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Innovation in the development of electrochemical energy storage methods is essential if these technologies are to meet the variable needs of the electrical grid. Nonaqueous redox flow batteries represent an underdeveloped area of research in energy storage—one which has seen a recent spike in interest owing to the potential for modular, energy-dense electrochemical energy conversion. Here, we summarize our recent work, focused on the design of polyoxovanadate-alkoxide clusters [V6O7(OR)12] as a new class of charge carrier for nonaqueous energy storage. The synthetic strategies we have employed, including homoleptic ligand substitution, selective ligand functionalization, and heterometal installation, demonstrate the flexibility of this hexametalate platform, and result in significant improvement of molecular properties with relevance to flow battery energy density. The identified homoleptic surface modifications (substituting R = CH3 for R = C2H5) to the polyoxovanadate-alkoxide scaffold yield an increase in stable operating voltage window (from 0.6 V to 1.8 V), as well as an increase in the stoichiometric number of electrons that can be stored at each battery electrode (from 1 to 2). Targeted functionalization at the cluster surface with an ether-based ligand affords [V6O7(OC2H5)9(OCH2)3CCH2OC2H4OCH3], which demonstrates a 12-fold increase in solubility over its homoleptic congener, from 0.05 to 0.60 M in acetonitrile. The substitution of a titanium center into the hexametalate core to generate [V5TiO6(OCH3)13]− further increases the voltage window to 2.3 V, as new heterometal-based redox events are introduced to the profile. Through these studies, we have gained valuable insights into the molecular parameters that determine the energy storage capabilities of multimetallic charge carriers. Collectively, our results highlight new opportunities for polynuclear charge carriers, and emphasize the critical role that synthetic inorganic chemistry plays in the development of effective nonaqueous redox flow battery technologies. [ABSTRACT FROM AUTHOR]

Here we report on a scanning tunnelling microscopy (STM) investigation on the self-assembly of C 3 - and C 2 -symmetric molecules at the solution/graphite interface. 1,3,5-tris(( E )-2-(pyridin-4-yl)vinyl)benzene and 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethane are used as model systems. These molecules displayed a concentration dependent self-assembly behaviour on graphite, resulting in highly ordered supramolecular structures, which are stabilized jointly by van der Waals substrate-adsorbate interactions and in-plane intermolecular H-bonding. Denser packing is obtained when applying a relatively high concentration solution to the basal plane of the surface whereas a less dense porous network is observed upon lowering the concentration. We show that the molecular conformation does not influence the stability of the self-assembly and a twisted molecule can pack into dense and porous architectures under the concentration effect. [ABSTRACT FROM AUTHOR]

Non-aqueous redox flow batteries (naRFBs) are promising candidates as high-capacity energy storage devices. Although the wide redox windows associated with the organic solvents used in naRFBs are useful to realize high open circuit voltages, the low solubilities of electrolytes often minimize the energy densities. Strategies have emerged to increase the concentration of active materials employed in naRFBs; however, the dilute conditions typically associated with chronoamperometry and voltammetric experiments are orders of magnitude lower than those found in a working RFB. The electrochemical behavior of non-aqueous electrolytes may differ at high concentrations due to changes in solvation structure, aggregation, solution resistance, and mass transport, which in turn affect the overall cell performance. Accordingly, we studied a series of naRFB systems using ferrocene/TEMPO as a posolyte, and cobaltocenium hexafluorophosphate/N-methylphthalimide as a negolyte, to investigate the effect of concentration on charge-discharge profiles. Cycling studies were performed with four combinations of the above-mentioned catholyte and anolyte materials. Concentration regimes were explored ranging from 10 mM to 1 M depending on the maximum solubility of a given active species. The results indicate that cycling behaviors are concentration dependent. Coulombic efficiencies and voltage efficiencies are calculated for each system. In addition, it was observed that the specific combination of catholyte/anolyte also affects the charge-discharge profiles and that membrane crossover and fouling is a major contributor to performance losses. [ABSTRACT FROM AUTHOR]

We present the formation of a series of chiral metallacycles and metallacages by the use of a BINOL-derived dicarboxylate as a donor that is capable of affording a variety of coordination angles between its two Lewis basic sites. Two squares, two rhomboids, two tetragonal prisms, and one hexagonal prism were successfully formed when the chiral dicarboxylate donor self-assembled with one of four ditopic Pt(II) complexes, including two bimetallic 180° Pt-based acceptors, a 120° bimetallic Pt-based acceptor, and a 90° mononuclear Pt-based acceptor. Their structures were well characterized by 31P{1H} NMR, ESI-MS, CD, and optical rotation analyses. [ABSTRACT FROM AUTHOR]

The article focuses on developments in chemistry of metallacycles and metallacages through metal-ligand coordination. Topics include approaches for structural chemistry of metallacycles including edge-and face-direct assembly, catenanes and covalent stabilization; functional use of metallacycles such as sensors and catalysis; and chemical reaction showing tetranuclear metallacycles.

