Ineffective OH Pinning of the Flipping Dynamics of a Spherical Guest within a Tight‐Fitting Tube

Abstract

A supramolecular/synthetic method has been devised to affix a sterically hindered substituent onto a fullerene guest encapsulated in a tubular host. A two‐wheeled complex of (C59N)‐(C59N) with a tubular host was oxidatively bisected to afford a C59N+ cation captured in the tube. The C59N+ cation in the tube was then trapped by ethanol or water, which led to an oxy substituent pinned on the guest. The guest motions within the tube were modulated by the pinned substituent, and up‐and‐down flipping motions were halted by an ethoxy substituent. A hydroxy substituent, however, was ineffective in halting the flipping motions, despite the tight‐fitting relationship between the tubular host and the spherical guest. Theoretical calculations of the dynamics revealed that the flipping motions were assisted by OH‐π hydrogen bonds between the guest and the carbon‐rich wall and that sliding motions of the OH group were also facilitated by deformations of the tube.

Akaike's Information Criterion for Stoichiometry Inference of Supramolecular Complexes

“…Previously, C 120 was examined as the dumbbell‐shaped guest for cylindrical hosts of [4]CC and its lengthened congener, [4]cycloanthanthrenylene ( [4]CA ). A series of 2 : 1 host–guest complexes was concluded via antemortem analyses with the Job plot in previous studies, [18, 19] and a similar dumbbell‐shaped guest of C 118 N 2 was likewise concluded to be a 2 : 1 complex with the [4]CC host by antemortem methods [20] . However, considering the unique structural divergency of the host and guest, [15] we noticed that the 1 : 1, 1 : 2 and 2 : 1 models should be examined for postmortem analyses of dumbbell‐and‐cylinder complexes.…”

“…Previous antemortem analyses of the dumbbell‐and‐cylinder complexes utilized a combination of fluorescence quenching titration and isothermal titration calorimetry (ITC) experiments [18, 19, 20] . For the postmortem analyses in the present study, we noticed that ITC data were superior for global fitting analyses of complexation processes that potentially involved two‐stage associations, [3, 22, 23] and fitting analyses were performed with the ITC data of three dumbbell‐and‐cylinder systems ( [4]CC +C 120 , [4]CA +C 120 and [4]CC +C 118 N 2 ) that were originally investigated for the antemortem analyses [18, 19, 20] . After fitting with three models ( 1 : 1 , 1 : 2 and 2 : 1 ), GOF was first evaluated with R 2 and χ 2 values (Table 1).…”

Akaike's Information Criterion for Stoichiometry Inference of Supramolecular Complexes

“…In this work, we scrutinized the relevant host–guest systems of our previous studies and found interesting systems to investigate for further development of postmortem analyses. The first set of examples adopted dumbbell‐shaped guests of fullerene dimers [18, 19, 20, 21] . Previously, C 120 was examined as the dumbbell‐shaped guest for cylindrical hosts of [4]CC and its lengthened congener, [4]cycloanthanthrenylene ( [4]CA ).…”

“… Association of the dumbbell‐and‐cylinder complexes before and after the postmortem analyses ( o DCB). The antemortem data are taken from preceding papers [18, 19, 20] . The postmortem analyses by AIC showed that 2 : 1 is the best model for these systems.…”

New thiophene-based conjugated macrocycles for optoelectronic applications

“…C 60 for instance, has a mean ball diameter of 7.1 Å, whereas C 70 has a short axis of 7.1 Å and a long axis of 7.9 Å. 115 However, due to the absence of alkyne spacers between several thiophene moieties in the macrocycles, both adopt elliptical-like structures. This could potentially discourage fullerene molecules filling the cavity due to steric reasons.…”