Search

Controlled self-assembly of predetermined multi-nuclear lanthanide organic polyhedra (LOPs) still presents a challenge, primarily due to the unpredictable coordination numbers and labile coordination geometries of lanthanide ions. In this study, through introducing triazole-based chelates to increase the chelating angle of C2-symmetric linear ligands and stabilize the coordination geometry of Eu(III) centers, M4L6-type (M = EuIII, L = ligand) tetrahedra were efficiently synthesized, especially a biphenyl-bridged ligand which is well known to form M2L3-type helicates. A series of LOPs were formed and characterized by high-resolution electrospray ionization time-of-flight mass spectroscopy (ESI-TOF-MS) and X-ray crystallography. Moreover, the europium complexes exhibit bright emission (luminescence quantum yield up to 42.4%) and circularly polarized luminescence properties (‖glum‖ up to 4.5 × 10−2). This study provides a feasible strategy for constructing multi-nuclear luminescent LOPs towards potential applications. [ABSTRACT FROM AUTHOR]

Well-defined 3d–4f heterometallic supramolecular architectures have attracted attention because of their applications in the field of luminescence and magnetism. However, covalent metallo-supramolecular discrete complexes, decorated with hetero-metallic vertices, have never been reported because of the difficulties in design and control. Herein, we report a series of covalent metallo-supramolecular discrete complexes with 3d–4f vertices synthesized by hierarchical subcomponent self-assembly of tris(2-aminoethyl)amine, 2,6-diformyl-p-cresol, and lanthanide ions (Ln) with different amines and transition metal ions. The programmable self-assembly process results in the formation of triple-stranded hetero-metallic covalent organic discrete complexes, namely 3a–3c-(Ln, Zn) (Ln = SmIII, EuIII, DyIII, YbIII and LuIII) and 3a′-(Dy, Co), which are characterized by nuclear magnetic resonance (NMR) analysis, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and single-crystal X-ray analysis. Photophysical investigations disclose that the organic skeleton of 3a-(Ln, Zn) exhibits an excellent sensitizing ability toward SmIII, EuIII, and YbIII ions, displaying characteristic luminescence emission in both the visible and near-infrared (NIR) regions. AC susceptibility measurements of 3a′-(Dy, Co) reveal the frequency-independent performance under zero dc field, suggesting the absence of slow relaxation of magnetization. This work offers a new approach for the fabrication of discrete metallic covalent architectures with 3d–4f vertices. [ABSTRACT FROM AUTHOR]

Brønsted-base active sites on a Pd4L2 cage facilitates enhanced catalytic efficiency, wide substrate scope and high turnover number (TON) for the one-pot photooxidation/Knoevenagel condensation reaction under mild conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Understanding the kinetic process during the self‐assembly and chiral amplification of metal‐organic polyhedra (MOPs) is critical for the rational preparation of chiral MOPs. Herein, we report the ionic radius dependent kinetic processes for the self‐assembly and chiral amplification of Ln4L4‐type (Ln, Lanthanides; L, ligand) lanthanide tetrahedral cages. The chiral Eu4(LR)4 tetrahedral cage is structurally characterized by nuclear magnetic resonance (NMR), electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS), and single crystal X‐ray diffraction. Kinetic study on the stereo‐controlled self‐assembly of circularly polarized luminescence (CPL)‐active Ln4(LR)4 (Ln = LaIII, PrIII and EuIII) tetrahedra manifests that the larger ionic radius of Ln leads to faster assembly rates. Mixed‐ligand cage assembly experiments with chiral LR/S, achiral Lac and Ln (1 : 3 : 4 molar ratio) reveal that the self‐assembly and chiral amplification occur synchronously for the LaIII and PrIII cages, while two distinct steps, i.e., first self‐assembly and then chiral amplification, are observed for the EuIII cage. Such distinct kinetic behavior is attributed to different ligands exchange rates among the mixed‐ligand Ln4L4 cages. This work provides fundamental guidance for fabrication and property‐optimization of chiral lanthanide‐based molecular materials. [ABSTRACT FROM AUTHOR]

Organic pollutants cause severe environmental problems because of their damage to human health and ecological systems. Photocatalytic degradation of persistent organic pollutants is of great importance to address these hazards. Herein, we report a lanthanide organic polyhedra‐based hybrid material Gd8L12⊂MSN with the capability of photocatalytic dye degradation. Gd8L12⊂MSN was prepared by embedding the Gd8L12 complex into mesoporous silica nanoparticles (MSNs) using a "ship‐in‐a‐bottle" strategy. Photocurrent response tests revealed that this hybrid material is a potential semiconductor and could generate a rapid and steady photocurrent upon irradiation. Further dye degradation experiments indicated that it could photocatalyze the degradation of familiar organic dyes. Thereinto, compared with the critical Gd8L12 complex, the hybrid material exhibited an acceleration of 2.4 times and realized reusability. This not only offers a potential advanced photocatalyst for degrading persistent organic pollutants, but also provides a strategy for the application of supramolecular materials in environmental science. [ABSTRACT FROM AUTHOR]