Light-emitting materials, especially those with tunable wavelengths, attract considerable attention for applications in optoelectronic devices, fluorescent probes, sensors and so on. Many species evaluated for these purposes either emit as a dilute solution or on aggregation, with the former often self-quenching at high concentrations, and the latter falling dark when aggregation is disrupted. Here we preserve emissive behaviour at both low- and high-concentration regimes for two discrete supramolecular coordination complexes (SCCs). These tetragonal prismatic SCCs are self-assembled on mixing a metal acceptor, Pt(PEt3)2(OSO2CF3)2, with two organic donors, a pyridyl-decorated tetraphenylethylene and one of two benzene dicarboxylate species. The rigid organization of these fluorescence-active ligands imparts an emissive behaviour to dilute solutions of the resulting assemblies. Furthermore, on aggregation the prisms exhibit variable-wavelength visible-light emission, including rare white-light emission in tetrahydrofuran. The favourable photophysical properties and solvent-dependent aggregation behaviour provide a means to tune emission wavelengths. [ABSTRACT FROM AUTHOR]

Oligo(ethylene glycol) (OEG)-decorated supramolecular assemblies are distinguished by their neutral character and macroscopic temperature-sensitive phase transition behavior. OEG functionalization is an emerging strategy to obtain thermoresponsive macrocyclic amphiphiles, although known methods organize the hydrophilic and hydrophobic segments by covalent bonding. Coordination-driven self-assembly offers an alternative route for organizing OEG-functionalized precursors into nanoscopic architectures, resulting in well-defined metallacycle cores surrounded by hydrophilic scaffolds to impart overall amphiphilic character. Here a tri(ethylene glycol)-functionalized thermosensitive amphiphilic metallacycle was prepared with high efficiency by means of the directional-bonding approach. The ensembles thus formed showed good lower critical solution temperature behavior with a highly sensitive phase separation and excellent reversibility. Moreover, the clouding point decreased with increasing metallacycle concentration and addition of K+. [ABSTRACT FROM AUTHOR]

Review: 93 refs. [ABSTRACT FROM AUTHOR]

Review: 367 refs. [ABSTRACT FROM AUTHOR]

Energy-relevant small molecule activations and related processes are often multi-electron in nature. Ferrocene is iconic for its well-behaved one-electron chemistry, and it is often used to impart redox activity to self-assembled architectures. When multiple ferrocenes are present as pendant groups in a single structure, they often behave as isolated sites with no separation of their redox events. Herein, we study a suite of molecules culminating in a self-assembled palladium(II) truncated tetrahedron (TT) with six pendant ferrocene moieties using the iron(III/II) couple to inform about the electronic structure and, in some cases, subsequent reactivity. Notably, although known ferrocene-containing metallacycles and cages show simple reversible redox chemistry, this TT undergoes a complex multi-step electrochemical mechanism upon oxidation. The electrochemical behavior was observed by voltammetric and spectroelectrochemical techniques and suggests that the initial Fc-centered oxidation is coupled to a subsequent change in species solubility and deposition of a film onto the working electrode, which is followed by a second separable electrochemical oxidation event. The complicated electrochemical behavior of this self-assembly reveals emergent properties resulting from organizing multiple ferrocene subunits into a discrete structure. We anticipate that such structures may provide the basis for multiple charge separation events to drive important processes related to energy capture, storage, and use, especially as the electronic communication between sites is further tuned. [ABSTRACT FROM AUTHOR]

The chemistry of zirconium-based metal-organic polyhedra (ZrMOPs) is often limited by their poor solubilities. Despite their attractive features—including high yielding and facile syntheses, predictable topologies, high stability, and tunability—problematic solubilities have caused ZrMOPs to be under-studied and under-applied. Although these cages have been synthesized with a wide variety of carboxylate-based bridging ligands, we explored a new method for ZrMOP functionalization via node-modification, which we hypothesized could influence solubility. Herein, we report ZrMOPs with benzyl-, vinylbenzyl-, and trifluoromethylbenzyl-pendant groups decorating cyclopentadienyl moieties. The series was characterized by 1H/19F NMR, high-resolution mass spectrometry, infrared spectroscopy, and single-crystal X-ray diffraction. The effects of node functionalities on ZrMOP solubility were quantified using inductively coupled plasma mass spectrometry. Substitution caused a decrease in water solubility, but for certain organic solvents, e.g. DMF, solubility could be enhanced by ∼20×, from 16 μM for the unfunctionalized cage to 310 μM for the vinylbenzyl- and trifluoromethylbenzyl-cages. [ABSTRACT FROM AUTHOR]

