Porphyrin‐Based Switchable Molecular Turnstiles

Guenet, Aurélie; Graf, Ernest; Kyritsakas, Nathalie; Hosseini, Mir Wais

doi:10.1002/chem.201100057

Cited by 34 publications

(15 citation statements)

References 86 publications

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“…Besides their exceptional optical, photophysical and electrochemical properties extensively exploited for decades in donor-acceptor systems [1] and molecular photovoltaics, [2][3][4] porphyrins (Pors) have also proved to be extraordinary supramolecular scaffolds in the design of sophisticated 1D-, 2D-and 3D-dimensional architectures, [5][6][7][8][9] covalently or self-assembled, [10][11][12][13][14] including chiral materials [15][16][17] or sensors, [18] molecular cages, [19][20][21][22][23] turnstiles, [24] tweezers [25,26] and dendrimer cores. [9] Since the first reported example in 1969, [27] atropisomerism in porphyrins has been a concept widely exploited in these kinds of architectures (and, in particular, in tetra-meso-arylporphyrins).…”

Section: Introductionmentioning

confidence: 99%

Tautomerism and Atropisomerism in Free‐Base (meso)‐Strapped Porphyrins: Static and Dynamic Aspects

Urbani

Torres

2014

Chemistry A European J

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We report herein some outstanding examples of atropisomerism and tautomerism in five (meso-)strapped porphyrins. Porphyrins S0-S4 have been synthesised, characterised and studied in detail by spectroscopic and spectrometric techniques, and their isomeric purity verified by HPLC analysis. In particular, they exhibit perfectly well-defined NMR spectra that display distinct patterns depending on their average symmetry at room temperature: C2v , D2d , C2h , C2v , and D2h for S0-S4, respectively. NH tautomerism was evidenced by variable-low-temperature (1) H NMR experiments in [D2 ]dichloromethane performed on S0 (Δ${G{{{\ne}\hfill \atop {\rm 298K}\hfill}}}$=48±1 kJ mol(-1) ) and S1 (Δ${G{{{\ne}\hfill \atop {\rm 298K}\hfill}}}$=55±3 kJ mol(-1) ), which has led to an understanding of the average spectra observed for the five porphyrins at room temperature. On the other hand, S2 and S3 are stable atropisomers at room temperature, easily separated and characterised, as a result of restricted rotation of their strapped bridges due to their high rotational barrier energies. Upon heating to 82 °C, they slowly equilibrate to a thermodynamic ratio of 64:36 in favour of the more stable S2 isomer. This atropisomerisation process was evidenced by (1) H NMR spectroscopy and monitored by HPLC, from which high rotational energy barriers of 115.2 (Δ${G{{{\ne}\hfill \atop {\rm S2}\rightarrow {\rm S3}\hfill}}}$) and 116.9 kJ mol(-1) (Δ${G{{{\ne}\hfill \atop {\rm S2}\rightarrow {\rm S3}\hfill}}}$) were deduced.

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Section: Introductionmentioning

confidence: 99%

Tautomerism and Atropisomerism in Free‐Base (meso)‐Strapped Porphyrins: Static and Dynamic Aspects

Urbani

Torres

2014

Chemistry A European J

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“…A unique feature of meso-(tetraaryl)porphyrins is the constrained rotation of the aryl rings connected to the methine bridges of the porphyrin macrocycle. The rotational behavior of these aryl rings has been utilized in a number of ways including chiral and molecular recognition in asymmetric catalysis, [1][2][3][4][5][6] synthesis of biomimetic models, 7,8 design of molecular devices, [9][10][11][12][13][14][15][16][17] molecular photonics, [18][19][20] and long range communication. 21 Due to this wide versatility, both theoretical and experimental studies have addressed the underlying factors that influence the rotation of these aryl rings.…”

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confidence: 99%

Synthesis, characterization, and atropisomerism of iron complexes containing the tetrakis(2-chloro-6-fluorophenyl)porphyrinate ligand

et al. 2015

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Iron complexes of the meso-(tetraaryl)porphyrin, 5,10,15,20-tetrakis(2-chloro-6-fluorophenyl)porphine (H2ClFTPP) are reported. This unique ligand affords the opportunity to study atropisomerism in a porphyrin system containing similar substituents in the 2 and 6 positions of the meso-aryl rings. The atropisomerism displayed by the iron porphyrinates is observed to be a function of both the oxidation state of the metal and the nature of the axial ligand. In the case of iron(iii) porphyrinates, a single atropisomer is favored, whereas with the iron(ii) porphyrinate a statistical distribution of all possible atropisomers is observed. Variable temperature studies with the iron(ii) porphyrinate demonstrate that the distribution of atropisomers is maintained even at elevated temperatures. The results are discussed in the context of atropisomerism with other meso-(tetraaryl)porphyrins.

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“…The design of compound 1 (Scheme 1) is inspired by our previous investigation on Sn(IV)-porphyrin, [35][36][37][38] strapped porphyrin 39,40 or Pt(II) 41,42 based molecular turnstiles. In order to achieve reversible switching of the turnstile between its open and closed states using acids and bases as external effectors, the design of compound 1 was based on a combination of a Molecular Tectonic Laboratory, UMR UDS-CNRS 7140, icFRC, University of Strasbourg, Institut Le Bel, 4, rue Blaise Pascal, F-67000 Strasbourg, France.…”

Section: Design and Synthesismentioning

confidence: 99%

Organometallic turnstiles: acid and base locking and unlocking

2014

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A symmetrical organometallic Pt(II) based molecular turnstile 1, composed of a rotor bearing two benzonitrile units as coordinating sites and a stator equipped with a dianionic tridentate coordinating pole, undergoes a reversible switching process between two open and one closed states. In the absence of an effector, the turnstile is in its open state defined by the free rotation of the rotor around the stator. In the presence of Pd(II), the latter is simultaneously complexed by both the rotor and the stator (1-Pd) leading to the first closed state owing to locking of the rotational movement. The turnstile can be unlocked to its second open state 1-Pd-DMAP by addition of para-dimethylaminopyridine (DMAP) behaving as an external competitive ligand replacing the bound benzonitrile in the coordination sphere of the Pd centre. Upon addition of PdCl2(CH3CN)2, a competitive metal complex to remove DMAP, the turnstile is switched back to its closed state. The same process can also be achieved upon addition of MsOH causing the protonation of DMAP into DMAP-H(+) and its decomplexation and replacement by one of the two benzonitrile groups of the rotor. Finally, the deprotonation of DMAP-H(+) by addition of Et3N as a base regenerates the second open state of the turnstile.

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Porphyrin‐Based Switchable Molecular Turnstiles

Cited by 34 publications

References 86 publications

Tautomerism and Atropisomerism in Free‐Base (meso)‐Strapped Porphyrins: Static and Dynamic Aspects

Tautomerism and Atropisomerism in Free‐Base (meso)‐Strapped Porphyrins: Static and Dynamic Aspects

Synthesis, characterization, and atropisomerism of iron complexes containing the tetrakis(2-chloro-6-fluorophenyl)porphyrinate ligand

Organometallic turnstiles: acid and base locking and unlocking

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