Cycloparaphenylene Lemniscates and Trefoils

Abstract

A number of variants of the recently synthesized cycloparaphenylene lemniscates G have been explored at ωB97X-D/6-311G­(d). Lemniscates with four to eight phenyl rings in each loop having the N–N, CC, or B–N bond as the linkage all exhibit the figure-eight shape. Their ring strain energies (RSEs) are relatively independent of the nature of the linkage bond, but the RSE does systematically decrease with the increasing size of the loop. Selective nitrogen substitution into the ortho positions of the aromatic rings allows for the rings to become coplanar; this manifests in a more ribbon-like structure of the lemniscates. It also reduces the RSE of the lemniscates. Similarly, nitrogen substitution into the recently synthesized cycloparaphenylene trefoil E creates a more ribbon-like structure with reduced RSEs.

Electronic Current Density Induced by Uniform Magnetic Fields in Clarenes

“…Indeed, clarenes have been computed to be the energetically most stable forms among a large family of looped polyarenes, [20] suggesting that they would be appealing targets for future synthetic work owing to their unique structure and properties. A fully consistent result was reported in a thorough investigation of [12]circulene isomers [30] . Coming now to magnetic properties, it can be expected that, for Clar structures, Clar sextets will give disjoint local vortices of magnetically induced current, as actually verified by direct computation of the currents, [31–33] or guessed from the exaltation of the induced magnetic field [34,35] …”

Exploration of the Solid-State Sorption Properties of Shape-Persistent Macrocyclic Nanocarbons as Bulk Materials and Small Aggregates

“…Being composed entirely of aromatic phenylene rings, we speculated that the fascinating class of CPPs − shape-persistent macrocyclic nanocarbonsprovides a unique opportunity to manipulate solid-state arrangements by molecular design while maintaining the molecular properties, i.e., the radially oriented π-systems and macrocyclic cavity sizes. By changing the connectivity of the phenylene units in hoop-shaped [ n ]­CPPs, a new family of all-phenylene lemniscal nanocarbons, spiro­[ n – n ]­CPPs, , was prepared in which two macrocycles are fused in a central spiro-motif. With these novel macrocycles in hand, we were able to explore the impact on sorption and analyte uptake performance of preparing CPP compounds as either small aggregates versus bulk solids through a suite of X-ray crystallography, gas sorption, and quartz-crystal microbalance (QCM)-based analyte sensing measurements.…”

Figure-of-Eight Helicene Carbon Nanohoop with Möbius Topology

“…[14][15][16] One of the most intuitive ways to decrease the symmetry of a system is to induce chirality. [13] Examples of chiral carbon nanohoops that emerge by replacing a phenylene ring in the structure of CPPs by polycyclic aromatic hydrocarbons such as acenes, [13,[17][18][19] aromatic heterocycles, [20,21] and others [22][23][24] were investigated both theoretically and experimentally. This allows tuning the emission properties and could, in principle, lead to circularly polarized luminescence (CPL).…”

“…[27] Recently, their design has been slightly modified [28][29][30][31] and provided compounds with a promising CPL. The planar πelectron conjugation of these aromatic systems is topologically equivalent to the radial π-conjugation in carbon nanohoops, both characterized by even values of the so-called linking number (Lk, Figure 1), [20,21,25] which corresponds to the number of half-twists of the π-surface. As a consequence, all systems discussed above possess two orientable π-surfaces.…”