Guanidinium Binding Modulates Guest Exchange within an [M<sub>4</sub>L<sub>6</sub>] Capsule

Zarra, Salvatore; Smulders, Maarten M. J.; Lefebvre, Quentin; Clegg, Jack K.; Nitschke, Jonathan R.

doi:10.1002/anie.201202665

Cited by 56 publications

(43 citation statements)

References 47 publications

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“…These NOE interactions are consistent with the phenyl rings of B(C 6 H 4 F) 4 À resting on the triangular corners of 1. No such NOE interactions are possible should the guest be internally bound.…”

supporting

confidence: 75%

“…This mode is distinct from the external binding described by Raymond and co-workers, wherein guests undergo nonspecific interactions with the exterior of the cage and are not directly bound in a cavity. [18] To further probe the binding abilities of 1-3, we treated these hosts with tetra-p-F-and tetra-p-Cl-substituted tetraphenylborate anions (B(C 6 H 4 F) 4 À and B(C 6 H 4 Cl) 4 À ), both of which were observed to bind in fast exchange on the NMR timescale to 1-3 ( Figures S31-S37, S44-50, and S75-S82). No binding was observed for pentafluoro-or bis-m-CF 3 -substituted tetraphenylborates, or for the structurally analogous tetraphenylmethane ( Figure 2).…”

mentioning

confidence: 99%

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Peripheral Templation Generates an M^II₆L₄ Guest‐Binding Capsule

Rizzuto

Ronson

et al. 2016

Angewandte Chemie

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Pseudo-octahedral M II 6 L 4 capsules result from the subcomponent self-assembly of 2-formylphenanthroline, threefold-symmetric triamines, and octahedral metal ions. Whereas neutral tetrahedral guests and most of the anions investigated were observed to bind within the central cavity, tetraphenylborate anions bound on the outside, with one phenyl ring pointing into the cavity. This binding configuration is promoted by the complementary arrangement of the phenyl rings of the intercalated guest between the phenanthroline units of the host. The peripherally bound, rapidly exchanging tetraphenylborate anions were found to template an otherwise inaccessible capsular structure in a manner usually associated with slow-exchanging, centrally bound agents. Once formed, this cage was able to bind guests in its central cavity.

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confidence: 75%

mentioning

confidence: 99%

Peripheral Templation Generates an M^II₆L₄ Guest‐Binding Capsule

Rizzuto

Ronson

et al. 2016

Angewandte Chemie

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“…Dissociation constants for the G1 adduct of 1 were determined to be 30 μM in acetonitrile and 900 μM in 1:1 acetonitrile:water, using a non-cooperative 1:1 porphyrin–imidazole binding model25. These findings agreed with the qualitative results of the NMR experiments.…”

Section: Resultssupporting

confidence: 72%

Sequence-selective encapsulation and protection of long peptides by a self-assembled FeII8L6 cubic cage

Mosquera

Szyszko

et al. 2017

Nat Commun

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Self-assembly offers a general strategy for the preparation of large, hollow high-symmetry structures. Although biological capsules, such as virus capsids, are capable of selectively recognizing complex cargoes, synthetic encapsulants have lacked the capability to specifically bind large and complex biomolecules. Here we describe a cubic host obtained from the self-assembly of FeII and a zinc-porphyrin-containing ligand. This cubic cage is flexible and compatible with aqueous media. Its selectivity of encapsulation is driven by the coordination of guest functional groups to the zinc porphyrins. This new host thus specifically encapsulates guests incorporating imidazole and thiazole moieties, including drugs and peptides. Once encapsulated, the reactivity of a peptide is dramatically altered: encapsulated peptides are protected from trypsin hydrolysis, whereas physicochemically similar peptides that do not bind are cleaved.

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“…[1][2][3][4] In this regard, understanding the exchange mechanisms that are operative in metallo-cages allows their tuning to improve specific functions.T he features shown by metallo-cages are of wide interest for applications in binding selectivity,controlled drug delivery and modulation of reactivity of bound species,among others. [5][6][7][8][9][10][11] Thethermodynamic and kinetic stability of metal coordination cages depends on both the ligands (L) and the metal ions used in their assembly.T he properties of the included guests may also influence the stabilities of the corresponding cage complexes. [12] Pd II /Pt II -cages based on pyridyl ligands are thermodynamically and kinetically stable.The pyridyl NÀPd II bond is labile,whereas the N À Pt II counterpart is more inert at ambient conditions.…”

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confidence: 99%

Guest Exchange Mechanisms in Mono‐Metallic Pd^II/Pt^II‐Cages Based on a Tetra‐Pyridyl Calix[4]pyrrole Ligand

