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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.

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]

An emerging strategy for the fabrication of advanced supramolecular materials is the use of hierarchical self-assembly techniques wherein multiple orthogonal interactions between molecular precursors can produce new species with attractive properties. Herein, we unify the spontaneous formation of metal-ligand bonds with the host/guest chemistry of crown ethers to deliver a 3D supramolecular polymer network (SPN). Specifically, we have prepared a highly directional dipyridyl donor decorated with a benzo-21-crown-7 moiety that undergoes coordination-driven self-assembly with a complementary organoplatinum acceptor to furnish hexagonal metallacycles. These hexagons subsequently polymerize into a supramolecular network upon the addition of a bisammonium salt due to the formation of [2]pseudorotaxane linkages between the crown ether and ammonium moieties. At high concentrations, the resulting 3D SPN becomes a gel comprising many cross-linked metallohexagons. Notably, thermo- and cation-induced gel-sol transitions are found to be completely reversible, reflecting the dynamic and tunable nature of such supramolecular materials. As such, these results demonstrate the structural complexity that can be obtained when carefully controlling multiple interactions in a hierarchical fashion, in this case coordination and host/guest chemistry, and the interesting dynamic properties associated with the materials thus obtained. [ABSTRACT FROM AUTHOR]

Metal ions and metal complexes with organic molecules are ubiquitous in nature. Bulk metal ions of Na, K, Mg, and Ca constitute as much as 1% of human body weight. The remaining trace ions, most commonly of Fe, Ni, Cu, Mn, Zn, Co, Mo, and V, make up ∼0.01% by weight, but their importance in biological processes cannot be overstated. [ABSTRACT FROM AUTHOR]

The photophysical properties of bis(phosphine) Pt(II) complexes constructed from 2,6-bis(pyrid-3-ylethynyl) aniline and 2,6-bis(pyrid-4-ylethynyl) aniline vary significantly, even though the complexes differ only in the position of the coordinating nitrogen. By capping the ligands with an aryl bis(phosphine) Pt(II) metal acceptor, the photophysical properties of the two isomeric systems were directly compared, revealing that the low-energy absorption and emission bands of the two systems were separated by 30 nm (1804 cm-1) and 39 nm (1692 cm-1), respectively. From the analysis of time-dependent density functional (TD-DFT) calculations and excited-state lifetime measurements, it was determined that the nature of the Pt-N bond in the HOMO and the sums of the radiative (krad) and nonradiative (knr) rate constants were significantly different in the two systems. As the dominant nonradiative decay pathway in aniline systems is relaxation from the triplet state through intersystem crossing (ISC), the difference in knr can be ascribed to changes in ISC between isomers of the bis(phosphine) Pt(II)-capped 2,6-bis(pyrid-3-ylethynyl) aniline system. It was also determined that the photophysical properties of these capped systems can be altered by functionalizing the aryl capping ligand on the bis(phosphine) Pt(II) metal center, which perturbs the molecular orbitals involved in the observed optical transitions. In addition, an isoelectronic bis(phosphine) Pd(II)-capped system was prepared for comparison with the bis(phosphine) Pt(II) suite of complexes. The Pd(II) system showed significant changes in its low-energy absorption band, but preserved the characteristic emissive properties of its Pt(II) analogue with an even higher quantum yield. [ABSTRACT FROM AUTHOR]

The article discusses the importance of metal-organic structural frameworks and self-assembled supramolecular coordination chemical complexes in co-ordination chemistry. It mentions that the structural frameworks are beneficial in study of multicomponent chemical assembly and post self assembly chemical modifications. It mentions that the co-ordination chemistry approach is useful in chemical study involving metal ligands.

