Synthesis, structure, electronic characterization, and halogenation of gold(III) phlorin complexes

Pistner, Allen J.; Martin, Maxwell I.; Yap, Glenn P. A.; Rosenthal, Joel

doi:10.1142/s1088424621500565

Cited by 13 publications

(26 citation statements)

References 57 publications

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“…The lactam ring possesses one outer NH and one inner CH, which couple each other in the 1 H, 1 H−COSY spectrum (Figure S9), furnishing two doublets with J = 1.6 Hz at 6.49 and 8.75 ppm, respectively. Besides, the unsymmetrical framework of 2 enables the four CH 2 groups to appear as four singlets at the 39 To assign the signals of CH 2 groups, the 1 H, 13 C-HMBC spectrum was recorded (Figure S12). The singlets of CH 2 at 2.93 ppm/3.27 ppm and the inner NH at 12.25 ppm couple with the same pyrrole carbons at 132.9, 129.5, and 125.2 ppm, indicating these two CH 2 come from the sulfolenopyrrole ring with NH.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Modification of the unique core will generate novel porphyrinoids, which have attracted considerable attention in terms of interesting structural diversities, outstanding photophysical properties, and remarkable redox activities over typical porphyrins. , Replacement of one of the four sp 2 -meso-carbons by an sp 3 -one furnishes a new type of tetrapyrrolic macrocycle, classified as phlorin (Figure ). − These new species feature excellent long-wavelength absorption, enriched redox activities, and outstanding affinity toward anion (e.g., F – , AcO – ). , Although the synthesis of phlorin can date back to 1960 when Woodward employed it as an intermediate in the total synthesis of chlorophyll, the breakthrough for efficiently preparing such macrocycles took place until early 2000. Thereafter, many novel phlorin derivatives such as N-confused phlorins, − core-modified phlorins, − and expanded phlorins − have been prepared with the aim to investigate the chemical transformations, unique photophysical properties, as well as chelating/sensing behaviors in-depth.…”

Section: Introductionmentioning

confidence: 99%

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Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

et al. 2022

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Sulfolenopyrrole-based normal and N-confused phlorins have been constructed to address the seldom touched phlorin functionalization and simultaneously explore the effect of the pyrrole linkage modes (αα, αβ) on the [4 + 2] cycloaddition reaction. The common sulfolenophlorin 1 contains two sulfolenopyrroles with the same reactivity upon tautomerization and undergoes stepwise [4 + 2]-cycloaddition with fullerene to furnish monoadduct 1-C60 and bisadduct 1-2C60 with a total yield up to 76%. By contrast, the presence of the confused pyrrole in 2 fixes the π-system owing to the low tendency to tautomerize and enables the two sulfolenopyrroles to exhibit in different fashions (i.e., normal NH-type and imino-type). Notably, under milder conditions (120 °C), the monofullerenoadduct 2-C60 forms rapidly and has been isolated from the [4 + 2] cycloaddition reaction of 2 and fullerene as the predominant fraction, accompanied by a trace amount of bisadduct 2-2C60. Raising the temperature to 140 °C did not improve the yield of 2-2C60. The structural analysis of 2-C60 indicates the attachment of fullerene at the iminopyrrole part. The high regioselectivity in the [4 + 2] cycloaddition of the imino-type sulfolenopyrrole unit has been rationalized thermodynamically by the DFT calculation on the relative energy of the two diene intermediates.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

et al. 2022

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“…Recent work has been aimed at the development of nonaromatic tetrapyrrole scaffolds (e.g., phlorins, − biladienes, − and isocorroles − ) that include an sp 3 -hybridized meso -carbon and support unique photophysical and multielectron redox properties. These nontraditional tetrapyrroles provide alternate platforms to consider for ORR and other small molecule activation processes and may offer distinct reactivity profiles and catalytic activities.…”

Section: Introductionmentioning

confidence: 99%

An Easily Prepared Monomeric Cobalt(II) Tetrapyrrole Complex That Efficiently Promotes the 4e^–/4H⁺ Peractivation of O₂ to Water

