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Open accessJournal ArticleDOI: 10.1021/JACS.0C12188

Multi-stimuli Control over Assembly and Guest Binding in Metallo-supramolecular Hosts Based on Dithienylethene Photoswitches.

05 Mar 2021-Journal of the American Chemical Society (American Chemical Society (ACS))-Vol. 143, Iss: 10, pp 3865-3873
Abstract: It is difficult to assemble multi-component metallo-supramolecular architectures in a non-statistical fashion, which limits their development toward functional materials. Herein, we report a system of interconverting bowls and cages that are able to respond to various selective stimuli (light, ligands, anions), based on the self-assembly of a photochromic dithienylethene (DTE) ligand, La, with PdII cations. By combining the concept of "coordination sphere engineering", relying on bulky quinoline donors, with reversible photoswitching between the ligand's open (o-La) and closed (c-La) forms, a [Pd2(o-La)4] cage (o-C) and a [Pd2(c-La)3] bowl (c-B) were obtained, respectively. This structural rearrangement modulates the system's guest uptake capabilities. Among three bis-sulfonate guests (G1, G2, and G3), the cage can encapsulate only the smallest (G1), while the bowl binds all of them. Bowl c-B was further used to synthesize a series of heteroleptic cages, [Pd2LA3LB], representing a motif never reported before. Additional ligands (Lc-f), with short or long arms, tune the cavity size, thus enabling or preventing guest uptake. Addition of Br-/Ag+ makes it possible to change the overall charge, again triggering guest uptake and release, as well as fourth ligand de-/recomplexation. In combination, site-selective introduction of functionality and application of external stimuli lead to an intricate system of hosts with different guest preferences. A high degree of complexity is achieved through cooperativity between only a few components.

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Open accessJournal ArticleDOI: 10.1039/D1SC01226F
02 Jun 2021-Chemical Science
Abstract: Progress in metallo-supramolecular chemistry creates potential to synthesize functional nano systems and intelligent materials of increasing complexity. In the past four decades, metal-mediated self-assembly has produced a wide range of structural motifs such as helicates, grids, links, knots, spheres and cages, with particularly the latter ones catching growing attention, owing to their nano-scale cavities. Assemblies serving as hosts allow application as selective receptors, confined reaction environments and more. Recently, the field has made big steps forward by implementing dedicated functionality, e.g. catalytic centres or photoswitches to allow stimuli control. Besides incorporation in homoleptic systems, composed of one type of ligand, desire arose to include more than one function within the same assembly. Inspiration comes from natural enzymes that congregate, for example, a substrate recognition site, an allosteric regulator element and a reaction centre. Combining several functionalities without creating statistical mixtures, however, requires a toolbox of sophisticated assembly strategies. This review showcases the implementation of function into self-assembled cages and devises strategies to selectively form heteroleptic structures. We discuss first examples resulting from a combination of both principles, namely multicomponent multifunctional host-guest complexes, and their potential in application in areas such as sensing, catalysis, and photo-redox systems.

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11 Citations


Journal ArticleDOI: 10.1002/CHEM.202101057
Abstract: Spherical assemblies of the type [Pdn L2n ]2n+ can be obtained from PdII salts and curved N-donor ligands, L. It is well established that the bent angle, α, of the ligand is a decisive factor in the self-assembly process, with larger angles leading to complexes with a higher nuclearity, n. Herein, we report heteroleptic coordination cages of the type [Pdn Ln L'n ]2n+ , for which a similar correlation between the ligand bent angle and the nuclearity is observed. Tetranuclear cages were obtained by combining [Pd(CH3 CN)4 ](BF4 )2 with 1,3-di(pyridin-3-yl)benzene and ligands featuring a bent angle of α=120°. The use of a dipyridyl ligand with α=149° led to the formation of a hexanuclear complex with a trigonal prismatic geometry; for linear ligands, octanuclear assemblies of the type [Pd8 L8 L'8 ]16+ were obtained. The predictable formation of heteroleptic PdII cages from 1,3-di(pyridin-3-yl)benzene and different dipyridyl ligands is evidence that there are entire classes of heteroleptic cage structures that are privileged from a thermodynamic point of view.

