Helical Transition‐Metal Complexes of Constrained 2,2′‐Bidipyrrins

Bröring, Martin; Link, Stephan; Brandt, Carsten D.; Tejero, Esther Cónsul

doi:10.1002/ejic.200600986

Cited by 43 publications

(8 citation statements)

References 55 publications

(22 reference statements)

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“…[26][27][28] A substitution of hydrogen atoms for any other group at these positions would directly enhance the intramolecular repulsion and, therefore, the lability in complexes of such tetrapyrroles. 2,2'-Bidipyrrin compounds have been explored before as nitrogen-containing ligands in a number of mono-and dinuclear transition-metal chelates, [17,20,22,24,25,29,30] and the propensity of the terminal positions for chemical transformations has occasionally been documented. [31][32][33][34] Stable iron chelates, such as 2, can indeed be obtained from these ligands (Scheme 1), and we report herein the preparation, structure, spectroscopic analysis, and biomimetic reactivity of a unique series of iron 2,2'-bidipyrrin complexes [FeX-A C H T U N G T R E N N U N G (bdp)] (X = F, Cl, Br, I).…”

Section: -A C H T U N G T R E N N U N G (Bdp)]mentioning

confidence: 99%

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Iron Chelates of 2,2′‐Bidipyrrin: Stable Analogues of the Labile Iron Bilins

Bröring

Köhler

Link

et al. 2008

Chemistry A European J

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A unique series of halogenidoiron(III) complexes of the open-chain tetrapyrrolic ligand 2,2'-bidipyrrin (bpd) ([FeX(bdp)] X=F, Cl, Br, I) was prepared from simple pyrrolic and bipyrrolic precursors and iron chloride by a one-pot condensation/metalation strategy, followed by salt metathesis with CsF, LiBr, or NaI. Crystallographic analysis revealed that in all cases the 2,2'-bidipyrrin ligand is forced to reside in a helical conformation when bound to the iron atom. Whereas the extremely sensitive fluorido derivative was isolated as a CsF adduct and forms 1D polymeric chains in the solid state, the more stable chlorido, bromido, and iodido derivatives crystallize as discrete monomeric molecules with a distorted pentacoordinate iron(III) ion in an intermediate spin ground state. Magnetic susceptibility measurements and Mössbauer data of the compounds are in agreement with this interpretation. In solution, however, all the compounds are pentacoordinate with the iron atom in the high-spin (S=5/2) state and dynamic with respect to helix inversion. In the presence of air, the iron chelates react stepwise with the nucleophiles methanol and imidazolate at the tetrapyrrole terminal alpha,omega-positions, presumably through the hexacoordinate species [Fe(bdp)(MeOH)2]+ and [Fe(im)2-(bdp)](-), respectively. The successive increase of strain at these positions results in increasingly labile intermediates that spontaneously release the iron ion from the mono- or disubstituted tetrapyrrole ligands.

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Section: -A C H T U N G T R E N N U N G (Bdp)]mentioning

confidence: 99%

“…The situation is special for iron, as similar complexes of other 3d transition metals, such as Zn, Cu, Ni, Co, or Mn, are more readily available and relatively stable (though still reactive) in solution. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Abstract:…”

Section: Introductionmentioning

confidence: 99%

Iron Chelates of 2,2′‐Bidipyrrin: Stable Analogues of the Labile Iron Bilins

Bröring

Köhler

Link

et al. 2008

Chemistry A European J

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“…Depending on the kind of oligopyrrolic ligand and the type of metal employed, metal helicates have been reported as single-helix, double-helix, and triple helix comformations. Bröring and co-workers reported the synthesis of a series of helically twisted metal complexes of constrained 2,2′-bidipyrrin ligands and showed that metal ions such as Ni(II) and Pd(II) forms a singly helix where as Zn(II) forms a double helix. However, Cu(II) ion was stabilized in both single-helix and double-helix structures.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Structure, and Properties of Helical Bis-Cu(II) Complex of Linear Hexapyrrolic Ligand