A series of endohedral and exohedral amine-functionalized ligands were synthesized and used in the construction of supramolecular D2h rhomboids and a D6h hexagon. These supramolecular polygons were obtained via self-assembly of 1200 dipyridyl donors with 180° or 120° diplatinum precursors when combined in 1:1 ratios. Steady-state absorption and emission spectra were collected for each ligand and metallacycle. Density functional theory (DFT) and time-dependent DFT calculations were employed to probe the nature of the observed optical transitions for the rhomboids. The emissive properties of these bis(phosphine) organoplatinum metallacycles arise from ligand-centered transitions involving π-type molecular orbitals with modest contributions from metal-based atomic orbitals. The D211 rhomboid self-assembled from 2,6-bis(4-pyridylethynyl)aniljne and a 60° organoplatinum(ll) acceptor has a low-energy excited state in the visible region and emits above 500 nm, properties which greatly differ from those of the parent 2,6-bis(4-pyridylethynyl)aniline ligand. [ABSTRACT FROM AUTHOR]

The heterobimetallic complexes, PtRh(tfepma)2(CNtBu)X3 (X = Cl, Br), are assembled by the treatment of Pt(cod)X2 (cod =1,5-cyclooctadiene) with {Rh(cod)X}2, in the presence of tert-butylisonitrile (CNtBu) and tfepma (tfepma = bis(trifluoroethoxyl)phosphinomethylamine). The neutral complexes contain Pt-Rh single bonds with metal-metal separations of 2.6360(3) and 2.6503(7) Å between the square planar Pt and octahedral Rh centers for the Cl and Br complexes, respectively. Oxidation of the XPtIRhIIX2 cores with suitable halide sources (PhICl2 or Br2) furnishes PtRh(tfepma)2(CNtBu)X5, which preserves a Pt-Rh bond. For the chloride system, the initial oxidation product orients the platinum-bound chlorides in a meridional geometry, which slowly transforms to a facial arrangement in pentane solution as verified by X-ray crystal analysis. Irradiation of the mer- or fac-Cl3PtIIIRhIICl2 isomers with visible light in the presence of olefin promotes the photoelimination of halogen and regeneration of the reduced ClPtIRhIICl2 core. In addition to exhibiting photochemistry similar to that of the chloride system, the oxidized bromide cores undergo thermal reduction chemistry in the presence of olefin with zeroth-order olefin dependence. Owing to an extremely high photoreaction quantum yield for the fac-ClPtIRhIICl2 isomer, details of the X2 photoelimination have been captured by transient absorption spectroscopy. We now report the first direct observation of the photointermediate that precedes halogen reductive elimination. The intermediate is generated promptly upon excitation (<8 ns), and halogen is eliminated from it with a rate constant of 3.6 × 104 s-1. As M-X photoactivation and elimination is the critical step in HX splitting, these results establish a new guidepost for the design of HX splitting cycles for solar energy storage. [ABSTRACT FROM AUTHOR]

The syntheses and reaction chemistry of two electron mixed-valence diphosphazane-bridged dirhodium and diiridium complexes M20,II(tfepma)2(CNtBu)2Cl2 [M = Rh (1), Ir (2); tfepma = MeN[P(OCH2CF3)2]2, CNtBu = tert-butyl isocyanide] are described. 1 and 2 undergo addition and two-electron oxidation and reduction chemistries. In the presence of CNtBu, the addition product with the stoichiometry M20,II(tfepma)2(CNtBu)3Cl2 [M = Rh (3), Ir (3)] is generated; in the presence of 1 equiv of CNtBu and 2 equiv of bis(pentamethyl-cyclopentadienyl)cobalt(II), 1 and 2 are reduced to furnish M20,0(tfepma)2(CNtBu)3 [M = Rh (5), Ir (6)], which feature both four- and five-coordinate M0 centers. Complexes 1, 2, 5, and 6 all possess coordinatively unsaturated square planar M0 centers that are reactive: (1) 2 reacts with PhICl2 to produce Ir2II,II(tfepma)2(CNtBu)2Cl4 (7); (2) protonation of 2 with HX yields Ir2II,II(tfepma)2(CNtBu)2Cl2HX [X = Cl- (8), OTs- (9)]; (3) protonation of 5 with HOTs produces [Rh2I,I(tfepma)2(CNtBu)3(μ-H)](OTs); and (4) the reversible hydrogenation of 2 proceeds smoothly, furnishing the cis-dihydride complex Ir2II,II(tfepma)2(CNtBu)2(H)2Cl2 (11). Substitution of tfepma in 2 with bis(diphenylphsophino)methane (dppm) yields the orthometalated complex Ir2II,II(dppm)(PPh(o-C6H4)CH2PPh2)(CNtBu)2Cl2H (12). The X-ray crystal structures of 11 compounds are presented and discussed, and spectroscopic characterization by multinuclear and variable temperature NMR provides details about solution structures and in some cases the formation of isomeric products. The electronic spectra of the new complexes are also described briefly, with absorption and emission features derived from the bimetallic core. [ABSTRACT FROM AUTHOR]

