1,721,068 research outputs found
One-pot Synthesis of a Truncated Cone-shaped Porphyrin Macrocycle and Its Self-assembly into Permanent Porous Material
No full text© 2021 Wiley-VCH GmbHHere, we report the synthesis of a truncated cone-shaped triangular porphyrinic macrocycle, P3L3, via a single step imine condensation of a cis-diaminophenylporphyrin and a bent dialdehyde-based linker as building units. X-ray diffraction analysis reveals that the truncated cone-shaped P3L3 molecules are stacked on top of each other by π⋯π and CH⋯π interactions, to form 1.7 nm wide hollow columns in the solid state. The formation of the triangular macrocycle is corroborated by quantum chemical calculations. The permanent porosity of the P3L3 crystals is demonstrated by several gas sorption experiments and powder X-ray diffraction analysis.11Nsciescopu
Fuel-Driven Transient Crystallization of a Cucurbit[8]uril-Based Host-Guest Complex
No full text© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimTransient self-assembling systems often suffer from accumulation of chemical wastes that interfere with the formation of pristine self-assembled products in subsequent cycles. Herein, we report the transient crystallization of a cucurbit[8]uril-based host-guest complex, preventing the accumulation of chemical wastes. Base-catalyzed thermal decarboxylation of trichloroacetic acid that chemically fuels the crystallization process dissolves the crystals, and produces volatile chemical wastes that are spontaneously removed from the solution. With such self-clearance process, no significant damping in the formation of the crystals was observed. The morphology and structural integrity of the crystals was also maintained in subsequent cycles. The concept may be further extended to obtain other temporally functional materials, quasicrystals, etc., based on stimuli-responsive guest molecules11sciescopu
Programmable Synthesis of Silver Wheels
No full textThe synthesis of sandwich-shaped multinuclear silver complexes with planar penta- and tetranuclear wheel-shaped silver units and a central anion, [Ag-n(2-HPB)(2)(A(-))](OTf-)(n-1), nAg(A), n = 4 or 5 and A(-) = OH- or F- or Cl-, is reported, along with complete spectroscopic and structural characterization. An NMR mechanistic study reveals that silver complexes were formed in the following order: 2Ag -> 3Ag(H2O) -> 5Ag(OH) -> 4Ag(OH). The central hydroxides in 4Ag(OH) and 5Ag(OH) exhibit exotic physical properties due to the confined environment inside the complex. The size of these silver wheels can be tuned by changing the central anion or extracting/adding one silver atom. This study provides the facile way to synthesize discrete wheel-shaped multinuclear silver complexes and provides valuable insights into the dynamics of the self-assembly process.11Nsciescopu
Transient Self-assembly Processes Operated by Gaseous Fuels under Out-of-Equilibrium Conditions
No full text© 2020 Wiley-VCH GmbH. Herein we report transient out-of-equilibrium self-assembly of molecules operated by gaseous fuel mixtures. The combination of an active gaseous chemical fuel and an inert gas or compressed air, which assists the degassing of the gaseous fuel from the solution, drives the transient self-assembly process. The gaseous nature of the fuel as well as the exhaust helps in their easy removal and thereby prevents their accumulation within the system and helps in maintaining the efficiency of the transient self-assembly process. The strategy is executed with a rather simple experimental set up and operates at ambient temperatures. Our approach may find use in the development of smart materials suitable for applications such as temporally active gas sensing and sequestration11sciescopu
Dramatically Enhanced Reactivity of Fullerenes and Tetrazine towards the Inverse-Electron-Demand Diels-Alder Reaction inside a Porous Porphyrinic Cage
No full textInverse-electron-demand Diels-Alder reaction (IEDDA) between fullerenes and 1,2,4,5-tetrazine generally requires harsh conditions and long reaction times due to their strong electron-accepting nature. Herein, we report a dramatic enhancement in the reactivity of the fullerenes (C-60/C-70)-tetrazine reaction inside a porous Zn-porphyrinic cage (Zn-PB) under sustainable conditions by installing a tetrazine-based axle (LA) via metal-ligand coordination bond, which modulates the cavity size to facilitate the encapsulation of fullerenes. Upon encapsulation, the close proximity of fullerenes and the tetrazine group of LA dramatically increase their reactivity towards the IEDDA reaction to form fullerene-tetrazine adducts. Furthermore, the C-60-tetrazine adduct is rearranged upon hydration to a bent-shaped C-60-pyrazoline adduct that can be released from the Zn-PB cavity in the presence of excess LA, thus catalyzing the formation of C-60-pyrazoline adduct inside Zn-PB without product inhibition.11Nsciescopu
Hollowing out MOFs: hierarchical micro- and mesoporous MOFs with tailorable porosity via selective acid etching
Full text linkWe report a new strategy for the synthesis of robust hierarchical micro- and mesoporous MOFs from water stable MOFs via a selective acid etching process. The process is controlled by the size-selective diffusion of acid molecules through the MOF windows. This method enables the fine-tuning of the porosity of hierarchical MOFs, allowing for the generation of well-defined mesopores with high mesopore volume. Because of the size-selective diffusion of acid molecules, the inherent crystallinity and external morphology of the resulting MOFs are well-maintained after acid treatment. This novel strategy may provide an alternative route towards the synthesis of diverse hierarchical MOFs.1115Ysciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Point-of-Use Detection of Amphetamine-Type Stimulants with Host-Molecule-Functionalized Organic Transistors
No full textIn recent years, there has been a rapid increase in the abuse of amphetaminetype
stimulants (ATS). One way to tackle this problem is to develop an easy,
sensitive, rapid, and cheap ATS detection platform. Here, a strategy that synergistically
combines the selectivity of supramolecular chemistry and the sensitivity
of organic field-effect transistors is used as the basis of an ATS sensor.
Cucurbit[7]uril derivatives that can selectively detect ATS have been synthesized
and used as a functional material. The fabricated amperometric sensors
exhibited unprecedented sensitivity toward ATS, with a detection limit of nanomolar
concentrations in urine and picomolar concentrations in water or a physiologic
buffer. The feasibility of this strategy was further demonstrated through
the preparation of flexible and wearable devices with a wireless sensing platform.
This sensing system offers rapid and sensitive detection of trace amounts
of ATS in urine and other samples at the point of use.2017 (c) 2017 Elsevier Inc.11Nscopu
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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