We report the electrocatalytic Oxygen Reduction Reaction on a rigid Co(II) porphyrin prism scaffold bridged by Ag(I) ions. The reactivity of this scaffold differs significantly from previous prism catalysts in that its selectivity is similar to that of monomer (∼35% H2O) yet it displays sluggish kinetics, with an order of magnitude lower ks of ∼0.5 M−1 s−1. The deleterious cofacial effect is not simply due to metal–metal separation, which is similar to our most selective prism catalysts. Instead we conclude the structural rigidity is responsible for these differences. [ABSTRACT FROM AUTHOR]

Herein we report the first study of the oxygen reduction reaction (ORR) catalyzed by a cofacial porphyrin scaffold accessed in high yield (overall 53%) using coordination-driven self-assembly with no chromatographic purification steps. The ORR activity was investigated using chemical and electrochemical techniques on monomeric cobalt(II) tetra(meso-4-pyridyl)porphyrinate (CoTPyP) and its cofacial analogue [Ru8(η6-iPrC6H4Me)8(dhbq)4(CoTPyP)2][OTf]8 (Co Prism) (dhbq = 2,5-dihydroxy-1,4-benzoquinato, OTf = triflate) as homogeneous oxygen reduction catalysts. Co Prism is obtained in one self-assembly step that organizes six total building blocks, two CoTPyP units and four arene-Ru clips, into a cofacial motif previously demonstrated with free-base, Zn(II), and Ni(II) porphyrins. Turnover frequencies (TOFs) from chemical reduction (66 vs 6 h-1) and rate constants of overall homogeneous catalysis (kobs) determined from rotating ring-disk experiments (1.1 vs 0.05 h-1) establish a cofacial enhancement upon comparison of the activities of Co Prism and CoTPyP, respectively. Cyclic voltammetry was used to initially probe the electrochemical catalytic behavior. Rotating ring-disk electrode studies were completed to probe the Faradaic efficiency and obtain an estimate of the rate constant associated with the ORR. [ABSTRACT FROM AUTHOR]

Herein, we describe the synthesis of tetraphenyl -ethylene (TPE)-based di-Pt(ll) acceptors as shown by X-ray analysis, which are subsequently used to construct pure TPE-based 2D hexagonal metallacycles and 3D drumlike metallacages with three different counteranions via coordination-driven self-assembly.The metallacycles possess alternating TPE donor and acceptor 6 units that arrange 12 pendant phenyl rings along the outer perimeter that provide the basis for the observed aggregation induced emission (ALE) behavior. The metallacages are similarly 2 constructed from TPE-based building blocks, specifically two donors and four acceptors, resulting in eight freely rotating phenyl rings decorating the prismatic core. The fluorescence of these cages in dilute solution is intensified when hexane is added to CH2C12 solutions, indicative of aggregation-induced enhanced emission (ALEE). The influence of the counteranions on the photophysics of the assemblies was investigated. The molar absorption coefficients (ε), fluorescence emission intensities, and quantum yield (ΦF) values of the SCCs with different counteranions in CH2C12 follow the order PF6- > OTf- > N03-. The same trend also applies to the AIE characteristics of the SCCs in the aggregated state. The metal-organic materials developed here not only enrich a newly emerging library of self-assembly AIE metallacycles and cages that are promising candidates for turn-on fluorescent sensors and advanced optical devices but also provide an understanding of how structural factors affect the photophysics of AIE-active SCCs. [ABSTRACT FROM AUTHOR]

Here we present a method for the construction of functionalizable supramolecular polymers by controlling three orthogonal interactions within a single system: (i) coordination-driven self-assembly; (ii) H-bonding; and (iii) host--guest interactions between crown ether and dialkylammonium substrates. Three unique molecules constitute the supramolecular construct, including a 2-ureido-4-pyrimidinone (UPy)-functionalized rigid dipyridyl donor and a complementary organo-platinum(II) acceptor decorated with a crown ether moiety that provide the basis for self-assembly and polymerization. The final host--guest interaction is demonstrated by using one of two dialkylammonium molecules containing fluorophores that bind to the benzo-21-crown-7 (B21C7) groups of the acceptors, providing a spectroscopic handle to evaluate the functionalization. An initial coordination-driven self-assembly yields hexagonal metallacycles with alternating UPy and B21C7 groups at their vertices. The assembly does not interfere with H-bonding between the UPy groups, which link the discrete metallacycles into a supramolecular network, leaving the B21C7 groups free for functionalization via host--guest chemistry. The resultant network results in a cavity-cored metallogel at high concentrations or upon solvent swelling. The light-emitting properties of the dialkylammonium substrates were transferred to the network upon host-guest binding. This method is compatible with any dialkylammonium substrate that does not disrupt coordination nor H-bonding, and thus, the unification of these three orthogonal interactions represents a simple yet highly efficient strategy to obtain supramolecular polymeric materials with desirable functionality. [ABSTRACT FROM AUTHOR]

