Dipyrrin based metal complexes: reactivity and catalysis

Baudron, Stéphane A.

doi:10.1039/d0dt00884b

Cited by 36 publications

(47 citation statements)

References 155 publications

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“…When compared to homoleptic compounds, heteroleptic dipyrrin complexes have provided access to a broader range of applications through the preparation of catalysts, light-emitting devices, and supramolecular structures . Inspired by the ability of the tripyrrindione scaffold to act as a hydrogen-bonding acceptor through its α-carbonyl groups, we envisioned incorporating similar interligand interactions in square planar dipyrrindione complexes to stabilize heteroleptic structures.…”

Section: Dipyrrin-19-dionementioning

confidence: 99%

Biopyrrin Pigments: From Heme Metabolites to Redox-Active Ligands and Luminescent Radicals

Tomat

Curtis

2021

Acc. Chem. Res.

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Conspectus Redox-active ligands in coordination chemistry not only modulate the reactivity of the bound metal center but also serve as electron reservoirs to store redox equivalents. Among many applications in contemporary chemistry, the scope of redox-active ligands in biology is exemplified by the porphyrin radicals in the catalytic cycles of multiple heme enzymes (e.g., cytochrome P450, catalase) and the chlorophyll radicals in photosynthetic systems. This Account reviews the discovery of two redox-active ligands inspired by oligopyrrolic fragments found in biological settings as products of heme metabolism. Linear oligopyrroles, in which pyrrole heterocycles are linked by methylene or methine bridges, are ubiquitous in nature as part of the complex, multistep biosynthesis and degradation of hemes and chlorophylls. Bile pigments, such as biliverdin and bilirubin, are common and well-studied tetrapyrroles with characteristic pyrrolin-2-one rings at both terminal positions. The coordination chemistry of these open-chain pigments is less developed than that of porphyrins and other macrocyclic oligopyrroles; nevertheless, complexes of biliverdin and its synthetic analogs have been reported, along with fluorescent zinc complexes of phytobilins employed as bioanalytical tools. Notably, linear conjugated tetrapyrroles inherit from porphyrins the ability to stabilize unpaired electrons within their π system. The isolated complexes, however, present helical structures and generally limited stability. Smaller biopyrrins, which feature three or two pyrrole rings and the characteristic oxidized termini, have been known for several decades following their initial isolation as urinary pigments and heme metabolites. Although their coordination chemistry has remained largely unexplored, these compounds are structurally similar to the well-established tripyrrin and dipyrrin ligands employed in a broad variety of metal complexes. In this context, our study of the coordination chemistry of tripyrrin-1,14-dione and dipyrrin-1,9-dione was motivated by the potential to retain on these compact, versatile platforms the reversible ligand-based redox chemistry of larger tetrapyrrolic systems. The tripyrrindione ligand coordinates several divalent transition metals (i.e., Pd(II), Ni(II) Cu(II), Zn(II)) to form neutral complexes in which an unpaired electron is delocalized over the conjugated π system. These compounds, which are stable at room temperature and exposed to air, undergo reversible one-electron processes to access different redox states of the ligand system without affecting the oxidation state and coordination geometry of the metal center. We also characterized ligand-based radicals on the dipyrrindione platform in both homoleptic and heteroleptic complexes. In addition, this study documented noncovalent interactions (e.g., interligand hydrogen bonds with the pyrrolinone carbonyls, π-stacking of ligand-centered radicals) as important aspects of this coordination chemistry. Furthermore, the fluorescence of the zinc-bound ...

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Section: Dipyrrin-19-dionementioning

confidence: 99%

Biopyrrin Pigments: From Heme Metabolites to Redox-Active Ligands and Luminescent Radicals

Tomat

Curtis

2021

Acc. Chem. Res.

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“…Pyrrole-based ligands such as dipyrromethenes (dipyrrins), − tripyrromethenes (tripyrrins), and higher analogues (oligopyrrins) have attracted attention because these ligands are capable of forming complexes with different metals such as metallodipyrrins, metallotripyrrins, and other higher analogue complexes that exhibit a variety of coordination geometries. In particular, dipyrrins have been used extensively to prepare highly fluorescent coordination complexes such as the BF 2 complex of dipyrrins (BODIPYs), which have wide applications in various research fields. − In addition, the dipyrrin ligands have been used to prepare several luminescent and nonluminescent metal complexes and their structural, physicochemical, and electronic properties have been explored. − Though several reports are available onthe coordination chemistry of dipyrrins, there have been few reports on tripyrrins and higher pyrrole-containing analogues, which may be partly due to the lack of proper synthetic strategies for preparing stable and suitable oligopyrrins.…”

Section: Introductionmentioning

confidence: 99%

Bis-Palladium Complex of α-Benzimidazole 9-Pyrrolyl Dipyrromethene: Synthesis, Structure, and Spectral and Catalytic Properties

