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Abstract Addition of the bipyridyl‐embedded cycloparaphenylene nanohoop bipy[9]CPP to [Fe{H2B(pyz)2}] (pyz=pyrazolyl) produces the distorted octahedral complex [Fe(bipy[9]CPP){H2B(pyz)2}2] (1). The molecular structure of1shows that the nanohoop ligand contains a non‐planar bipy unit. Magnetic susceptibility measurements indicate spin‐crossover (SCO) behaviour with aT1/2of 130 K, lower than that of 160 K observed with the related compound [Fe(bipy){H2B(pyz)2}2] (2), which contains a conventional bipy ligand. A computational study of1and2reveals that the curvature of the nanohoop leads to the different SCO properties, suggesting that the SCO behaviour of iron(II) can be tuned by varying the size and diameter of the nanohoop.
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A High‐Yielding Active Template Click Reaction (AT−CuAAC) for the Synthesis of Mechanically Interlocked Nanohoops
Abstract Mechanically interlocked molecules (MIMs) represent an exciting yet underexplored area of research in the context of carbon nanoscience. Recently, work from our group and others has shown that small carbon nanotube fragments—[n]cycloparaphenylenes ([n]CPPs) and related nanohoop macrocycles—may be integrated into mechanically interlocked architectures by leveraging supramolecular interactions, covalent tethers, or metal‐ion templates. Still, available synthetic methods are typically difficult and low yielding, and general methods that allow for the creation of a wide variety of these structures are limited. Here we report an efficient route to interlocked nanohoop structures via the active template Cu‐catalyzed azide‐alkyne cycloaddition (AT−CuAAC) reaction. With the appropriate choice of substituents, a macrocyclic precursor to 2,2′‐bipyridyl embedded [9]CPP (bipy[9]CPP) participates in the AT−CuAAC reaction to provide [2]rotaxanes in near‐quantitative yield, which can then be converted into the fully π‐conjugated catenane structures. Through this approach, two nanohoop[2]catenanes are synthesized which consist of a bipy[9]CPP catenated with either Tz[10]CPP or Tz[12]CPP (whereTzdenotes a 1,2,3‐triazole moiety replacing one phenylene ring in the [n]CPP backbone).
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- Award ID(s):
- 2204123
- PAR ID:
- 10500078
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Within the field of mechanically interlocked molecules, catenanes have garnered much interest in the past few decades due to their chain‐like architecture of interlocked molecular rings. This interest stems from their unique properties and degrees of freedom that are distinct in comparison to traditional molecular architectures, a fact that makes catenanes potentially attractive building blocks in the construction of next‐generation polymeric materials. Most approaches to make unimolecular [n]catenanes are either low yielding or are laborious, often relying on multistep pathways for preparation and purification. Therefore, developing efficient syntheses for [n]catenanes remains an important challenge for chemists. Here, we describe a template‐directed one‐pot approach that overcomes the limitations of multistep syntheses by using simple, symmetrical phenanthroline‐based building blocks and CuAAC “click” chemistry to yield a series of unimolecular [n]catenanes. This methodology relies on simultaneous copper(I)‐based templation and click chemistry, ultimately resulting in a one‐pot synthetic strategy to make either a [2]catenane in high yield (82%) or a batch of well‐defined linear [2]–[5]catenanes (and trace amounts of a [6]catenane) in an 18% overall yield, depending on the rate of addition of the alkyne‐ and azide‐functionalized precursors (i.e., slowly or all at once). Such kinetic control represents a potential pathway toward the preparation of higher‐order [n]catenanes capable of further chain extension using very simple precursors.more » « less
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