Coordination-drivenself-assembly can be used to construct metallacyclesdecorated with saccharide functionalities by combining organoplatinumacceptor building blocks with glycosylated dipyridyl donors. We describehere the synthesis of a suite of donors encoded with 120° directionality.The 1,3-bis(pyridin-4-ylethynyl)benzene cores contain one of fourpendant saccharide groups, resulting in a glucose-, galactose-, mannose-,and lactose-variant. The angularity of these donors makes them suitablefor the self-assembly of [2 + 2] rhomboids and [3 + 3] hexagons containingtwo and three saccharide groups on combination with a 60 or 120°acceptor, respectively. The synthesis and characterization of eightsuch metallacycles are described, supported by multinuclear NMR andelectrospray mass spectrometry data that confirm clean, highly symmetricproducts with the expected stoichiometries of formation. This workillustrates the use of coordination-driven self-assembly to obtainnanoscopic metallacycles with biologically relevant functionalitiesin high yields and facile synthetic methods. [ABSTRACT FROM AUTHOR]

Among the many challenges in medicine, the treatment and cure of cancer remains an outstanding goal given the complexity and diversity of the disease. Nanotheranostics, the integration of therapy and diagnosis in nanoformulations, is the next generation of personalized medicine to meet the challenges in precise cancer diagnosis, rational management and effective therapy, aiming to significantly increase the survival rate and improve the life quality of cancer patients. Different from most conventional platforms with unsatisfactory theranostic capabilities, supramolecular cancer nanotheranostics have unparalleled advantages in early-stage diagnosis and personal therapy, showing promising potential in clinical translations and applications. In this review, we summarize the progress of supramolecular cancer nanotheranostics and provide guidance for designing new targeted supramolecular theranostic agents. Based on extensive state-of-the-art research, our review will provide the existing and new researchers a foundation from which to advance supramolecular cancer nanotheranostics and promote translationally clinical applications. [ABSTRACT FROM AUTHOR]

A series of new polymer-inorganic composites has been synthesized from poly(amic acid) (PAA) and various M-MOF-74 (M = Mg, Mn, Co, Ni, Zn) frameworks using a postsynthetic ligand exchange strategy, wherein ligand moieties built into the PAA backbone are exchanged with MOF-bound ligands. The reaction is monitored by UV-vis spectroscopy in order to compare exchange rates for different metal ions, and the resulting composites are characterized by powder X-ray diffraction and scanning electron microscopy. This method of polymer-ligand exchange (PLE) hybridization has only been previously demonstrated using Zn2+-carboxylate and Zn2+-imidazolate frameworks; therefore, this work further reveals the versatility of PLE by showing that exchange is possible for several additional metal ions, as well as frameworks containing 2,5-dihydroxyterephthalate ligands. [ABSTRACT FROM AUTHOR]

Abstract: We report a suite of coordination‐driven self‐assembled prisms for heterogeneous electrocatalytic oxygen reduction (ORR) differing in the molecular clips linking two porphyrin faces in a cofacial arrangement. ORR activities and selectivities of monomeric CoTPyP along with cofacial prisms Ox‐Co, Oxa‐Co, and Benzo‐Co were probed using cyclic voltammetry and rotating ring‐disk techniques. All species were immobilized as heterogeneous catalysts on glassy carbon electrodes using a Nafion ink method. The selectivities of Ox‐Co, Oxa‐Co, and Benzo‐Co prisms towards H2O as determined by RRDE were 87, 97, and 75 %, respectively. The current density of the Oxa‐Co plateaus at five times that of Pt/C when normalized per Co/Pt. The high synthetic yield (79 %), competitive overpotential (η ≈800 mV) and high selectivity (%H2O ≈97 %) of the Oxa‐Co highlights how self‐assembly can be used to address multi‐electron multi‐proton transformations using polynuclear catalysts. [ABSTRACT FROM AUTHOR]

