Synthesis and Photophysical Properties of Chalcophenes-Embedded Cycloparaphenylenes

Synthesis and Photophysical Properties of Silole-Fused Cycloparaphenylenes

Herein, we report the introduction of a silole unit into cycloparaphenylenes (CPPs), and two compounds [12]Si3CPP and [16]Si4CPP are obtained by a platinum- and gold-mediated cyclooligomerization strategy. Their optical and electronic properties are studied by UV-vis absorption and fluorescence spectra, which show red shifts and higher photoluminescence quantum yields (PLQYs) compared with the corresponding CPPs.

Host-Guest Chemistry in Binary and Ternary Complexes Utilizing π-Conjugated Carbon Nanorings

The carbon nanorings, possessing a radial π system, have garnered significant attention primarily due to their size-dependent photophysical properties and the presence of a unique curved π-conjugated cavity. This is evidenced by the rapid proliferation of publications. Furthermore, the integration of building blocks into CPP skeletons can confer [n]CPPs with novel and exceptional photophysical and electronic characteristics, as well as chiral properties and host-guest interactions, thereby augmenting the diversity of [n]CPPs. Notably, the curved π surface structures and concave cavity of carbon nanorings enable them to host aromatic or non-aromatic guests with a complementarily curved surface, resulting in interesting binary or ternary complexes. This review provides a comprehensive treatment of literature reports on binary and ternary complexes, focusing on both their host-guest interactions and properties. It is important to note that the scope of this review is limited to host-guest chemistry in binary and ternary complexes based on π-conjugated carbon nanorings.

Efficient manipulation of Förster resonance energy transfer through host-guest interaction enables tunable white-light emission and devices in heterotopic bisnanohoops

In this study, we synthesized and reported the heterotopic bisnanohoops P5-[8,10]CPPs containing cycloparaphenylenes (CPPs) and a pillar[5]arene unit, which act not only as energy donors but also as a host for binding energy acceptors. We demonstrated that a series of elegant FRET systems could be constructed successfully through self-assembly between donors P5-[8,10]CPPs and acceptors with different emissions via host-guest interaction. These FRET systems further allow us to finely adjust the donors P5-[8,10]CPPs and acceptors (BODIPY-Br and Rh-Br) for achieving multiple color-tunable emissions, particularly white-light emission. More importantly, these host-guest complexes were successfully utilized in the fabrication of white-light fluorescent films and further integrated with a 365 nm LED lamp to create white LED devices. The findings highlight a new application of carbon nanorings in white-light emission materials, beyond the common recognition of π-conjugated molecules.

A BN-Doped Cycloparaphenylene Debuts

The first example of a BN-doped cycloparaphenylene BN-[10]CPP was synthesized and characterized. Its reactivity and photophysical properties were evaluated in direct comparison to its carbonaceous analogues Mes-[10]CPP and [10]CPP. While the photophysical properties of BN-[10]CPP remains similar to its carbonaceous analogues, the electronic structure changes associated with the introduction of a 1,2-azaborine BN heterocycle into a CPP scaffold enables facile and selective late-stage functionalizations that cannot be accomplished with carbonaceous CPPs. Specifically, Ir-catalyzed hydrogenation of BN-[10]CPP selectively reduces the BN heterocyclic ring, which upon hydrolysis produces a rare example of a macrocyclic paraphenylene 6 incorporating the versatile ketone functionality within the macrocyclic ring.

Synthesis, Structure, and Photophysical Properties of m-Phenylene-Embedded Cycloparaphenylene Nanorings

Five m-phenylene-embedded cycloparaphenylenes m₃[9]CPP 1-5 were synthesized by the platinum-mediated cyclooligomerization strategy with high overall yields. The structures of m₃[9]CPP 1-3 were determined by X-ray diffraction analysis. Compared to [9]CPP, m₃[9]CPP 1 caused a significant blueshift in the UV-vis absorption and fluorescence spectra. This result shows that the radial π-conjugation is distorted and partially interrupted. The photophysical properties of m₃[9]CPP 1 were further tuned by the introduction of various substituents for m₃[9]CPP 2-5. Methoxy group substitution at m-phenylene did not change the photophysical properties significantly. Replacement of m-phenylene by tetrafluoro-m-phenylene achieved a significant blueshift. When the carboxyl group was embedded at m-phenylene or the methoxy group was embedded at p-phenylene, significant redshifts were observed with blue color emission. Theoretical calculations revealed that the decrease in the HOMO-LUMO gap in m₃[9]CPP 4 and 5 is favorable for the redshift of the fluorescence spectrum.

Synthesis, Characterization, and Solid-State Structure of [8]Cycloparaphenylenes with Inherent Chirality

We report here the synthesis of two [8]cycloparaphenylenes ([8]CPP) derivatives, 1 and 2, bearing a monosubstituted benzene moiety. The presence of the substituent implies a planar chirality for the monosubstituted [8]CPP 1 and 2, whose configuration is here described by applying the chirality descriptors pR and pS. Experimental evidence of this planar chirality has been obtained through ¹H VT NMR studies and by addition of Pirkle's reagent. This was confirmed by the X-ray crystal structure of 2, which represents an interesting example of solid-state structure of a monosubstituted [8]CPP derivative. Derivative 2 crystallizes in two monoclinic crystal forms (α and β), which show a herringbone motif. The [8]CPP ring of the α form encapsulates two dichloromethane molecules, held through C-H···π interactions, while in the β form, open channels are partially filled by highly disordered solvent molecules.