In the self‐assembly of PdII ions and two different, but similarly shaped, ligands (1 and 2), neither random mixing nor self‐sorting of the two ligands into two unmixed structures was observed. ...Instead a mixed, yet sorted, Pd12(1)12(2)12 cantellated tetrahedron (and its pseudoisomer) was selectively formed, thus revealing a fine example of intramolecular self‐sorting. A case study showed that a homothetic ratio of >2 is necessary to observe cantellated tetrahedra.
Intramolecular self‐sorting: The complexation of PdII ions with two similarly shaped ligands with distinctly different bridging lengths has generated a Pd12(L1)12(L2)12 cantellated tetrahedron and its pseudoisomer in which the two ligands are mixed but are regularly mapped onto the polyhedral framework. A study showed that a homothetic ratio of >2 is necessary to observe cantellated tetrahedra.
Discrete organopalladium coordination cages have shown great potential in applications ranging from molecular recognition and sensing, drug delivery to enzymatic catalysis. While many of the known ...organopalladium cages are homoleptic structures with regular polyhedral shapes and symmetric inner cavities, heteroleptic cages with complex architectures and new functions coming from their anisotropic cavities have received an increasing attention recently. In this concept article, we discuss a powerful combinatorial coordination self‐assembly strategy toward the construction of a family of organopalladium cages, including both homoleptic and heteroleptic ones, from a given library of ligands. Within such a cage family, the heteroleptic cages often feature systematically fine‐tuned structures and emergent properties, distinct from their parent homoleptic counterparts. We hope the concepts and examples provided in this article can offer some rational guidance for the design of new coordination cages toward advanced functions.
Combinatorial coordination self‐assembly is a powerful tool to create the lower‐symmetric coordination cages with increasing structural complexities and advanced functions. In this concept article, we define and summarized the strategy for the combinatorial self‐assembled PdII coordination cages. Emergent functions on some selected PdII coordination cages were also introduced with an aim of emphasizing the advantages of the heteroleptic cages.
Lanthanide supramolecular chemistry is a fast growing and intriguing research field due to the unique photophysical, magnetic, and coordination properties of lanthanide ions (Ln
). Compared with the ...intensively investigated mononuclear Ln-complexes, polymetallic lanthanide supramolecular assemblies offer more structural superiority and functional advantages. In recent decades, significant progress has been made in polynuclear lanthanide supramolecules, varying from structural evolution to luminescent and magnetic functional materials. This review summarizes the design principles in ligand-induced coordination-driven self-assembly of polynuclear Ln-structures and intends to offer guidance for the construction of more elegant Ln-based architectures and optimization of their functional performances. Design principles concerning the water solubility and chirality of the lanthanide-organic assemblies that are vital in extending their applications are emphasized. The strategies for improving the luminescent properties and the applications in up-conversion, host-guest chemistry, luminescent sensing, and catalysis have been summarized. Magnetic materials based on supramolecular assembled lanthanide architectures are given in an individual section and are classified based on their structural features. Challenges remaining and perspective directions in this field are also briefly discussed.
Container-molecules are attractive to chemists due to their unique structural characteristics comparable to enzymes and receptors in nature. We report here a family of artificial self-assembled ...macrocyclic containers that feature induced-fit transformations in response to different anionic guests. Five metal-organic macrocycles with empirical formula of M
L
(M=Metal; L=Ligand; n=3, 4, 5, 6, 7) are selectively obtained starting from one simple benzimidazole-based ligand and square-planar palladium(II) ions, either by direct anion-adaptive self-assembly or induced-fit transformations. Hydrogen-bonding interactions between the inner surface of the macrocycles and the anionic guests dictate the shape and size of the product. A comprehensive induced-fit transformation map across all the M
L
species is drawn, with a representative reconstitution process from Pd
L
to Pd
L
traced in detail, revealing a gradual ring-shrinking mechanism. We envisage that these macrocyclic molecules with adjustable well-defined hydrogen-bonding pockets will find wide applications in molecular sensing or catalysis.
Chiral luminescent lanthanide-organic cages have many potential applications in enantioselective recognition, sensing, and asymmetric catalysis. However, due to the paucity of structures and their ...limited cavities, host-guest chemistry with lanthanide-organic cages has remained elusive so far. Herein, we report a guest-driven self-assembly and chiral induction approach for the construction of otherwise inaccessible Ln
L
-type (Ln = lanthanide ions, i.e., Eu
, Tb
; L = ligand) tetrahedral hosts. Single crystal analyses on a series of host-guest complexes reveal remarkable guest-adaptive cavity breathing on the tetrahedral cages, reflecting the advantage of the variation tolerance on coordination geometry of the f-elements. Meanwhile, noncovalent confinement of pyrene within the lanthanide cage not only leads to diminishment of its excimer emission but also facilitates guest to host energy transfer, opening up a new sensitization window for the lanthanide luminescence on the cage. Moreover, stereoselective self-assembly of either Λ
- or Δ
- type Eu
L
cages has been realized via chiral induction with
/
-BINOL or
/
-SPOL templates, as confirmed by NMR, circular dichroism (CD), and circularly polarized luminescence (CPL) with high dissymmetry factors (
) up to ±0.125.