Discrete metal–organic polyhedra (MOPs) containing copper(ii), palladium(ii), and iron(ii) nodes were synthesized as fillers for mixed-matrix materials (MMMs) with a polyvinylidine fluoride (PVDF) polymer phase and contrasted against an MMM containing a metal–organic framework, MOF-5. When a given MOP was soluble in the precursor solutions, the resulting MMMs were thin, flexible, and homogeneous based on microscopy and SEM imaging. Analogous MMM formation using either insoluble MOPs or the inherent insoluble MOF-5 showed a higher degree of phase separation and inhomogeneity. Even when a MOP was not fully soluble, a significant particle size decrease was observed in contrast to the MOF-5 materials wherein the crystallites remained largely intact. This is a consequence of solubilizing the MOP fillers into the polymer solvent. The crystallinity and thermal stabilities of the MMMs were compared to pure PVDF using powder X-ray diffraction, and differential scanning calorimetry, indicating that the incorporation of MOPs both decreased overall crystallinity as well as increased thermal stability. In addition, MMMs containing PdMOP and FeMOP showed improved gas permeabilities relative to pure PVDF for H2, N2, CH4, and CO2, with the 10 wt% FeMOP membrane more selective for CO2 over N2 and H2. [ABSTRACT FROM AUTHOR]

Light-emitting supramolecular coordination complexes (SCCs) have been widely studied for applications in the chemical and biological sciences. Herein, we report the coordination-driven self-assembly of two highly emissive platinum(II) supramolecular triangles (1 and 2) containing BODIPY-based bridging ligands. The metallacycles exhibit favorable anticancer activities against HeLa cells (IC50 of 6.41 and 2.11 µM). The characteristic ~570 nm fluorescence of the boron dipyrromethene (BODIPY) moieties in the metallacycles permits their intracellular visualization using confocal microscopy. Additionally, the BODIPY fluorophore is an excellent photodynamic agent, making the metallacycles as ideal therapeutics for photodynamic therapy (PDT) and chemotherapy. In vitro studies demonstrate that the combination indexes against HeLa cells are 0.56 and 0.48 for 1 and 2, respectively, confirming their synergistic anticancer effect. More importantly, these SCCs also exhibit superior anticancer efficacy toward cisplatin-resistant A2780cis cell line by combining PDT and chemotherapy, showing promise in overcoming drug resistance. This study exploits a multicomponent approach to self-assembled metallacages that enables design of effective theranostic agents wherein the platinum acceptors are toxic chemotherapeutics and the BODIPY donors are imaging probes and photosensitizers. Since each piece may be independently tuned, i.e., Pt(II) polypyridyl fragment swapped for Pt(II) phosphine, the activity may be optimized without a total redesign of the system. [ABSTRACT FROM AUTHOR]

A reversible Fe3+/Fe2+ redox couple of an azamacrocyclic complex is evaluated as an electrolyte with a pH-tunable potential range for aqueous redox-flow batteries (RFBs). The FeIII complex is formed by 1,4,7-triazacyclononane (TACN) appended with three 2-methyl-imidazole donors, denoted as Fe(Tim). This complex exhibits pH-sensitive redox couples that span E1/2(Fe3+/Fe2+)=317 to −270 mV vs. NHE at pH 3.3 and pH 12.8, respectively. The 590 mV shift in potential and kinetic inertness are driven by ionization of the imidazoles at various pH values. The Fe3+/Fe2+ redox is proton-coupled at alkaline conditions, and bulk electrolysis is non-destructive. The electrolyte demonstrates high charge/discharge capacities at both acidic and alkaline conditions throughout 100 cycles. Given its tunable redox, fast electrochemical kinetics, exceptional stability/cyclability, this complex is promising for the design of aqueous RFB catholytes and anolytes that utilize the earth-abundant element iron. [ABSTRACT FROM AUTHOR]

The coordination of a bis(dipyrrin) ligand (LH2) to Re(CO)5Cl delivers a dirhenium salt that serves as a precursor to a dinuclear phosphine compound or as a component of a metallacycle when combined with 4,4'-bipyridine (bpy) to furnish a tetranuclear [{(CO)3Re}4L2(bpy)2] complex. The distorted nature of the metallacycle was determined by single-crystal X ray diffraction revealing that the Re-bpy-Re edges are twisted by approximately 119° and the Re-L-Re edges are twisted by approximately 88° from the idealized rectangular plane. The ReI metallacycle exhibits luminescence (λfluo. = 592 nm; λphos. = 731 nm) in CH2Cl2 at 77 K. [ABSTRACT FROM AUTHOR]

The emission of platinum-alkynyl complexes with terminal pyridyl moieties changes upon simple alkylation reactions. Due to growing interest in photovoltaics, photocatalysis, and light-emitting devices, understanding the nature of these changes is important to develop simple synthetic pathways for the rational design of photophysically active molecules. Herein, the choice of ligand isomer, methylation, and Pt-coordination environment on phosphorescent quantum yields, lifetimes, and associated radiative and non-radiative rate constants of eight organometallic complexes were studied. Single-crystal X-ray diffraction experiments and computational studies provide evidence for stabilization of metallo-cumulene resonance forms whose increased rigidities manifest in the observed photophysical changes. This effect is more pronounced for 4-ethynylpyridyl complexes over 3-ethynylpyridyl variants since the metallo-cumulene form shifts electron density to the electronegative N-atom at the para site. Furthermore, the use of σ-donating N-heterocyclic carbenes to complete the Pt-coordination environment enhanced the quantum yield of phosphorescence as high as 39% (λmax = 512 nm) with a lifetime of 21.2 μs. [ABSTRACT FROM AUTHOR]