2022

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The chemistry of metal helical complexes has attracted wide interest not only because of their resemblance with DNA structure but also due to their unique photophysical and chiroptical properties. Linear hexapyrrolic ligand 1 has been designed and synthesized using 3-pyrrolyl BODIPY as a key precursor. The reactivity of the appended pyrrole group of 3pyrrolyl BODIPY was taken as an advantage to synthesize bis(3pyrrolyl BODIPY) by treating 3-pyrrolyl BODIPY with 10 equiv of acetone in CHCl 3 under acid-catalyzed conditions and afforded bis(3-pyrrolyl BODIPY) 2 in 20% yield. Bis(3-pyrrolyl BODIPY) 2, in which two 3-pyrrolyl BODIPY units were connected via sp 3 meso carbon, was very stable, and its identity was confirmed by HR-MS, NMR, and X-ray crystallographic analysis. The X-ray structure revealed that the 3-pyrrolyl BODIPY moieties in bis(3pyrrolyl BODIPY) 2 remained almost planar and arranged at an angle of 98.4°with each other, leading to a V-shaped conformation. In the next step, bis(3-pyrrolyl BODIPY) 2 was treated with AlCl 3 in acetonitrile/methanol at reflux to afford hexapyrrolic ligand 1. Hexapyrrolic ligand 1 was treated with CuCl 2 in acetonitrile at room temp for 1 h followed by crystallization to afford helical bis-Cu(II) complex 1-Cu. Bis-Cu(II) complex 1-Cu was characterized and studied by HR-MS, X-ray crystallography, ESR, absorption, and DFT/TD-DFT techniques. The X-ray structure revealed that the bis-Cu(II) complex was a double-stranded bimetallic helicate and each Cu(II) ion was coordinated to four nitrogen atoms of two dipyrrin units from two hexapyrrolic ligands in a distorted tetrahedral geometry. The crystal packing diagram showed that the bis-Cu(II) complex formed as a racemic mixture containing both M and P isomers which was unable to isolate. The ESR spectrum of bis-Cu(II) complex 1-Cu indicated the presence of two noninteracting Cu(II) ions in slightly different coordination environments. DFT and TD-DFT studies were in agreement with the experimental observations of bis(3-pyrrolyl BODIPY) 2 complex and bis-Cu(II) complex 1-Cu.

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“…As potential building subunits of helical assemblies, linear tetrapyrrole ligands, bidipyrrins, that is, directly linked dipyrrin dimers, [8,9] can be used to fabricate metal complexes, including [2 + 2]-type Zn II -assisted double helices [10] as well as roughly square-planar complexes formed with Ni II , Cu II , and Pd II[11] (Scheme 1). Because of the coordination properties of dipyrrins as monoanionic bidentate ligands, bidipyrrin-Zn II double helices are electronically neutral and therefore their enantiomers would be isolated from the racemic mixture by facile protocols such as chiral HPLC.…”

Section: Introductionmentioning

confidence: 99%

Formation of Metal‐Assisted Stable Double Helices in Dimers of Cyclic Bis‐Tetrapyrroles that Exhibit Spring‐Like Motion

Hashimoto

Nishimura

Lim

et al. 2010

Chemistry A European J

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Bidipyrrin-bridged macrocycles, prepared from Ni(II)-bridged dipyrrin-based nanorings by intramolecular oxidative biaryl coupling reactions, yielded [2+4]-type Zn(II)-assisted stable twisted-ring dimers comprising two double helices. These [2+4]-type metal complexes can be optically resolved by chiral HPLC and exhibit tunable electronic and optical properties as a result of spring-like motions. The double helices behave as glue to connect two macrocycles and as the screws of hinges to form thermally responsive synchronized spring systems.

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Helical Transition‐Metal Complexes of Constrained 2,2′‐Bidipyrrins

Cited by 43 publications

References 55 publications

Iron Chelates of 2,2′‐Bidipyrrin: Stable Analogues of the Labile Iron Bilins

Iron Chelates of 2,2′‐Bidipyrrin: Stable Analogues of the Labile Iron Bilins

Synthesis, Structure, and Properties of Helical Bis-Cu(II) Complex of Linear Hexapyrrolic Ligand

Formation of Metal‐Assisted Stable Double Helices in Dimers of Cyclic Bis‐Tetrapyrroles that Exhibit Spring‐Like Motion

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