Multivalent cooperativity plays an important role in the supramolecular self-assembly process. Herein, we report a remarkable cooperative enhancement of both structural integrity and metal ion ...selectivity on metal-organic M
L
tetrahedral cages self-assembled from a tris-tridentate ligand (L
) with a variety of metal ions spanning across the periodic table, including alkaline earth (Ca
), transition (Cd
), and all the lanthanide (Ln
) metal ions. All these M
L
cages are stable to excess metal ions and ligands, which is in sharp contrast with the tridentate (L
) ligand and bis-tridentate (L
) ligand bearing the same coordination motif as L
. Moreover, high-precision metal ion self-sorting is observed during the mixed-metal self-assembly of tetrahedral M
L
cages, but not on the M
L
counterparts. Based on the strong cooperative metal ion self-recognition behavior of M
L
cages, a supramolecular approach to lanthanide separation is demonstrated, offering a new design principle of next-generation extractants for highly efficient lanthanide separation.
Luminescent lanthanide‐containing compounds have a lot of stimulating applications. However, the fine‐tuning of the optical properties of multi‐nuclear lanthanide edifices is still a big challenge. ...We report here the coordination self‐assembly of a group of bright luminescent lanthanide organic polyhedra (LOPs) with record high emission quantum yields, by using two fully‐conjugated ligands featuring the triazole‐pyridine‐amido (tpa) chelating moiety, easily‐accessible from the “Click” reaction. The self‐assembled LOPs are characterized by NMR spectroscopy, high‐resolution ESI‐TOF‐MS, and X‐ray crystallography. Interestingly, inter‐metal energy transfer (ET) is confirmed on the mixed‐lanthanide polyhedral molecules, though the metal centers are separated nearly 2 nm apart. A feasible ratiometric luminescent thermometer, with work range from cryogenic to physiological temperatures, has been demonstrated with the mixed Eu/Tb LOPs. We envisage these molecular‐level bright luminescent LOPs have great application potential in displaying, labelling/imaging, up‐conversion materials etc.
Red hot! A group of bright luminescent lanthanide organic polyhedra (LOPs) with record‐high emission quantum yields are developed. A feasible ratiometric luminescent thermometer, with working range from cryogenic to physiological temperatures, has been demonstrated with the mixed Eu/Tb LOPs.
Supramolecular cages/vesicles in biology display sophisticated structures and functions by utilizing a few types of protein subunit quasi‐equivalently at distinct geometrical locations. However, ...synthetic supramolecular cages still lack comparable complexity to reach the high levels of functionality found in natural systems. Herein we report the self‐assembly of giant pentagonal supramolecular prisms (molecular weight >50 kDa) with tetratopic pyridinyl subunits serving different geometrical roles within the structures, and their packing into a novel superstructure with unexpected three‐fold rotational symmetry in a single two‐dimensional layer of crystalline state. The formation of these complicated structures is controlled by both the predetermined angles of the ligands and the mismatched structural tensions created from the multi‐layered geometry of the building blocks. Such a self‐assembly strategy is extensively used by viruses to increase the volume and complexity of capsids and would provide a new approach to construct highly sophisticated supramolecular architectures.
Giant supramolecular pentagonal prisms with pumpkin‐like shapes are self‐assembled with subunits in geometrically non‐equivalent locations. These 5‐fold symmetric solids are able to pack into a new type of 2D periodic superstructure in the (0,0,1) crystal plane with three‐fold rotational symmetry via lateral‐edge to lateral‐edge contacting arrangement of the prisms.
Russian dolls: Two covalently tethered, curved bispyridinyl ligands and PdII ions have been shown to self‐assemble into a sphere‐in‐sphere complex (6.3 nm in diameter; see X‐ray structure). The two ...ligands did not form heteroleptic mixed complexes, but instead assembled into two distinct homogeneous M12L24 cuboctahedra, reminiscent of a double‐shell viral capsid.
Controllable arrangement of different ligands in a single assembly will not only bring increased complexity but also offers a new route to fine‐tune the function of the designed architecture. We ...report here a combinatorial self‐assembly with enPd(NO3)2 and three different ligands (L1–3), which gave rise to a family of six palladium‐organic cages (C1‐6) with systematically varied shapes and cavities, including three new heteroleptic (Pd5L12L2, Pd5L12L3, Pd4L2L3), one new homoleptic (Pd4L32) cages, and two known homoleptic (Pd6L14, Pd4L22) cages. Emergent functions due to the fusion of two half cavities on the heteroleptic cages from their parent homoleptic cages have been observed: the heteroleptic cages can form ternary complexes by co‐encapsulation of both aromatic and aliphatic guests, while their homoleptic counterparts can only form binary complexes. Such a forced co‐encapsulation effect endows the heteroleptic cages with enhanced catalytic power for the Knoevenagel condensation.
A combinatorial self‐assembly approach gives rise to a family of palladium‐organic cages featuring systematically fine‐tuned shapes and cavities. Emergent guest‐binding and catalytic functions were observed that are due to the fusion of two half cavities on the heteroleptic cages from their parent homoleptic cages.
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