The article discusses a study on solar energy supply for the legacy and nonlegacy worlds for an estimated 9.4 billion people by the year 2050. It states that delivering an additional 16 terawatts (TW) is difficult because biomass, nuclear energy, wind energy and other energy sources are insufficient for the increasing global energy consumption. The study noted that sunlight is the preeminent carbon-neutral energy source and that delivering personalized solar energy provides a solution for the world's future energy supply.

The key intermediate in dinitrogen cleavage by Mo(N[t-Bu]Ar)3, 1 (Ar = 3,5-C6H3Me2), has been characterized by a pair of single crystal X-ray structures. For the first time, the X-ray crystal structure of (μ-N2)[Mo(N[t-Bu]Ar)3]2, 2, and the product of homolytic fragmentation of the NN bond, NMo(N[t-Bu]Ar)3, are reported. The structural features of 2 are compared with previously reported EXAFS data. Moreover, contrasts are drawn between theoretical predictions concerning the structural and magnetic properties of 2 and those reported herein. In particular, it is shown that 2 exists as a triplet (S = 1) at 20 °C. Further insight into the bonding across the MoNNMo core of the molecule is obtained by the synthesis and structural characterization of the one- and two-electron oxidized congeners, (μ-N2)[Mo(N[t-Bu]Ar)3]2[B(ArF)4], 2[B(ArF)4] (ArF = 3,5-C6H3(CF3)2) and (μ-N2)[Mo(N[t-Bu]Ar)3]2[B(ArF)4]2, 2[B(ArF)4]2, respectively. Bonding in these three molecules is discussed in view of X-ray crystallography, Raman spectroscopy, electronic absorption spectroscopy, and density functional theory. Combining X-ray crystallography data with Raman spectroscopy studies allows the NN bond polarization energy and N-N internuclear distance to be correlated in three states of charge across the MoNNMo core. For 2[B(ArF)4], bonding is symmetric about the μ-N2 ligand and the NN polarization is Raman active; therefore, 2[B(ArF)4] meets the criteria of a Robin-Day class Ill mixed-valent compound. The redox couples that interrelate 2, 2+, and 22+ are studied by cyclic voltammetry and spectroelectrochemistry. Insights into the electronic structure of 2 led to the discovery of a photochemical reaction that forms NMo(N[t-Bu]Ar)3 and Mo(N[t-Bu]Ar)3 through competing NN bond cleavage and N2 extrusion reaction pathways. The primary quantum yield was determined to be Φp = 0.05, and transient absorption experiments show that the photochemical reaction is complete in less than 10 ns. [ABSTRACT FROM AUTHOR]

The article offers information on a research conducted in order to determine chlorine photoelimination. The research has revealed that photolysis of a Pt2 with ultraviolet (UV) or visible light in the solid state yields chlorine. The research has also revealed energy storage reactivity in the absence of a halogen trap.

The article describes the preparation and characterization of the first PtAu compound. According to the authors, the d7-d9 complex exhibits a facile two-electron chemically assisted halogen photoelimination that is promoted by visible light. They add the electronic absorption spectrum of platinum compound features a dominant band centered at 338 nm.