The quantum yields of organic fluorophores used as donors in coordination-driven self-assembly often suffer from the heavy atom effect of nearby metal sites. Here, the role of intersystem crossing from a deactivating process to one that delivers emissive triplet states was reversed. A phosphorescent trans bis- N-heterocyclic carbene platinum(II) compound, Pt(dhim)2(C≡C-4-py)2 ( D1; dhim=1,3-dihexyl-2-H-imidazol-2-ylidene), was used along with other linear donors 4,4′-bipyridine ( D2) and 1,4-bis(4-pyridyl ethynyl)benzene ( D3) in self-assembly reactions with Pt(dtbpy)X2 acceptors (dtbpy=4,4′-di-tert-butyl-2,2′-bipyridine) to afford three metallacycles. Photophysical investigations revealed that, although the building blocks used to construct M1 have relatively low quantum yields ( Φ=1.2 and <1 % for D1 and 2, respectively), the metallacycle has a quantum yield of 14 %. This increase reflects a change in radiative rate constant from 3.6×104 s−1 for D1 to 2.1×105 s−1 for M1. [ABSTRACT FROM AUTHOR]

A theranostic agent combines diagnostic reporter with therapeutic activity in a single entity, an approach that seeks to increase the efficacy of cancer treatment. Herein, we describe the synthesis of a highly emissive tetraphenylethene-based metallacage using multicomponent coordination-driven self-assembly that exhibits a coordination-triggered aggregation-induced emission (AIE) enhancement. The formation of metallacage-loaded nanoparticles (MNPs) occurs when the assembly is treated with two variants of a 1,2-distearoyl-phosphatidylethanolamine (DSPE)/polyethylene glycol (PEG) conjugate, mPEG-DSPE, and biotin-PEG-DSPE. This combination endows the resultant MNPs with excellent stability and targeting ability, specifically enabling selective delivery of the metallacages to cancer cells that overexpress biotin receptors via receptor- mediated endocytosis. Although the mechanism of activity is based on existing Pt(II) anticancer drugs such as oxaliplatin, carboplatin, and cisplatin, in vitro and in vivo studies indicate that the MNPs are more active and show low systemic activity while also possessing emissive properties that allow for fluorescence-based imaging. This pioneering example of a metallacage that combines biologically active components with AIE imaging establishes supramolecular coordination complexes imbedded within nanoparticles as a promising potential theranostic platform for cancer treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • A pioneering example of incorporating [CB 11 H 12 ]- into Platinum triplet emitters. • Anionic [CB 11 H 12 ]- enforced the charge neutrality of cationic Platinum emitter. • Anionic [CB 11 H 12 ]- optimized the Platinum emitter PLQY from 54% to 97%. • OLEDs exhibited green electroluminescence with CIE coordinates of (0.28, 0.55). • OLEDs exhibited the maximum external quantum efficiency (EQE max) of 18.51%. The use of organometallic triplet emitters in OLED applications may be complicated when the luminescent complex bears a formal charge. By designing ligands containing pendant closo -monocarborane clusters [CB 11 H 11 ]−, it is possible to neutralize the otherwise cationic cores of cyclometalated Pt(II) complexes bearing bis -carbenes, resulting in significantly enhanced photophysical properties. Herein, we report four Pt(II) complexes decorated with a monoanionic closo -monocarborane by coupling the cluster to the classic cyclometallating moiety, phenylpyridine (ppy). All four complexes were fully characterized by NMR, HR-MS, UV–Vis, and cyclic voltammetry. Complexes 1b , 1c and 2a were characterized by single-crystal X-ray diffraction. Moreover, all four complexes show interesting photophysical behaviors, with complex 1a exhibiting a photoluminescent quantum yield of 97% in a 2 wt% PMMA film. This high efficiency prompted the incorporation of 1a and 1c into an OLED device using solution processing, resulting in green emission with CIE coordinates of (0.28, 0.55) for 1a and yellow emission with CIE coordinates of (0.44, 0.50) for 1c. The measured maximum external quantum efficiency (EQE max) was 18.51% for 1a , an EQE max that is among the highest for solution-processed OLED devices containing Pt(II) complexes with simple cyclometalated ppy ligands. [ABSTRACT FROM AUTHOR]

