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We demonstrate here how nitrate salts of bivalent copper, nickel, cobalt, and manganese, along with an achiral organic ligand, assemble into various structures such as symmetrical double‐decker flowers, smooth elongated hexagonal bipyramids, and hexagonal prisms. Large morphological changes occur in these structures because of different metal cations, although they maintain isomorphous hexagonal crystallographic structures. Metal cations with stronger coordination to ligands (Cu and Ni) tend to form uniform crystals with unusual shapes, whereas weaker coordinating metal cations (Mn and Co) produce crystals with more regular hexagonal morphologies. The unusual flower‐like crystals formed with copper nitrate have two pairs of six symmetrical petals with hexagonal convex centers. The texture of the petals indicates dendritic growth. Two different types of morphologies were formed by using different copper nitrate‐to‐ligand ratios. An excess of the metal salt results in uniform and hexagonal crystals having a narrow size distribution, whereas the use of an excess of ligand results in double‐decker morphologies. Mechanistically, an intermediate structure was observed with slightly concave facets and a domed center. Such structures most likely play a key role in the formation of double‐decker crystals that can be formed by fusion processes. The coordination chemistry results in isostructural chiral frameworks consisting of two types of continuous helical channels. Four pyridine units from four separate ligands are coordinated to the metal center in a plane having a chiral (propeller‐type) arrangement. The individual double‐decker flower crystals are homochiral and a batch consists of crystals having both handedness. [ABSTRACT FROM AUTHOR]

Formation of highly interpenetrated frameworks is demonstrated. An interesting observation is the presence of very large adamantane‐shaped cages in a single network, making these crystals new entries in the collection of diamondoid‐type metal–organic frameworks (MOFs). The frameworks were constructed by assembling tetrahedral pyridine ligands and copper dichloride. Currently, the networks' degree of interpenetration is among the highest reported and increases when the size of the ligand is increased. Highly interpenetrated frameworks typically have low surface contact areas. In contrast, in our systems, the voids take up to 63 % of the unit cell volume. The MOFs have chiral features but are formed from achiral components. The chirality is manifested by the coordination chemistry around the metal center, the structure of the helicoidal channels, and the motifs of the individual networks. Channels of both handednesses are present within the unit cells. This phenomenon shapes the walls of the channels, which are composed of 10, 16, or 32 chains correlated with the degree of interpenetration 10‐, 16‐, and 32‐fold, respectively. By changing the distance between the center of the ligand and the coordination moieties, we succeeded in tuning the diameter of the channels. Relatively large channels were formed, having diameters up to 31.0 Å×14.8 Å. [ABSTRACT FROM AUTHOR]

Since the first description of coordination complexes, many typesof metal–ligand interactions have creatively been used in thechemical sciences. The rich coordination chemistry of pyridine-typeligands has contributed significantly to the incorporation of diversemetal ions into functional materials. Here we discuss molecular assemblies(MAs) formed with a variety of pyridine-type compounds and a metalcontaining cross-linker (e.g., PdCl2(PhCN2)).These MAs are formed using Layer-by-Layer (LbL) deposition from solutionthat allows for precise fitting of the assembly properties throughmolecular programming. The position of each component can be controlledby altering the assembly sequence, while the degree of intermolecularinteractions can be varied by the level of π-conjugation andthe availability of metal coordination sites. By setting the structuralparameters (e.g., bond angles, number of coordination sites, geometry)of the ligand, control over MA structure was achieved, resulting insurface-confined metal–organic networks and oligomers. UnlikeMAs that are constructed with organic ligands, MAs with polypyridylcomplexes of ruthenium, osmium, and cobalt are active participantsin their own formation and amplify the growth of the incoming molecularlayer. Such a self-propagating behavior for molecular systems is rare,and the mechanism of their formation will be discussed. These exponentiallygrowing MAs are capable of storing metal salts that can be used duringthe buildup of additional molecular layers. Various parameters influencingthe film growth mechanism will be presented, including (i) the numberof binding sites and geometry of the organic ligands, (ii) the metaland the structure of the polypyridyl complexes, (iii) the influenceof the metal cross-linker (e.g., second or third row transition metals),and (iv) the deposition conditions. By systematic variation of theseparameters, switching between linear and exponential growth couldbe demonstrated for MAs containing structurally well-defined polypyridylcomplexes. The porosity of the MAs has been estimated by using electrochemicallyactive probes. Incorporating multiple polypyridyl complexes of osmiumand ruthenium into a single assembly give rise to composite materialsthat exhibit interesting electrochemical and electrochromic properties.These functional composites are especially attractive as they exhibitproperties that neither of each metal complex possesses individually.Some of our MAs have very high coloration efficiencies, redox stability,fast responsive times and operate at voltages < 1.5 V. Moreover,their electrochemical properties are dependent on the deposition sequenceof the polypyridyl complexes, resulting in MAs that possesses distinctiveelectron transfer pathways. Finally, some of these MAs are describedin terms of their practical applications in electrochromic materials,storage-release chemistry, solar cells, and electron transport properties. [ABSTRACT FROM AUTHOR]

