No abstract

Hollow polymer-based particles are useful for the encapsulation, protection, and release of active compounds. Adding a metal-organic coordination framework shell to nanocontainers is an attractive goal because it should help control their stability and permeability while yielding new properties and functions. We have discovered that polymer capsules with a Prussian blue analogue inner shell can be synthesized by emulsion-induced assembly of a metal-containing amphiphilic block ionomer. The capsules are selectively permeable and were used as nanocontainers to encapsulate and release a model compound. Further, these nanomaterials are tunable in size and organize into 2-D close-packed arrays in the solid state. Potential applications for these materials include the encapsulation and nanopatterning of pharmaceutical, biological, and catalytic compounds.

Progress in metal-organic coordination frameworks is thriving owing to the high degree of control over their properties afforded by judicial selection of their building blocks. The thermodynamic stability of the crystalline framework for these materials has made the investigation of their bulk phase convenient and successful, [1] but this stability is now the main obstacle associated with preparing nanoscale forms of these materials. Forming discrete, nanosized metal-organic coordination frameworks is a goal that may offer the opportunity to integrate new functions into their nanoscale analogues [2] and enable incorporation of these materials into new devices.Prussian blue (PB) is a metal-organic coordination framework of Fe 4 [Fe(CN) 6 ] 3 ·n H 2 O constructed from iron(II) or iron(III) vertices bridged by cyanide ligands. [3] PB and cyanometalate analogues of the general chemical formula M' a [M''(CN) x ] b can exhibit electronic delocalization and magnetic communication between the metal centers, leading to fascinating optical, electronic, and magnetic properties.[4] Nanostructured PBs, primarily nanoparticles, have been prepared by several approaches [5] and are now being explored for applications including electrochromic materials, [6] molecule-based magnets, [7] electrocatalysts [8] and photoswitches. [7b, 9] Phase-separated block copolymers offer unique reaction environments for assembling [10] and patterning [11] organic, [12] organic-inorganic hybrid, [13] and fully inorganic [14] nanomaterials. Polymers containing an ionic block are especially remarkable because of their exceptionally low critical micelle concentration and their ability to assemble into "frozen" aggregates that could potentially be used to create and pattern nanomaterials. [12b, 15] One type of ionic block copolymers, called block ionomers, [16] has been used for the preparation of quantum dots and metal nanoparticles, [17] but to our knowledge, it has never been employed in the fabrication of nanostructured metal-organic coordination frameworks.Herein we present the synthesis and characterization of a novel comb-type metal-organic block ionomer and demonstrate its assembly into soluble worm-like PB nanostructures that can form organized two-dimensional arrays upon evaporation. The nanomaterial formed from Fe III /Fe II can be further calcined in air to form mesoporous iron oxide films. Interestingly, PB nanostructures are known to exhibit superparamagnetism [18] and other types of magnetic ordering. [19] We envision that our materials could find application as soluble and patternable nanomagnetic materials and as precursors for multimetallic oxide catalysts. Our approach to construct soluble PB nanoworms is illustrated in Figure 1 a. A diblock copolymer (PS-b-PHEMA) containing 270 styrene and 30 hydroxyethylmethacrylate (HEMA) repeat units, as measured (M n ) by size exclusion chromatography (SEC), was synthesized and found to have a narrow polydispersity index (PDI = 1.04). The PHEMA block was then functionalized with brom...

[Chemical reaction: See text] Conjugated, shape-persistent macrocycles based on [3 + 3] Schiff-base condensation are of interest for supramolecular materials. In an effort to develop new discotic liquid crystals based on these compounds, a series of macrocycles with peripheral alkoxy groups of varying length have been prepared. The synthesis and mechanism of formation have been probed by isolation of oligomeric intermediates. A single-crystal X-ray diffraction study of one macrocycle revealed a nonplanar, strongly hydrogen-bonded structure. To our surprise, even with very long substituents, the macrocycles were not liquid crystalline. This has been rationalized by ab initio calculations that indicate the macrocycles are undergoing rotation of the dihydroxydiiminobenzene rings that may not allow a stable discotic liquid crystalline phase. These results provide new insight into the formation and properties of these large macrocycles and may provide guidance to developing stable liquid crystalline materials in the future.

The pure rotational spectrum of palladium monocarbonyl, PdCO, has been measured between 6000 and 24 000 MHz using a cavity pulsed jet Fourier transform microwave spectrometer. The molecules were prepared by laser ablation of Pd in the presence of CO contained in an Ar backing gas. The spectra of 15 isotopomers have been used to determine the molecular geometry from the measured rotational constants. Centrifugal distortion constants are in good agreement with those calculated from a literature harmonic force field. A nuclear quadrupole coupling constant and nuclear spin-rotation constant have been determined for 105 Pd. Nuclear shielding parameters have been evaluated from the measured spin-rotation constant. The geometry is discussed with reference to theoretical data and to other molecules containing an M-CO bond.