Porphyrin Clips Derived from Diphenylglycoluril. Synthesis, Conformational Analysis, and Binding Properties

Elemans, Johannes A. A. W.; Claase, M.B.; Aarts, Patrick P. M.; Rowan, Alan E.; Schenning, Albertus P. H. J.; Nolte, Roeland J. M.

doi:10.1021/jo990112c

Cited by 85 publications

(68 citation statements)

References 27 publications

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“…Association equilibrium constants were determined by standard procedures (24) in which it was made sure that in the course of a titration experiment with a guest, the concentrations of the receptor and the second guest present in solution were kept constant.…”

Section: Methodsmentioning

confidence: 99%

“…To investigate how the measured cooperative binding effects as derived from the observed experimental binding constants are related to the intrinsic ones, we present a detailed study of the combined binding of viologens and pyridines to the bivalent zinc porphyrin receptor Zn1 (24,25) (Scheme 1). Pyridine ligands can activate and inhibit the binding of viologens in the cavity of Zn1 (see Fig.…”

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Squaring cooperative binding circles

Deutman

Monnereau

Moalin

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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The cooperative binding effects of viologens and pyridines to a synthetic bivalent porphyrin receptor are used as a model system to study how the magnitudes of these effects relate to the experimentally obtained values. The full thermodynamic and kinetic circles concerning both activation and inhibition of the cage of the receptor for the binding of viologens were measured and evaluated. The results strongly emphasize the apparent character of measured binding and rate constants, in which the fractional saturation of receptors with other guests is linearly expressed in these constants. The presented method can be used as a simple tool to better analyze and comprehend the experimentally observed kinetics and thermodynamics of natural and artificial cooperative systems.kinetics ͉ slippage ͉ supramolecular chemistry ͉ thermodynamics C ooperative binding plays an important role in nature, where it is used to construct well-defined assemblies and is used as a tool to transfer information at the cellular level (1). The formation of the tobacco mosaic virus (2) and the binding of oxygen to hemoglobin (3) are 2 well-known examples of cooperative processes. Cooperative binding interactions can be homotropic or heterotropic, when the combined binding to a multivalent receptor involves the same or different types of guests. In additions, these interactions can be positive or negative, when the binding of a guest promotes or obstructs the binding of a second guest (4).One of the challenges in the field of supramolecular chemistry is to design artificial systems that display cooperative binding effects, not only to better understand the mechanisms involved in the natural processes but also to prepare functional materials and catalysts that benefit from such binding interactions. Over the years, a large number of artificial receptors displaying positive (5-8) and negative (9-11) homotropic and positive (12-20) and negative (21-23) heterotropic cooperative binding phenomena have been developed. Although in many cases the origins of the cooperative effects could be identified, few studies have dealt in detail with the kinetics and thermodynamics of such complicated multicomponent receptor-guest systems. This is surprising, because unlike the complex biological systems, the artificial receptor-guest systems can be easily studied, and the fine details of cooperative behavior can be uncovered. It is generally known that measured association constants are context dependent in the sense that apparent values that depend on, e.g., the solvent system, salt concentrations, pH, and in the worst case impurities, are obtained (4). As a consequence, the observed cooperative binding effects might often deviate from the intrinsic ones.To investigate how the measured cooperative binding effects as derived from the observed experimental binding constants are related to the intrinsic ones, we present a detailed study of the combined binding of viologens and pyridines to the bivalent zinc porphyrin receptor Zn1 (24, 25) (Scheme 1). Pyridine ligan...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Squaring cooperative binding circles

Deutman

Monnereau

Moalin

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…[2][3][4][5][6][7][8][9][10][11][12] We have previously reported on the synthesis and guest binding properties of so-called 'porphyrin clips', cavity molecules based on diphenylglycoluril that are capped with a porphyrin roof (H22, H23). [13] Insertion of a manganese center in the porphyrin plane of H22 to give Mn2 turned the host molecule into a catalyst for the epoxidation of alkenes. When the outside of the host was shielded by coordinating a bulky axial ligand to the manganese center, the catalysis was forced to take place on the inside of the cavity.…”

Section: Introductionmentioning

confidence: 99%

“…Sanders has suggested [33] that the rigidity of most synthetic supramolecular catalysts is a drawback for catalysis and that more flexible systems might well improve the catalytic performance, because they allow a conformational response to the catalytic process, comparable to enzymes in Nature. In our group the more flexible porphyrin host 3, [13] which compared to H22 has larger and more flexible spacers connected to the meta-positions of the porphyrin phenyl groups and to the o-xylylene positions of the cavity side-walls, had already been synthesized. It showed a high degree of induced-fit behaviour for the binding of guest molecules, [13] but the association constants for a large number of guests were significantly lower than those observed for the binding of guests in rigid host 2, because the cavity of 3 is too wide to provide ideal stabilizing interactions to the guest molecules.…”

Section: Introductionmentioning

confidence: 99%

“…In our group the more flexible porphyrin host 3, [13] which compared to H22 has larger and more flexible spacers connected to the meta-positions of the porphyrin phenyl groups and to the o-xylylene positions of the cavity side-walls, had already been synthesized. It showed a high degree of induced-fit behaviour for the binding of guest molecules, [13] but the association constants for a large number of guests were significantly lower than those observed for the binding of guests in rigid host 2, because the cavity of 3 is too wide to provide ideal stabilizing interactions to the guest molecules. In order to obtain a catalyst that binds guests strongly to the inside of its cavity while still operating according to an induced fit-mechanism, porphyrin host 1 was designed.…”

Section: Introductionmentioning

confidence: 99%

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Strong Induced‐Fit Binding of Viologen and Pyridine Derivatives in Adjustable Porphyrin Cavities

Deutman

Smits

Gelder

et al. 2014

Chemistry A European J

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Abstract:The synthesis and binding properties of new porphyrin cage compounds consisting of a rigid diphenylglycoluril part, which is connected via flexible bis(ethyleneoxy) spacers to a (metal-) porphyrin 'roof', are reported. Binding of viologen guests and pyridine ligands in these porphyrin cages are accompanied by significant conformational reorganizations of the hosts. Despite these structural changes, association constants are still very high, revealing that not only receptors that bind guests according to a lock-and-key mechanism but also those that bind guests via an induced-fit mechanism can exhibit strong binding.

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