ca. 2 ppm, while the bridging methine units appeared downfield between 8 and 10 ppm, demonstrating that the macrocycles possess significant 14π electron diamagnetic ring currents. Although protonated azulitriphyrins(1.2.1) proved to be very stable, the free base forms were unstable and could not be isolated. Treatment of an azulitriphyrin with KOt-Bu-t-BuOOH gave rise to oxidative ring contractions that afforded the first examples of benzocarbatriphyrins. These contracted porphyrinoids also exhibit aromatic ring currents, and the internal CH resonances shifted upfield to 0.5−0.7 ppm. Protonation afforded cations with slightly enhanced diatropic properties. Nucleus independent chemical shift and anisotropy of induced current density calculations confirmed that benzocarbatriphyrins are 14π electron delocalized aromatic systems that bypass the fused arene units.

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Preparation, Structural Characterization, Assessment of Potential Antiaromaticity and Metalation of 21-Oxyazuliporphyrins

Cited by 17 publications

References 69 publications

Metalation and Selective Oxidation of Diphenyl-23-oxa-, -thia-, and -selena-21-carbaporphyrins

Metalation and Selective Oxidation of Diphenyl-23-oxa-, -thia-, and -selena-21-carbaporphyrins

Tropylium and Porphyrinoid Character in Carbaporphyrinoid Systems. Relative Stability and Aromatic Characteristics of Azuliporphyrin and Tropiporphyrin Tautomers, Protonated Species, and Related Structures

Synthesis of Azulitriphyrins(1.2.1) and Related Benzocarbatriphyrins

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