et al. 2022

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The selective 4e–/4H+ reduction of dioxygen to water is an important reaction that takes place at the cathode of fuel cells. Monomeric aromatic tetrapyrroles (such as porphyrins, phthalocyanines, and corroles) coordinated to Co(II) or Co(III) have been considered as oxygen reduction catalysts due to their low cost and relative ease of synthesis. However, these systems have been repeatedly shown to be selective for O2 reduction by the less desired 2e–/2H+ pathway to yield hydrogen peroxide. Herein, we report the initial synthesis and study of a Co(II) tetrapyrrole complex based on a nonaromatic isocorrole scaffold that is competent for 4e–/4H+ oxygen reduction reaction (ORR). This Co(II) 10,10-dimethyl isocorrole (Co[10-DMIC]) is obtained in just four simple steps and has excellent yield from a known dipyrromethane synthon. Evaluation of the steady state spectroscopic and redox properties of Co[10-DMIC] against those of Co porphyrin (cobalt 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin, [Co(TPFPP)]) and corrole (cobalt 5,10,15-tris(pentafluorophenyl)corrole triphenylphosphine, Co[TPFPC](PPh 3 )) homologues demonstrated that the spectroscopic and electrochemical properties of the isocorrole are distinct from those displayed by more traditional aromatic tetrapyrroles. Further, the investigation of the ORR activity of Co[10-DMIC] using a combination of electrochemical and chemical reduction studies revealed that this simple, unadorned monomeric Co(II) tetrapyrrole is ∼85% selective for the 4e–/4H+ reduction of O2 to H2O over the more kinetically facile 2e–/2H+ process that delivers H2O2. In contrast, the same ORR evaluations conducted for the Co porphyrin and corrole homologues demonstrated that these traditional aromatic systems catalyze the 2e–/2H+ conversion of O2 to H2O2 with near complete selectivity. Despite being a simple, easily prepared, monomeric tetrapyrrole platform, Co[10-DMIC] supports an ORR catalysis that has historically only been achieved using elaborate porphyrinoid-based architectures that incorporate pendant proton-transfer groups or ditopic molecular clefts or that impose cofacially oriented O2 binding sites. Accordingly, Co[10-DMIC] represents the first simple, unadorned, monomeric metalloisocorrole complex that can be easily prepared and shows a privileged performance for the 4e–/4H+ peractivation of O2 to water as compared to other simple cobalt containing tetrapyrroles.

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“…Porphyrins and related tetrapyrrole macrocycles support a rich photochemistry that make them appealing for a range of applications. 1,2 While a great deal is known about porphyrins and their photochemistry, much less is known about the photochemistry and photophysics of related non-aromatic tetrapyrrole architectures such as isocorroles, 3,4,[5][6][7]8,9 phlorins, 10,[11][12][13][14][15]16 and biladienes. 17 Each of these less traditional architectures contains an sp 3 -hybridized meso-carbon, which breaks the cyclic conjugation of the tetrapyrrole motif.…”

Section: Introductionmentioning

confidence: 99%

Elucidation of Complex Triplet Excited State Dynamics in Pd(II) Biladiene Tetrapyrroles

Martin

Repa

Hamburger

et al. 2022

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Pd(II) biladienes have been developed over the last five years as non-aromatic oligotetrapyrrole complexes that support a rich triplet photochemistry. In this work, we have undertaken the first detailed photophysical interrogation of three homologous Pd(II) biladienes bearing different combinations of methyl- and phenyl-substituents on the frameworks’ sp3-hybridized meso-carbon (i.e., the 10-position of the biladiene framework). These experiments have revealed unexpected excited-state dynamics that are dependent on the wavelength of light used to excite the biladiene. More specifically, transient absorption spectrosco-py revealed that higher-energy excitations (exc ~ 350-500 nm) led to an additional lifetime (i.e., an extra photophysical pro-cess) compared to experiments carried out following excitation into the lowest-energy excited states (exc = 550 nm). Each Pd(II) biladiene complex displayed an intersystem crossing lifetime on the order of tens of ps and a triplet lifetime of ~20 s, regardless of the excitation wavelength. However, when higher-energy light is used to excite the complexes, a new life-time on the order of hundreds of ps is observed. The origin of the ‘extra’ lifetime observed upon higher energy excitation of the Pd(II) biladiene complexes was revealed by detailed computational modeling using density functional theory (DFT) and time-dependent DFT (TDDFT). These efforts demonstrated that excitation into higher-energy metal-mixed-charge-transfer excited states with high spin-orbit coupling to higher energy metal-mixed-charge-transfer triplet states leads to the additional excitation deactivation pathway. Importantly, time-resolved spectroscopy and electronic structure calculations carried out for the analogous aromatic Pd(II) meso-tetrakis(pentafluorophenyl)porphyrin (Pd[TPFPP]) demonstrated this traditional tetrapyrrole does not display the excitation-wavelength dependent photophysics observed for the Pd(II) biladienes. These experiments confirm that the unusual photophysics we observe are unique to low-symmetry biladienes and do not apply to more well-studied porphyrinoids. The results of this work demonstrate that Pd(II) biladienes support a unique triplet photo-chemistry that may be exploited for development of new photochemical schemes and applications.

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Synthesis, structure, electronic characterization, and halogenation of gold(III) phlorin complexes

Cited by 13 publications

References 57 publications

Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

An Easily Prepared Monomeric Cobalt(II) Tetrapyrrole Complex That Efficiently Promotes the 4e^–/4H⁺ Peractivation of O₂ to Water

Elucidation of Complex Triplet Excited State Dynamics in Pd(II) Biladiene Tetrapyrroles

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Synthesis, structure, electronic characterization, and halogenation of gold(III) phlorin complexes

Cited by 13 publications

References 57 publications

Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

Loading Phlorins with Fullerenes by a [4 + 2]-Cycloaddition Reaction: Regulation of the Regioselectivity by Pyrrole Linkage Modes

An Easily Prepared Monomeric Cobalt(II) Tetrapyrrole Complex That Efficiently Promotes the 4e–/4H+ Peractivation of O2 to Water

Elucidation of Complex Triplet Excited State Dynamics in Pd(II) Biladiene Tetrapyrroles

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An Easily Prepared Monomeric Cobalt(II) Tetrapyrrole Complex That Efficiently Promotes the 4e^–/4H⁺ Peractivation of O₂ to Water