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3 Citations


Journal ArticleDOI: 10.1039/D1QO00538C
Abstract: 3,3'-Bipyridine ligand B was reacted with pre-assembled [Cu-2(mu(2)-dppm)(2)] Cu(I) bimetallic flexible precursor A according to coordination-driven supramolecular chemistry synthetic principles. Outcomes obtained revealed the necessity to formally introduce bridging halide X ions (X = Cl, Br or I) in order to conduct selectively and successfully coordination-driven supramolecular syntheses. Therefore, [Cu-2(mu(2)-dppm)(2)(mu(2)-X)] bimetallic connecting nodes presenting a potential coordination angle of ca. 120 degrees are generated, which lead upon reaction with connecting ligand B to the selective formation of new tetranuclear metallacycles C-X. These derivatives are luminescent in the solid-state at room temperature with high emission quantum yields and a study of the temperature dependence of their photophysical properties was conducted, suggesting a ligand B centered triplet origin for their luminescence.

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Topics: Bipyridine (58%), Ligand (53%), Supramolecular chemistry (52%)

3 Citations


Open accessJournal ArticleDOI: 10.1021/ACS.INORGCHEM.1C01297
Abstract: New photoswitchable pyridyl-azo-phenyl-decorated tripodal host ligands (Laz) that belong to the cyclotriveratrylene family have been synthesized, and their photoswitching behavior and crystal structures determined. The latter includes a remarkable 7-fold Borromean-weave entanglement of π-π stacked layers. Trigonal bipyramidal {[Pd(en)]3(Laz)2}6+ metallo-cryptophanes (en = ethylenediamine) were formed from these and a previously known pyridyl-azo-phenyl-decorated tripodal host ligand. These coordination cages dissociate at low concentrations and are less robust to photoswitching of the Laz ligands than were previously reported Ir(III)-linked metallo-cryptophanes with similar ligands, reflecting the greater lability of the Pd-N bonds. The {[Pd(en)]3(Laz)2}6+ cages all act as hosts, binding octyl sulfate anions, or N-[2-(dimethylamino)ethyl]-1,8-naphthalimide in a dimethyl sulfoxide solution.

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Topics: Cyclotriveratrylene (52%), Ligand (51%)

2 Citations


Open accessPosted ContentDOI: 10.33774/CHEMRXIV-2021-RFD1M
30 Aug 2021-ChemRxiv
Abstract: A photoswitchable ligand and palladium(II) ions form a dynamic mixture of self-assembled metallosupramolecular structures. The photoswitching ligand is an ortho-fluoroazobenzene with appended pyridyl groups. The E-isomer is combined with palladium(II) salts affords a double-walled triangle with composition [Pd3L6]6+ and a distorted tetrahedron [Pd4L8]8+(1:2 ratio at 298 K). Irradiation with 410 nm light generates a photostationary state with ~80% of the E-isomer of the ligand which results in the selective disassembly of the tetrahedron, the more thermodynamically stable structure, and the formation of the triangle, the kinetic product. The triangle is then slowly transformed back into the tetrahedron over 2 days at 333 K. The Z-isomer of the ligand does not form any well-defined structures and has a thermal half-life of 25 days at 298K. This approach shows how a thermodynamically preferred self-assembled structure can be reversibly pumped to a kinetic trap by small perturbations of the isomer distribution using non-destructive visible light.

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2 Citations


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Journal ArticleDOI: 10.1002/ANIE.200805340
27 Apr 2009-Angewandte Chemie
Abstract: The application of self-assembled hosts as "molecular flasks" has precipitated a surge of interest in the reactivity and properties of molecules within well-defined confined spaces. The facile and modular synthesis of self-assembled hosts has enabled a variety of hosts of differing sizes, shapes, and properties to be prepared. This Review briefly highlights the various molecular flasks synthesized before focusing on their use as functional molecular containers--specifically for the encapsulation of guest molecules to either engender unusual reactions or unique chemical phenomena. Such self-assembled cavities now constitute a new phase of chemistry, which cannot be achieved in the conventional solid, liquid, and gas phases.

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Topics: Laboratory flask (52%)

1,408 Citations




Journal ArticleDOI: 10.1126/SCIENCE.1188605
Qing-Fu Sun1, Junji Iwasa1, Daichi Ogawa1, Yoshitaka Ishido1  +5 moreInstitutions (3)
28 May 2010-Science
Abstract: Self-assembly is a powerful technique for the bottom-up construction of discrete, well-defined nanoscale structures. Large multicomponent systems (with more than 50 components) offer mechanistic insights into biological assembly but present daunting synthetic challenges. Here we report the self-assembly of giant M24L48 coordination spheres from 24 palladium ions (M) and 48 curved bridging ligands (L). The structure of this multicomponent system is highly sensitive to the geometry of the bent ligands. Even a slight change in the ligand bend angle critically switches the final structure observed across the entire ensemble of building blocks between M24L48 and M12L24 coordination spheres. The amplification of this small initial difference into an incommensurable difference in the resultant structures is a key mark of emergent behavior.

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598 Citations