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]

We describe the efficient preparation of rhomboidal metallacycles that self-assemble upon mixing a donor decorated with 2-ureido-4-pyrimidinone (UPy) with acceptors containing pendant [G1]-[G3] dendrons. The formed rhomboids subsequently polymerize into dendronized organoplatinum(II) metallacyclic polymers through H-bonding UPy interfaces, which possess the structural features of conventional dendronized polymers as well as the dynamic reversibility of supramolecular polymers. Preservation of both properties in a single material is achieved by exploiting hierarchical self-assembly, namely the unification of coordination-driven self-assembly with H-bonding, which provides facile routes to dendronized metallacycles and subsequent high ordering. The supramolecular polymerization defined here represents a novel method to deliver architecturally complex and ordered polymeric materials with adaptive properties. [ABSTRACT FROM AUTHOR]

Metallacyclic cores provide a scaffold upon which pendant functionalities can be organized to direct the formation of dimensionally controllable nanostructures. Because of the modularity of coordination-driven self-assembly, the properties of a given supramolecular core can be readily tuned, which has a significant effect on the resulting nanostructured material. Herein we report the efficient preparation of two amphiphilic rhomboids that can subsequently order into 0D micelles, 1D nanofibers, or 2D nanoribbons. This structural diversity is enforced by three parameters: the nature of the hydrophilic moieties decorating the parent rhomboids, the concentration of precursors during self-assembly, and the reaction duration. These nanoscopic constructs further interact to generate metallohydrogels at high concentrations, driven by intermolecular hydrophobic and π-π interactions, demonstrating the utility of coordinationdriven self-assembly as a first-order structural element for the hierarchical design of functional soft materials. [ABSTRACT FROM AUTHOR]

Supramolecular coordination complexes (SCCs) have been proposed for applications necessitating photon emitting properties; however, two critical characteristics, facile tunability and high emission quantum yields, have yet to be demonstrated on SCC platforms. Herein, a series of functionalized D2h [D2A2] rhomboids (D = 2,6-bis(4-ethynylpyridine)aniline-based ligands; A = 2,9-bis[trans-Pt(PEt3)2NO3]phenanthrene) is described with emission wavelengths spanning the visible region (Λmax = 476-581 nm). Tuning was achieved by simple functional group modifications para to the aniline amine on the donor building block. Steady-state absorption and emission profiles were obtained for each system and are discussed. When the Hammett spara constants for the functional groups σpara to the aniline amine were plotted versus the wavenumber (cm-1) for the Λmax of the emission profile, a linear relationship was observed. By utilizing this relationship, the emission wavelength of a given rhomboid can be predetermined on the basis of the Hammett constant of the functionality employed on the donor precursor. This range of visible light emission for a suite of simple rhomboids along with the predictive nature of the wavelength of emission is unprecedented for these types of systems. [ABSTRACT FROM AUTHOR]

In this work, spectroscopic techniques and quantum chemistry calculations were used to investigate the photophysical properties of various multinuclear platinum complexes with different conformational geometries. This suite of complexes includes a Pt–pyridyl square, a Pt–carboxylate triangle, and a mixed Pt–pyridyl–carboxylate rectangle, as well as two mononuclear Pt model complexes. Studying the individual molecular precursors in the context of larger assemblies is important to provide a complete understanding of the factors governing the observed photophysical properties of a given system. The absorption and emission bands of the parent linear dipyridyl donor (ligand 1) are largely preserved in the [4 + 4] square and the multicomponent [4 + 2 + 2] rectangle (3 and 4, respectively), with significant red shifts. The [3 + 3] Pt–carboxylate triangle containing p-phthalic acid is nonemissive. Phosphorescence and nanosecond transient spectroscopy on 3 and 4 reveal that the introduction of platinum atoms enhances spin–orbital coupling, thereby increasing the rate of intersystem crossing. This phenomenon is consistent with the low fluorescence quantum yields and short fluorescence lifetimes of 3 and 4. Moreover, the electronic structures for the ground state and low-lying excited states of these compounds were studied using quantum chemistry calculations. The fluorescent states of the platinum complexes are local excited states of ligand-centered π-π* transition features, whereas the nonfluorescent states are intramolecular charge-transfer states. These low-lying intramolecular charge-transfer states are responsible for the nonemissive nature of small molecules 1 and 2 and triangle 5. As the interactions between these components determine the properties of their corresponding assemblies, we establish novel excited-state decay mechanisms which dictate the observed spectra. [ABSTRACT FROM AUTHOR]