We designed and synthesized a semi-rigid bis-tridentate ligand L which could undergo a trans-to-cis conformational transition when coordinated onto lanthanum ions through the rotation of the single bond on the central terphenyl bridge. By adjusting the metal/ligand ratio, a single-ligand bridged dinuclear complex La2L3 and an infinitely extending two-dimensional layered metal organic polymer (La2L2)n can be obtained. Through the induction of the chiral auxiliary ligand G R/S , these two achiral assemblies could both be transformed into the chiral mononuclear three-component complex LaLG R/S . In addition, we also realized a linear ee sensing for the auxiliary ligand by induced circular dichroism. [ABSTRACT FROM AUTHOR]

Artificial hosts with rich conformational dynamics are attractive to supramolecular chemists due to their adaptive guest‐binding properties and enzyme‐like catalytic functions. We report here the adaptive self‐assembly and host‐guest catalysis of a new water‐soluble organo‐palladium host (Pd2L2) built from a pyridinium‐bonded macrocyclic ligand (L) and cis‐blocked palladium corners (Pd). While the direct self‐assembly of L with Pd gives rise to a dynamic mixture of products, both neutral polyaromatic hydrocarbons and an anionic polyoxometalate cluster (W10O324−) can template the dominant formation of the Pd2L2 host. Guest‐adaptive conformational changes and induced‐fit cavity deformation of the Pd2L2 host have been clearly observed in the crystal structures. Moreover, the installation of the electron‐rich W10O324− cluster within the cationic redox‐active host (W10O32⊂Pd2L2) facilitates the efficient and selective C−H photooxidation of toluene derivatives to aldehyde products under mild conditions, thus representing an ideal platform for green supramolecular catalysis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A series of lanthanide-organic pincer hosts were synthesized, which showed allosteric-controlled metal ion binding selectivities due to the lanthanide-induced subtle changes of the central vacant binding site. [ABSTRACT FROM AUTHOR]

We report here a simple but efficient "ship-in-a-bottle" synthetic strategy for increasing the stability and luminescence performance of LOPs by embedding them into mesoporous silica nanoparticles (MSNs). Three types of hybrid materials, i.e. Eu8L12@MSNs, Eu8L12@MSNs-NH2 and Eu8L12@MSNs-biotin, have been prepared and characterized by FT-IR, TGA, SEM and TEM. Photo-optical measurements confirmed that the photoluminescence quantum yields in water have been greatly improved from 5.50% for pristine Eu8L12 to 44.04% for Eu8L12@MSNs-biotin, along with fast disassembly for the former and the optical performance has been maintained for the latter under acidic conditions (pH = 4). Moreover, compared to Eu8L12, Eu8L12@MSNs and Eu8L12@MSNs-NH2, the biotin-modified hybrid material Eu8L12@MSNs-biotin has exhibited much enhanced fluorescence-imaging ability toward the MDA-MB-231 human breast cancer cells, with significantly reduced dosage of the complex. Our work provides a useful strategy for the functionalization of multinuclear lanthanide organic assemblies toward their biosocial applications. [ABSTRACT FROM AUTHOR]

Spin-crossover (SCO) active compounds have received much attention due to their potential application in molecular devices. Herein, a family of solvent-free FeII compounds, formulated as (A)2[FeL2], (H2L = pyridine-2,6-bi-tetrazolate, A = (Me)4N+1, Et2NH2+2, iPr2NH2+3 and iPrNH3+4), were synthesized and characterized. Single-crystal X-ray diffraction studies reveal that 1–4 are all supramolecular frameworks containing the same [FeL2]2− center, which is arranged into two packing modes via inter-molecular interactions, that is, a 3D architecture in 1 and 1D chain in 2–4. The spin states of 1–4 at different temperatures are assigned on the basis of the single-crystal X-ray diffraction data. Solid state magnetic investigations indicate that 1 and 4 exhibit a low spin state (below 350 K) and high spin state (2–400 K), respectively. 2 and 3 display clear SCO behavior in the measured temperature, but with different profiles and critical temperatures. 2 undergoes a complete gradual SCO with a critical temperature of T1/2 = 260 K. 3 has an abrupt near room temperature transition between T1/2 cooling = 278 K and T1/2 warming = 286, centered at 282 K (9 °C). This study reveals the importance of organic cations in the modulation of SCO behavior and offers a new insight for the design of SCO compounds with near room temperature spin transitions. [ABSTRACT FROM AUTHOR]

