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 (where
- PAR ID:
- 10199464
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 11
- Issue:
- 35
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 9395 to 9401
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Tz denotes a 1,2,3‐triazole moiety replacing one phenylene ring in the [n]CPP backbone). -
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 (where
Tz denotes a 1,2,3‐triazole moiety replacing one phenylene ring in the [n]CPP backbone). -
Abstract Fluorescent probes are an indispensable tool in the realm of bioimaging technologies, providing valuable insights into the assessment of biomaterial integrity and structural properties. However, incorporating fluorophores into scaffolds made from melt electrowriting (MEW) poses a challenge due to the sustained, elevated temperatures that this processing technique requires. In this context, [n]cycloparaphenylenes ([n]CPPs) serve as excellent fluorophores for MEW processing with the additional benefit of customizable emissions profiles with the same excitation wavelength. Three fluorescent blends are used with distinct [n]CPPs with emission wavelengths of either 466, 494, or 533 nm, identifying 0.01 wt% as the preferred concentration. It is discovered that [n]CPPs disperse well within poly(ε‐caprolactone) (PCL) and maintain their fluorescence even after a week of continuous heating at 80 °C. The [n]CPP‐PCL blends show no cytotoxicity and support counterstaining with commonly used DAPI (Ex/Em: 359 nm/457 nm), rhodamine‐ (Ex/Em: 542/565 nm), and fluorescein‐tagged (Ex/Em: 490/515 nm) phalloidin stains. Using different color [n]CPP‐PCL blends, different MEW fibers are sequentially deposited into a semi‐woven scaffold and onto a solution electrospun membrane composed of [8]CPP‐PCL as a contrasting substrate for the [10]CPP‐PCL MEW fibers. In general, [n]CPPs are potent fluorophores for MEW, providing new imaging options for this technology.
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Curved aromatic hydrocarbons often display better solubility and more desirable electronic properties in comparison to their flat counterparts. Macrocyclic curved aromatics possess these traits as well as shape-persistent pores ideal for host-guest interactions. A quintessential macrocyclic curved aromatic molecule is the cycloparaphenylene, or [n]CPP. Our group has developed a new class of these carbon nanohoops, called [n+1]CPPs, that incorporate a strained alkyne (“+1”) into the carbon backbone. We have previously shown the [n+1]CPPs to be a promising new class of strain-promoted azide-alkyne cycloaddition click reagents. Herein, we show that the [n+1]CPPs can also be converted into pinwheel-like multi-pore large molecules via a straightforward and high yielding metal-mediated alkyne cyclotrimerization reaction. We provide insight into suitable metals for this transformation, the photophysics of these trimeric molecules, as well as their strain profiles and crystal packing.
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null (Ed.)The consequences of four-electron addition to [8]cycloparaphenylene ([8]CPP, 1 ) have been evaluated crystallographically, revealing a significant core deformation. The structural analysis exposes an elliptical distortion observed upon electron transfer, with the deformation parameter (D.P.) increased by 28% in comparison with neutral [8]CPP. The C–C bond length alteration pattern also indicates a quinoidal structural rearrangement upon four-fold reduction. The large internal cavity of [8]CPP 4− allows the encapsulation of two {K + (THF) 2 } cationic moieties with two additional cations bound externally in the solid-state structure of [{K + (THF) 2 } 4 ([8]CPP 4− )]. The experimental structural data have been used as a benchmark for the comprehensive theoretical description of the geometric changes and electronic properties of the highly-charged [8]CPP 4− nanohoop in comparison with its neutral parent. While neutral [8]CPP and the [8]CPP 2− anion clearly show aromatic behavior of all six-membered rings, subsequent addition of two more electrons completely reverses their aromatic character to afford the highly-antiaromatic [8]CPP 4− anion, as evidenced by structural, topological, and magnetic descriptors. The disentanglement of electron transfer from metal binding effects allowed their contributions to the overall core perturbation of the negatively-charged [8]CPP to be revealed. Consequently, the internal coordination of potassium cations is identified as the main driving force for drastic elliptic distortion of the macrocyclic framework upon reduction.more » « less