We describe the formation of a suite of [3]catenanes via multicomponent coordination-driven self-assembly and host–guest complexation of a rectangular scaffold comprising a 90° Pt-based acceptor building block with a pseudorotaxane bis(pyridinium)ethane/dibenzo-24-crown-8 linear dipyridyl ligand and three dicarboxylate donors. The doubly threaded [3]catenanes are formed from a total of 10 molecular components from four unique species. Furthermore, the dynamic catenation process is reversible and can be switched off and on in a controllable manner by successive addition of KPF6 and 18-crown-6, as monitored by 1H and 31P NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The 90° and 60° bimetallic platinum complexeswith specialstructures are widely used in coordination-driven self-assembled metallosupramoleculararchitectures, and these complexes are the key components of triangular,rectangular, and polygonal metallacycle and metallocage supramolecules.Therefore, spectroscopic techniques and quantum chemistry calculationswere employed in this article to investigate the photophysical propertiesof these bimetallic platinum complexes. Compared with spectra forthe ligands, the absorption spectra of these Pt complexes are red-shifted,and the fluorescence spectra become wider and are also red-shifted.Moreover, the reasons for the low fluorescence quantum yields andshort fluorescence lifetimes of these compounds were investigatedusing quantum chemistry calculations. We demonstrate that the fluorescentstates of the bimetallic platinum complexes can be considered as localexcited states, and that they possess a ligand-centered π–π*transition feature. Meanwhile, the platinum metals act as perturbationfor these transitions, whereas the nonfluorescent states are classifiedas intramolecular charge-transfer states. Furthermore, a new fluorescencemodulation mechanism is developed to explain the different emissionprocesses of these complexes with different ligands. [ABSTRACT FROM AUTHOR]

A novel, interlocked, self-assembled (M2L2)2 molecular architecture was constructed from an arene-Ru acceptor and a 1,4-di(pyridin-4-yl)buta-1,3-diyne donor. Two M2L2 units, with cavities of ∼7.21 Å, spontaneously interlock, with one unit encapsulating a twin in a non-catenane fashion. The dimeric host-guest complex thus formed is unique among two-dimensional self-assemblies and is stabilized by π-π interactions between the M2L2 units. [ABSTRACT FROM AUTHOR]

A new approach for the construction of functionalized metallosupramolecular tetragonal prisms via multicomponent, coordination-driven, template-free self-assembly is described. The combination of tetra-(4-pyridylphenyl)ethylene, a 90° Pt(II) acceptor, and ditopic bipyridine or carboxylate ligands functionalized with hydroxyl or amine groups, hydrophobic alkyl chains, or electrochemically active ferrocene, yields a suite of seven self-assembled tetragonal prisms under mild conditions. These three-dimensional metallosupramolecules were characterized by multinuclear NMR (31P and ¹H) and mass spectrometry. Their shapes and sizes were established using Merck Molecular Force Field (MMFF) simulations. In addition, their approximate sizes were further supported by pulsed-field-gradient spin-echo (PGSE) NMR experiments. [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]