Herein, we report a comprehensive study on the lanthanide‐directed coordination self‐assembly with two bis‐tetradentate acylhydrazone ligands H4L1 and H4L2. Multifarious outcomes, which are base‐ and metal‐dependent, were revealed by NMR, ESI‐TOF‐MS and X‐ray crystallography. In the absence of base, bent H4L1 was assembled into dinuclear double‐strand helicate Ln2(H2L1)2 by partially‐deprotonated assembly with La, Sm or Eu, while trinuclear Ln3(H2L1)3 with Yb or Lu. For linear H4L2, infinite 1D zig‐zag metal‐organic polymeric chain (Ln2H2L2)n was obtained. However, complete deprotonated L1 and L2 assembled into discrete trinuclear Ln3(L1/2)3 and tetranuclear Ln4(L1/2)4 macrocyclic structures under the basic condition. For these, there are multiple possible isomers coexisting in the solution which were enumerated and simulated with molecular mechanic modeling. Visible‐light sensitized NIR emissions on the Yb complexes have been observed, endowing them potential application in photofunctional materials. [ABSTRACT FROM AUTHOR]

Water-stable anionic Ln2L2-type (Ln = LaIII and EuIII) lanthanide–organic macrocycles have been constructed by deprotonation self-assembly of a bis-tridentate ligand consisting of two 2,6-bis-(1,2,4-triazole)-pyridine chelation arms bridged by a dibenzofuran chromophore, of which the luminescent Eu2L2 macrocycle can be used for enantiomeric excess (ee) detection toward pybox-type chiral ligands and selective colorimetric sensing of omethoate (OMA) in water. [ABSTRACT FROM AUTHOR]

Molecular cages have attracted great attention because of their fascinating topological structures and well‐defined functional cavities. These discrete cages were usually fabricated by coordination assembly approach, a process employing directional metal‐ligand coordination bonds due to the nature of the divinable coordination geometry and the required lability to encode dynamic equilibrium/error‐correction. Compared to these coordination molecular cages with mononulcear metal‐nodes, an increasing number of molecular cages featuring dinuclear and then polynuclear metal‐cluster nodes have been synthesized. These metal‐cluster‐based coordination cages (MCCCs) combine the merits of both metal clusters and the cage structure, and exhibit excellent performances in catalysis, separation, host‐guest chemistry and so on. In this review, we highlight the syntheses of MCCCs and their potential functions that is donated by the metal‐cluster nodes. [ABSTRACT FROM AUTHOR]

By introduction of a new Fe(L1)2 spin-crossover (SCO) unit into the polynuclear system, a nano-scale Fe4(L2)4 molecular square architecture is designed through coordination-directed self-assembly strategy. Both the mononuclear Fe(L1)2 and tetranuclear Fe4(L2)4 complexes have been structurally confirmed by 1H nuclear magnetic resonance (NMR), electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and temperature-dependent single crystal X-ray diffraction studies. Variable-temperature magnetic susceptibility measurements reveal the presence of an abrupt SCO behavior with a thermal hysteresis width of 4 K for Fe(L1)2. By clear contrast, Fe4(L2)4 undergoes a gradual spin transition behavior with enlarged thermal hysteresis width and higher spin transition temperature. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We report here a guest‐reaction‐induced mitosis‐like host transformation from a known Pd4L2 cage 1 to a conjoined Pd6L3 twin‐cage 2 featuring two separate cavities. The encapsulation of 1‐hydroxymethyl‐2‐naphthol (G1), a known ortho‐quinone methide (o‐QMs) precursor, within the hydrophobic cavity of cage 1 is found crucial to realize the cage to twin‐cage conversion. Confined G1 molecules within the nanocavity undergo self‐coupling dimerization reaction to form 2,2′‐dihydroxy‐1,1′‐dinaphthylmethane (G2) which then triggers the cage to twin‐cage mitosis. The same conversion also proceeds, in a much faster rate, via the direct templation of G2, confirming the induced‐fit transformation mechanism. The structure of the (G2)2⊂2 host–guest complex has been established by X‐ray crystallographic study, where cis‐ to trans‐ conformational switch on one bridging ligand is revealed. [ABSTRACT FROM AUTHOR]

A post-synthetic transmetallation self-assembly strategy was developed for the preparation of near infrared (NIR) emitting Yb8L6 cubes, which could not be synthesized through direct metal–ligand assembly procedures. Metal-adaptive critical structural transformations from La6L3 triangular prism to Ln8L6 cubes were observed along the lanthanide series, the latter of which showed size-selective guest binding behaviour toward poly-aromatic hydrocarbon (PAH) molecules. [ABSTRACT FROM AUTHOR]

A stereocontrolled self-assembly of 5d/4f heterometal–organic macrocycles has been realized by a post-assembly chiral auxiliary approach. Interligand π–π stacking interactions promoted chiral transfer from point-chirality of the auxiliary ligand to metal centers and then the helicates to produced CD and CPL active europium assemblies, facilitating a feasible enantiomeric excess determination by induced chiroptical signals. [ABSTRACT FROM AUTHOR]