A pair of organoplatinum(II) metallacycles,M1andM2, was self-assembled by combining one of two donor molecules,cis-[Pt(dhim)2(C≡CC5H4N)2] (D1; dhim = 1,3-dihexyl-2-H-imidazole-2-yelidene) and Pt(tbbpy)(C≡CC5H4N)2(D2; tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine), with an acceptor precursor, Pt(tbbpy)(OTf)2(A1; OTf = CF3SO3−), respectively. Both donor molecules exhibit an idealized 90° angle between the coordination vectors of their ethynylpyridine moieties. When mixed withA1, coordination-driven self-assembly occurs at 50 °C (4 days in acetonitrile forM1and 18 h in CH2Cl2forM2). Both metallacycles were characterized by1H NMR, FT-IR, and FT-ICR-MS techniques that support D2A2self-assembly of molecular squares. The structure of building blockD1was determined by X-ray diffraction, confirming the expected square coordination geometry and 90° orientation of the pyridyl coordination vectors. Photophysical studies ofM1andM2reveal that the metallacycles display triplet emission bands at 466 and 469 nm, respectively, that originate from transitions localized on building blocksD1andD2. This phosphorescent behavior is assigned to3ILCT and3LLCT (πC≡C* →πC≡C; ILCT = intraligand charge transfer, LLCT = ligand-to-ligand charge transfer) transitions based on previous studies of phenyl analogs toD1andD2that indicate that the ethynyl moieties dominate in their contributions to the molecular orbitals involved in absorption and emission. [ABSTRACT FROM AUTHOR]

Materials that organize multiple functionally active sites, especially those with aggregation-induced emission (AIE) properties, are of growing interest due to their widespread applications. Despite promising early architectures, the fabrication and preparation of multiple AIEgens, such as multiple tetraphenylethylene (multi-TPE) units, in a single entity remain a big challenge due to the tedious covalent synthetic procedures often accompanying such preparations. Coordination-driven self-assembly is an alternative synthetic methodology with the potential to deliver multi-TPE architectures with light-emitting characteristics. Herein, we report the preparation of a new family of discrete multi-TPE metallacycles in which two pendant phenyl rings of the TPE units remain unused as a structural element, representing novel AIE-active metal-organic materials based on supramolecular coordination complex platforms. These metallacycles possess relatively high molar absorption coefficients but weak fluorescent emission under dilute conditions because of the ability of the untethered phenyl rings to undergo torsional motion as a non-radiative decay pathway. Upon molecular aggregation, the multi-TPE metallacycles show AIE-activity with markedly enhanced quantum yields. Moreover, on account of their AIE characteristics in the condensed state and ability to interact with electron-deficient substrates, the photophysics of these metallacycles is sensitive to the presence of nitroaromatics, motivating their use as sensors. This work represents a unification of themes including molecular self-assembly, AIE, and fluorescence sensing and establishes structure-property-application relationships of multi-TPE scaffolds. The fundamental knowledge obtained from the current research facilitates progress in the field of metal-organic materials, metal-coordination-induced emission, and fluorescent sensing. [ABSTRACT FROM AUTHOR]

Hierarchical self-assembly centeredon metallacyclic scaffoldsgreatly facilitates the construction of mechanically interlocked structures.The formation of two [3]catenanes and one [4]molecular necklace ispresented by utilizing the orthogonality of coordination-driven self-assemblyand crown ether-based cryptand/paraquat derivative complexation. Thethreaded [3]catenanes and [4]molecular necklace were fabricated byusing ten and nine total molecular components, respectively, fromfour and three unique species in solution, respectively. In all casessingle supramolecular ensembles were obtained, attesting to the highdegree of structural complexity made possible via self-assembly approaches. [ABSTRACT FROM AUTHOR]

The development of novel antitumor agents that have high efficacy in suppressing tumor growth, have low toxicity to nontumor tissues, and exhibit rapid localization in the targeted tumor sites is an ongoing avenue of research at the interface of chemistry, cancer biology, and pharmacology. Supramolecular metal-based coordination complexes (SCCs) have well-defined shapes and geometries, and upon their internalization, SCCs could affect multiple oncogenic signaling pathways in cells and tissues. We investigated the uptake, intracellular localization, and antitumor activity of two rhomboidal Pt(II)-based SCCs. Laser-scanning confocal microscopy in A549 and HeLa cells was used to determine the uptake and localization of the assemblies within cells and their effect on tumor growth was investigated in mouse s.c. tumor xenograft models. The SCCs are soluble in cell culture media within the entire range of studied concentrations (1 nM-5 μM), are nontoxic, and showed efficacy in reducing the rate of tumor growth in s.c. mouse tumor xenografts. These properties reveal the potential of Pt(II)-based SCCs for future biomedical applications as therapeutic agents. [ABSTRACT FROM AUTHOR]