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 formation of catenated systems can be simplified greatly if one or more rings are generated via self-assembly. Herein we exploit the orthogonality of coordination-driven self-assembly and crown-ether host-guest complexation to obtain a [4] molecular necklace and a [7]molecular necklace based on a well-developed recognition motif of 1,2-bis(pyridinium)ethane/ dibenzo[24]crown-8. By adapting the bis(pyridinium) motif into the backbone of a donor building block, the resulting semirigid dipyridyl species can serve both as a structural element in the formation of metallacycles and as a site for subsequent host-guest chemistry. The pseudo-linear nature of the donor precursor lends itself to the formation of triangular and hexagonal central metallacycles based on the complementary acceptor unit used. This exemplary system organizes up to 18 molecules from three unique species in solution to afford a single supramolecular ensemble. [ABSTRACT FROM AUTHOR]

We report a joint computational and experimental study on the concentration-dependent self-assembly of a flat C3-symmetric molecule at surfaces. As a model system we have chosen a rigid molecular module, 1,3,5-tris(pyridine-4-ylethynyl)benzene, which can undergo self-association via hydrogen bonding (H-bonding) to form ordered 2D nanostructures. In particular, the lattice Monte Carlo method, combined with density functional calculations, was employed to explore the spontaneous supramolecular organization of this tripod-shaped molecule under surface confinement. We analyzed the stability of different weak H-bonded patterns and the influence of the concentration of the starting molecule on the 2D supramolecular packing. We found that ordered, densely packed monolayers and 2D porous networks are obtained at high and low concentrations, respectively. A concentration-dependent scanning tunneling microscopy investigation of the molecular self-assembly at a graphite-solution interface revealed supramolecular motifs, which are in perfect agreement with those obtained by simulations. Therefore, our computational approach represents a step forward toward the deterministic prediction of molecular self-assembly at surfaces and interfaces. [ABSTRACT FROM AUTHOR]

A series of supramolecular rectangles, including two mixed-metal Ru/Pt complexes, have been formed by the coordination-driven self-assembly of a range of arene–Ru "molecular clip" acceptors (1a–1d) with rigid dipyridyl-based ligands (2a–2d) over the course of 10 h in solution. The isolated products were characterized by multinuclear NMR (1H and 13C or 31P), HR-ESI-MS, and an X-ray diffraction study to support the ascribed two-component rectangular structures. The rectangles were further characterized by UV–vis and fluorescence studies. The redox behaviors of rectangles 3ca and 3da were also determined using cyclic voltammetry. Additionally, the antitumor activities of the suite of rectangles were determined against various human cancer cell lines, and significant activity was shown by complexes 3ca, 3da, 3cb, 3cc, and 3cd, with IC50 values as low as 2.65 μM. [ABSTRACT FROM AUTHOR]

The multicomponent coordination-driven self-assembly of hexakis[4-(4-pyridyl)phenyl]benzene, cis-(PEt3)2PtII(OTf)2, and amine- or maleimide-functionalized isophthalate forms discrete hexagonal prisms as single reaction products. The amino or maleimide groups decorating the isophthalate pillars of the prisms provide reactive sites for post-self-asssembly modifications. In this communication, we demonstrate that the hexagonal prisms can be functionalized without disrupting the prismatic cores, enabling the incorporation of new functionalities under mild conditions. [ABSTRACT FROM AUTHOR]

A novel approach toward the construction of multicomponent two-dimensional (2-D) and three-dimensional (3-D) metallosupramolecules is reported. Simply by mixing carboxylate and pyridyl ligands with cis-Pt(PEt3)2(OTf)2 in a proper ratio, coordination-driven self-assembly occurs, allowing for the selective generation of discrete multicomponent structures via charge separation on the metal centers. Using this method, a variety of 2-D rectangles and 3-D prisms were prepared under mild conditions. Moreover, multicomponent self-assembly can also be achieved by supramolecule-to-supramolecule transformations. The products were characterized by 31P and ¹H multinuclear NMR spectroscopy, electrospray ionization mass spectrometry, and pulsed-field-gradient spin echo NMR techniques together with computational simulations. [ABSTRACT FROM AUTHOR]