Cyclic Tetramer of a Metalloporphyrin Based on a Quadruple Hydrogen Bond

Ohkawa, Hiroyuki; Takayama, Akihiro; Nakajima, Satoshi; Nishide, Hiroyuki

doi:10.1021/ol060488u

Cited by 48 publications

(28 citation statements)

References 20 publications

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“…A diffusion-ordered spectroscopy (DOSY) NMR was carried out to probe this hypothesis. [35,36] We first performed DOSY NMR experiments on compounds 1 and 2 in DMSO, a strong hydrogenbonding acceptor solvent that has been shown to interfere with intermolecular hydrogen bonding, [37] and thus com-pounds should not be associated in solution. The diffusion coefficients D av for compounds 1 and 2 were obtained in a given solvent by averaging the D values of uncompromised peaks (without solvent overlap) (see the Supporting Information).…”

Section: Self-assembly Of Fc-peptides In Solutionmentioning

confidence: 99%

Hierarchical Organization of Ferrocene–Peptides

Beheshti

Martić

Kraatz

2012

Chemistry A European J

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Hierarchical self-assembly of disubstituted ferrocene (Fc)-peptide conjugates that possess Gly-Val-Phe and Gly-Val-Phe-Phe peptide substituents leads to the formation of nano- and micro-sized assemblies. Hydrogen-bonding and hydrophobic interactions provide directionality to the assembly patterns. The self-assembling behavior of these compounds was studied in solution by using (1)H NMR and circular dichroism (CD) spectroscopies. In the solid state, attenuated total reflectance (ATR) FTIR spectroscopy, single-crystal X-ray diffraction (XRD), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM) methods were used. Spontaneous self-assembly of Fc-peptides through intra- and intermolecular hydrogen-bonding interactions induces supramolecular assemblies, which further associate and give rise to fibers, large fibrous crystals, and twisted ropes. In the case of Fc[CO-Gly-Val-Phe-OMe](2) (1), molecules initially interact to form pleated sheets that undergo association into long fibers that form bundles and rectangular crystalline cuboids. Molecular offsets and defects, such as screw dislocations and solvent effects that occur during crystal growth, induce the formation of helical arrangements, ultimately leading to large twisted ropes. By contrast, the Fc-tetrapeptide conjugate Fc[CO-Gly-Val-Phe-Phe-OMe](2) (2) forms a network of nanofibers at the supramolecular level, presumably due to the additional hydrogen-bonding and hydrophobic interactions that stem from the additional Phe residues.

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Section: Self-assembly Of Fc-peptides In Solutionmentioning

confidence: 99%

Hierarchical Organization of Ferrocene–Peptides

Beheshti

Martić

Kraatz

2012

Chemistry A European J

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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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“…When two alkoxy groups were introduced, a supramolecular polymer instead of a cyclic hexamer was obtained. To the best of our knowledge, such a precise control has not been achieved in other hydrogen bonding mediated self-assembly systems22232425262728293031323334353637. Our strategy will provide a simple yet highly effective method for such a control.…”

Section: Discussionmentioning

confidence: 95%

Control Self-Assembly of Hydrazide-Based Cyclic Hexamers: In or Out

Yang

Huang

Chen

et al. 2013

Sci Rep

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By moving the alkoxy group on the spacer from position 5 to position 4 to add another protocol for the algorithm for intermolecular and intramolecular hydrogen bonding interactions, highly regioselectivity of noncovalent synthesis of the hydrazide-based cyclic hexamers was achieved: one out of thirteen possible isomeric cyclic hexamers selectively formed and thus precise control of the two hydrazide units in the cyclic hexamers (in or out) was accomplished.

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Cyclic Tetramer of a Metalloporphyrin Based on a Quadruple Hydrogen Bond

Cited by 48 publications

References 20 publications

Hierarchical Organization of Ferrocene–Peptides

Hierarchical Organization of Ferrocene–Peptides

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

Control Self-Assembly of Hydrazide-Based Cyclic Hexamers: In or Out

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