Trichalcogenasupersumanenes and its concave-convex supramolecular assembly with fullerenes

Buckybowl Molecular Tweezers for Recognition of Fullerenes

Buckybowl tweezers are a relatively young research area closely associated with the development of non-planar polycyclic aromatic systems and supramolecular chemistry. Since the appearance of the first prototypes in the early 2000s, the tweezers have undergone evolutionary changes. Nowadays they are able to effectively interact with fullerenes and the results opened up prospects for development in the field of sensing, nonlinear optics, and molecular switchers. In the present study, examples of corannulene-based and other buckybowl tweezers for the recognition of C60 and C70 fullerenes were summarized and analyzed. The main structural components of the tweezers were also reviewed in detail and their role in the formation of complexes with fullerenes was evaluated. The revealed structural patterns should trigger the development of novel recognition systems and materials with a wide range of applications.

Heteroatom-Promoted Polyhexagonal Saddle-Shaped Molecular Structures and their Supramolecular Coassembly with C60

Molecules with curved architecture can exhibit unique optoelectronic properties due to the concave-convex π-surface. However, synthesizing negatively curved saddle-shaped aromatic systems has been challenging due to the internal structural strain. Herein, we report the facile synthesis of two polyhexagonal molecular systems, 1 and 2, with saddle shape geometry by judiciously varying the aromatic moiety, avoiding the harsh synthetic methods as that of heptagonal aromatic saddle systems. The unique geometry preferences of B, N, and S furnish suitable curvature to the molecules, featuring saddle shape. The saddle geometry also enables them to interact with fullerene C60 , and the supramolecular interactions of fullerene C60 with 1 and 2 modify their optoelectronic properties. Crystal structure analysis reveals that 1, with a small π-surface, forms a double columnar array of fullerenes in the solid state. In contrast, 2 with a large π-surface produces a supramolecular capsule entrapping two discrete fullerenes. The intermolecular interactions between B, N, S, and the aryl-π surface of the host and C60 guest are the stabilizing factors for creating these supramolecular structures. Comprehensive computational, optical, and Raman spectroscopic studies establish the charge transfer interactions between B-N doped heterocycle host and fullerene C60 guest.

Probing the Antiaromaticity and Coordination Chemistry of Bowl-Shaped Zinc(II) Norcorrole

Zinc norcorrole was prepared as its pyridine complex (ZnNc·pyridine) by metalation of freebase norcorrole. The ZnNc·pyridine complex is distinctly bowl-shaped, as demonstrated by both X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy. NMR spectroscopy showed characteristic ring current deshielding effects, with different magnitudes on either face of the bowl-shaped complex. Exchanging the pyridine ligand with the bidentate ligand DABCO results in the formation of a stable (ZnNc)2·DABCO sandwich complex, which was also characterized by crystallography and NMR spectroscopy. The NMR resonances of the axial ligands in all of the complexes demonstrate that the paratropic ring current in zinc norcorrole is approximately 40 nA/T, which is comparable in magnitude to the diatropic ring current in porphyrin. Analysis of the ligand-exchange processes on addition of DABCO to ZnNc·pyridine showed that ZnNc coordinates to axial nitrogen-containing ligands with approximately 1000-fold higher binding constants than analogous zinc porphyrins.

Supramolecular Chemistry of Sumanene

Sumanene is a buckybowl molecule that is continuously attracting the attention of the scientific community because of its unique geometrical and physicochemical properties. This Minireview systematically summarizes advances and considerations regarding the applied supramolecular chemistry of sumanene. This work highlights the major fields in which potential or real applications of sumanene molecule have been reported to date, such as the design of sumanene-containing functional supramolecular materials and architectures, sumanene-based drug-delivery systems, or sumanene-tethered ion-selective molecular receptors. An assessment of the current status in the applied supramolecular chemistry of sumanene is provided, together with an emphasis on the key advances being made. Discussion on those milestones that are still to be achieved within this emerging field is also provided.

Cycl[2,2,4]azine-embedded non-alternant nanographenes containing fused antiaromatic azepine ring

The development of non-alternant nanographenes has attracted considerable attention due to their unique photophysical properties. Herein, we reported a novel aza-doped, non-alternant nanographene (NG) 1 by embedding the cycl[2,2,4]azine unit into the benzenoid NG framework. Single-crystal X-ray diffractometry suggests saddle or twisted nonplanar geometry of the entire backbone of 1 and coplanar conformation of the cycl[2,2,4]azine unit. DFT calculation together with solid structure indicates that NG 1 possesses significant local antiaromaticity in the azepine ring. By oxidative process or trifluoroacetic acid treatment, this nanographene can transform into a mono-radical cation, which was confirmed by UV/Vis absorption, 1H NMR, and electron paramagnetic resonance (EPR) spectroscopy. The antiaromaticity/aromaticity switching of the azepine ring on 1˙+ from 1 enables the high stability of this radical cation, which remained intact for over 1 day. Due to the electron-donating nature of the nitrogen and the unique electronic structure, NG 1 exhibits strong electron-donating properties, as proved by the intermolecular charge transfer towards C60 with a high association constant. Furthermore, selective modification of NG 1 was accomplished by Vilsmeier reaction, and the derivatives 7 and 8 with substituted benzophenone were obtained. The photophysical and electronic properties can be tuned by the introduction of different electronic groups in benzophenone.

Recent advances in supramolecular fullerene chemistry

Fullerene chemistry has come a long way since 1990, when the first bulk production of C60 was reported. In the past decade, progress in supramolecular chemistry has opened some remarkable and previously unexpected opportunities regarding the selective (multiple) functionalization of fullerenes and their (self)assembly into larger structures and frameworks. The purpose of this review article is to provide a comprehensive overview of these recent developments. We describe how macrocycles and cages that bind strongly to C60 can be used to block undesired addition patterns and thus allow the selective preparation of single-isomer addition products. We also discuss how the emergence of highly shape-persistent macrocycles has opened opportunities for the study of photoactive fullerene dyads and triads as well as the preparation of mechanically interlocked compounds. The preparation of two- or three-dimensional fullerene materials is another research area that has seen remarkable progress over the past few years. Due to the rapidly decreasing price of C60 and C70, we believe that these achievements will translate into all fields where fullerenes have traditionally (third-generation solar cells) and more recently been applied (catalysis, spintronics).