2019

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Planar pyridyl N-oxides are encapsulated in monometallic Pd II /Pt II -cages based on atetra-pyridyl calix[4]pyrrole ligand. The exchange dynamics of the cage complexes are slow on both the NMR chemical shift and EXSY timescales,b ut encapsulation of the guests by the cages is fast on the human timescale.A"French doors" mechanism, involving the rotation of the meso-phenyl walls of the cages,allows the passage of the planar guests.T he encapsulation of quinuclidine N-oxide, as terically more demanding guest, is slower than pyridyl Noxides in the Pd II -cage,a nd does not take place in the Pt II counterpart. Am odification of the encapsulation mechanism for the quinuclidine N-oxidei sp ostulated that requires the partial dissociation of the Pd II -cage.T he substrate binding selectivity featured by the cages is related to their different guest uptake/release mechanisms.Oneof the aims of metal-organic self-assembly is the design of molecular containers with tailored or external-stimuli controlled guest exchange dynamics. [1][2][3][4] In this regard, understanding the exchange mechanisms that are operative in metallo-cages allows their tuning to improve specific functions.T he features shown by metallo-cages are of wide interest for applications in binding selectivity,controlled drug delivery and modulation of reactivity of bound species,among others. [5][6][7][8][9][10][11] Thethermodynamic and kinetic stability of metal coordination cages depends on both the ligands (L) and the metal ions used in their assembly.T he properties of the included guests may also influence the stabilities of the corresponding cage complexes. [12] Pd II /Pt II -cages based on pyridyl ligands are thermodynamically and kinetically stable.The pyridyl NÀPd II bond is labile,whereas the N À Pt II counterpart is more inert at ambient conditions. [13,14] Fore xample,t he energy barrier for the dissociation of pyridyl ligands is ca. 22 kcal mol À1 in abanana-shaped [L 4 ·Pd 2 ] 4+ cage. [15] In contrast, the octahedral [L 4 ·Pt 6 ] 12+ cage does not show signs of dissociative processes at room temperature (rt). [16] Raymond and co-workers investigated the guest exchange mechanisms of at etrahedral [L 6 ·Ga 4 ] 12À cage.S mall cationic guests,s uch as NEt 4 + ,are bound reversibly to [L 6 ·Ga 4 ] 12À via as lippage mechanism (i.e., deformation of ac agesf ace) featuring exchange rate constants k = 10 À3 to 10 s À1 at rt. A sterically demanding guest, such as [CoCp* 2 ] + ,w hich likely requires partial ligand-metal dissociation, has adramatically decreased exchange rate,b ut the larger guest can still be displaced from the cagesc avity to the bulk solution. [17,18] Related exchange pathways were found by other groups using self-assembled capsules and cages. [19][20][21][22] We became interested in exploring the guest inclusion and exchange pathways of am ono-metallic Pd II -cage,[ 1·Pd] 2+ (Figure 1). [23] [1·Pd] 2+ features two converging polar binding sites,d efined by four pyrrole NHs of the calix[4]pyrrole core [24] and four inwardly-directed...

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Guanidinium Binding Modulates Guest Exchange within an [M₄L₆] Capsule

Cited by 56 publications

References 47 publications

Peripheral Templation Generates an M^II₆L₄ Guest‐Binding Capsule

Peripheral Templation Generates an M^II₆L₄ Guest‐Binding Capsule

Sequence-selective encapsulation and protection of long peptides by a self-assembled FeII8L6 cubic cage

Guest Exchange Mechanisms in Mono‐Metallic Pd^II/Pt^II‐Cages Based on a Tetra‐Pyridyl Calix[4]pyrrole Ligand

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Guanidinium Binding Modulates Guest Exchange within an [M4L6] Capsule

Cited by 56 publications

References 47 publications

Peripheral Templation Generates an MII6L4 Guest‐Binding Capsule

Peripheral Templation Generates an MII6L4 Guest‐Binding Capsule

Sequence-selective encapsulation and protection of long peptides by a self-assembled FeII8L6 cubic cage

Guest Exchange Mechanisms in Mono‐Metallic PdII/PtII‐Cages Based on a Tetra‐Pyridyl Calix[4]pyrrole Ligand

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Guanidinium Binding Modulates Guest Exchange within an [M₄L₆] Capsule

Peripheral Templation Generates an M^II₆L₄ Guest‐Binding Capsule

Peripheral Templation Generates an M^II₆L₄ Guest‐Binding Capsule

Guest Exchange Mechanisms in Mono‐Metallic Pd^II/Pt^II‐Cages Based on a Tetra‐Pyridyl Calix[4]pyrrole Ligand