We report here a new methodology for the formation of freestanding nanotubes composed of individual gold nanoparticles (NPs) cross-linked by coordination complexes or porphyrin molecules using WS2 nanotubes (INT-WS2) as a template. Our method consists of three steps: (i) coverage of these robust inorganic materials with monodispersed and dense monolayers of gold NPs, (ii) formation of a molecular AuNP network by exposing these decorated tubes to solutions containing a ruthenium polypyridyl complex or meso-tetra(4-pyridyl)porphyrin, and (iii) removal of the INT-WS2 template with a hydrogen peroxide solution. Nanoindentation of the template-free AuNP tubes with atomic force microscopy indicates a radial elastic modulus of 4 GPa. The template-free molecular AuNP tubes are characterized using scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, and micro-Raman spectroscopy. The methodology provides a convenient and scalable strategy for the realization of molecular AuNP tubes with a defined length and diameter, depending on the dimensions of the template. [ABSTRACT FROM AUTHOR]

Review: 50 refs. [ABSTRACT FROM AUTHOR]

This combined experimental and computational study demonstrates how a metal center can drastically influence the reactivity of a coordinated ligand. We found that the consecutive formation of zerovalent bimetallic complexes proceeds by fast η²-C C coordination of only one Pd(PEt3)2 moiety, which then significantly slows down the subsequent reaction. Electronic effects induced by complexation of the first metal center have a major effect on the subsequent formation of the bimetallic complexes. These effects are reduced by partial fluorination of the bis(vinylpyridine)-arene ligand. The monometallic complexes display migration of the Pd(PEt3)2 moiety between the two olefinic bonds of the corresponding ligand, as indicated by various solution NMR experiments, including variable-temperature NMR spectroscopy, 2D ¹H-¹H exchange spectroscopy, and spin saturation transfer. Density functional theory studies were performed at the SMD(toluene)-PBE0+d(v3)/B2//B97D/B1 level of theory. [ABSTRACT FROM AUTHOR]

Surface-confined double-helical polymers are generated by dynamic covalent assembly with preservation of chirality, metal coordination environment, and oxidation state of the precursor complexes. This one-step procedure involves both in solution and solution-to-surface assembly and resulted in chiral interfaces where pairs of ligands are wrapped around arrays of metal ions. In-plane XRD experiments revealed the formation of a highly ordered structure along the substrate surface. The chirality of the surfaces is expressed by the selective recognition of 3,4-dihydroxyphenylalanine (DOPA). The CD measurements show a response of the Δ-polymer-modified quartz substrates toward d-DOPA, whereas no change was observed after treatment with L-DOPA. These coordination-based interfaces assembled on metal-oxide substrates in combination with a redox-probe, [Os(bpy)3](PF6)2, in solution can resemble the behavior of a rectifier. [ABSTRACT FROM AUTHOR]