2021

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A new ligand is designed and synthesized in two steps starting from α-formyl 3-pyrrolyl BODIPY. In the first step, the α-formyl 3-pyrrolyl BODIPY was condensed with 1,2diaminobenzene in toluene at reflux and afforded α-benzimidazole 3-pyrrolyl BODIPY in 16% yield. In the second step, αbenzimidazole 3-pyrrolyl BODIPY was decomplexed upon being treated with Lewis acid AlCl 3 and afforded the desired ligand αbenzimidazole 9-pyrrolyl dipyrromethene. However, the ligand was not very stable and reacted further with PdCl 2 in CH 3 CN for 1 h at reflux followed by recrystallization and afforded a novel bispalladium complex of α-benzimidazole 9-pyrrolyl dipyrromethene in 36% yield. The bis-palladium complex was characterized and studied by high-resolution mass spectrometry, one-and twodimensional nuclear magnetic resonance, X-ray crystallography, absorption, and density functional theory/time-dependent DFT (DFT/TD-DFT) studies. The X-ray structure revealed that two ligands and two Pd(II) ions were involved in forming a unique complex in which each Pd(II) ion was coordinated to three pyrrole N atoms of the first ligand and the benzimidazole N atom of the second ligand in a distorted square planar geometry. The absorption spectrum of the bis-palladium complex shows ill-defined, broad, and less intense bands in the region of 345−425 nm along with split bands in the higher-wavelength region of 600−630 nm. The bispalladium complex was nonfluorescent, and the results of DFT/TD-DFT studies were in agreement with the experimental observations. The preliminary studies indicated that the bis-palladium complex can act as an efficient catalyst for coupling different aryl bromides with phenylboronic acid.

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“…Numerous studies involving transition metal or main group dipyrrin bisphenols (DPP) complexes have elucidated their physicochemical properties and provided examples for possible applications of these compounds in the areas of fluorescence, [1][2][3][4][5][6][7][8][9] catalysis, [10][11][12][13][14] molecular recognition 5 and anion binding. 15 Our own laboratories have long been interested in tuning and predicting how the redox properties and oxidation states of porphyrins, 16,17 corroles 18,19 and related macrocycles can be systematically varied in nonaqueous media by the judicious addition of pre-selected complexing ligands to solution, by systematic changes in the macrocycle βor meso-substituents and/or by changing the electrochemical solvent/supporting electrolyte system.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous studies involving transition metal or main group dipyrrin-bisphenols (DPP) complexes have elucidated their physicochemical properties and provided examples for possible applications of these compounds in the areas of fluorescence, − catalysis, − molecular recognition, and anion binding …”

Section: Introductionmentioning

confidence: 99%

Solvent and Anion Effects on the Electrochemistry of Manganese Dipyrrin-Bisphenols

et al. 2020

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A series of "N2O2-type" manganese dipyrrin-bisphenols (DPP), formulated as (Ar)DPPMn, where Ar = pentafluorophenyl (F5Ph), phenyl (Ph) or mesityl (Mes), were electrochemically and spectroscopically characterized in nonaqueous media with and without added anions in the form of tetrabutylammonium salts (TBAX where X = ClO4 -, PF6 -, BF4 -, F -, Cl -, OHor CN -). Two major one-electron reductions are observed under most solution condition, the first of which is assigned as a Mn III/II process and the second as electron addition to the π-ring system as confirmed by spectroelectrochemistry. Each Mn III complex also exhibits one or two one-electron oxidations, the exact number depending upon the positive potential limit of the electrochemical solvent. The two oxidations are separated by 580-590 mV in CH3CN, 0.1 M TBAPF6 and are assigned as π-ring centered electron transfers to stepwise form a (Ar)DPPMn III π-cation radical and dication under these solution conditions. Comparisons are made between redox properties of (Ar)DPPMn and manganese(III) porphyrins, corroles and corrolazines each of which contains an innocent trianionic complexing ligand. The redox behavior and spectroscopic properties of [(Ar)DPPMn] n where n = 0, -1 or +1 are also compared to that of other structurally related [(Ar)DPPM] n complexes under similar solution conditions where M = Co II , Cu II , B III or Au III .

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Dipyrrin based metal complexes: reactivity and catalysis

Abstract: This Perspective reviews the use of dipyrrin based metal complexes as catalysts and as templates towards polypyrrolic architectures.

Cited by 36 publications

References 155 publications

Biopyrrin Pigments: From Heme Metabolites to Redox-Active Ligands and Luminescent Radicals

Biopyrrin Pigments: From Heme Metabolites to Redox-Active Ligands and Luminescent Radicals

Bis-Palladium Complex of α-Benzimidazole 9-Pyrrolyl Dipyrromethene: Synthesis, Structure, and Spectral and Catalytic Properties

Solvent and Anion Effects on the Electrochemistry of Manganese Dipyrrin-Bisphenols

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