Two new tetracationic hetero-bimetallacycles, compounds 4 and 5, have been constructed from an N, N′-bis(4-(pyridin-4-ylethynyl)phenyl)pyridine-2,6-dicarboxamide ligand ( 1), and cis-blocked complexes [M(dppf)(OTf)2] (dppf=1,1′-bis(diphenylphosphino)ferrocene; OTf=trifluoromethanesulfonate; M=Pd ( 2), Pt ( 3)) in CH3NO2/CH2Cl2 (1:1) solvent. Both complexes were isolated with adequate yields as triflate salts and were then characterized using 1H, 13C, and 31P NMR spectroscopy, elemental analysis, UV/Vis spectroscopy, and high-resolution electrospray mass spectrometry (HR-ESMS). The molecular structure of 4 was determined by molecular mechanics force-field calculations. The cytotoxic effect of both new complexes were analyzed against T98G (brain tumor), KB (head and neck cancer), SNU-80 (thyroid cancer), and HEK-293 non-malignant cell lines. The cytotoxicity of complexes 4 and 5 were found to be considerably more effective against cancer cells than reference drug cisplatin. Annexin-V/PI staining, caspase-3/7 activity, and the reduction in mitochondrial membrane potential justify a significant level of apoptosis in complex-treated cells. [ABSTRACT FROM AUTHOR]

Multicomponent self-assembly, wherein two unique donor precursors are combined with a single metal acceptor instead of the more common two-component assembly, can be achieved by selecting Lewis-basic sites and metal nodes that select for heteroligated coordination spheres. Platinum(II) ions show a thermodynamic preference for mixed pyridyl/carboxylate coordination environments and are thus suitable for such designs. The use of three or more unique building blocks increases the structural complexity of supramolecules. Herein, we describe the synthesis and characterization of rectangular prismatic supramolecular coordination complexes (SCCs) with two faces occupied by porphyrin molecules, motivated by the search for new multichromophore complexes with promising light-harvesting properties. These prisms are obtained from the self-assembly of a 90° Pt(II) acceptor with a meso-substituted tetrapyridylporphyrin (TPyP) and dicarboxylate ligands. The generality of this self-assembly reaction is demonstrated using five dicarboxylate ligands, two based on a rigid central phenyl ring and three alkyl-spaced variants, to form a total of five free-base and five Zn-metallated porphyrin prisms. All 10 SCCs are characterized by 31P and ¹H multinuclear NMR spectroscopy and electrospray ionization mass spectrometry, confirming the structure of each self-assembly and the stoichiometry of formation. The photophysical properties of the resulting SCCs were investigated revealing that the absorption and emission properties of the free-base and metallated porphyrin prisms preserve the spectral features associated with free TPyP. [ABSTRACT FROM AUTHOR]

Mixed matrix materials (MMMs) comprising porous fillers in polymers can exhibit superior gas separation properties, yet their practical use has been limited by poor interfacial compatibility between the two components. Herein we report a bottom-up approach to synthesize the MMMs by dispersing a metal-organic polyhedron (MOP-3) in monomer solutions before rapid photopolymerization to form interpenetrating networks (IPNs), where the porous MOP-3 nanoparticles serve as molecular dopants. Specifically, MOP-3 with particle sizes of ≈5 nm was dispersed in and infiltrated by either a macromonomer of poly(ethylene glycol) diacrylate (PEGDA) or poly(1,3 dioxolane) acrylate (PDXLA). The introduction of the MOP-3 in the polyethers decreases their glass transition temperatures and even induces the crystallization of polyPDXLA at high loadings. Increasing the MOP loading increases CO 2 permeability with a slight decrease in CO 2 /gas selectivity. For example, as the MOP content increases from 0 to 30 mass% in polyPDXLA, CO 2 permeability increases from 190 Barrer to 580 Barrer, and CO 2 /N 2 selectivity decreases from 70 to 62 at 35 °C. These IPNs-based MMMs exhibit separation properties above the Robeson's upper bounds for CO 2 /N 2 and CO 2 /H 2 separation. As the MOPs are soluble in solvents, this approach can be easily integrated into industrial membrane fabrication processes to produce MMMs-based composite membranes in large-scale. Image 1 • Metal-organic polyhedra (MOP-3) was dispersed in monomers before polymerization. • Adding MOP-3 (<5 nm) in polyethers increases chain flexibility and decreases T g. • Increasing MOP-3 loadings enhances permeability and retains CO 2 /gas selectivity. • Adding 2% MOP-3 increases gas permeability by more than 100%. • MOP-3 can be dissolved in coating solutions for large-scale membrane fabrication. [ABSTRACT FROM AUTHOR]