Synthesis of Bisazacalix[n]pyridines and Their Complexation with C₆₀ and C₇₀

Abstract

Disulfane-linked bisazacalix[n]pyridines (n＝4, 7) were synthesized for the first time using a macrocyclic fragment coupling approach followed by post-macrocyclization photoreaction with ethanethioic acid and hydrolysis under basic conditions. The bis-macrocyclic compounds acted as strong receptors to form 1∶1 complex with C 60 and C 70 , giving a binding constant (K a(1∶1) ) up to 107000 L•mol -1 . The cooperation of two mono-macrocyclic improved binding affinity to fullerenes.

Nitrogen and Oxygen Bridged Calixaromatics: Synthesis, Structure, Functionalization, and Molecular Recognition

“…Based on fragment coupling approach, we have prepared a number of homologous azacalix[ n ]pyridines 8 – 14 ( n = 4–10). − Following the same procedures depicted in Scheme , employment of 2,6-diaminopyridine and 2,6-bis(methylamino)pyridine instead of 1 and 5 , respectively, leads to the formation of azacalix[4]pyridine 8 and azacalix[8]pyridine 11 in a total yield up to 53%. Under optimized conditions, [3 + 1] fragment coupling reaction gives selectively azacalix[4]pyridine 8 in 36% yield .…”

Substituted Corannulenes and Sumanenes as Fullerene Receptors. A Dispersion-Corrected Density Functional Theory Study

“…The search for molecular receptors for fullerenes has been a very attractive field of research in recent years . Several compounds have been explored with the goal of finding more effective and selective fullerene receptors. − A promising strategy to design new molecular receptors for fullerenes is using concave–convex complementarity. In this context, the curved polynuclear aromatic hydrocarbons, also known as buckybowls or fullerene fragments, seem to be ideal candidates because the concave surface of a buckybowl can fit adequately to the convex surface of fullerenes by concave–convex “ball-and-socket” interactions …”

Regulating the Conformation of Methylazacalix[6]pyridine by Oligonucleotide BCL-2 2345 and Its Recognition of Hydroxymethylpiperazinofullerene

“…The Job plot studies indicated that 1:1 complexation of MACP6 with C 60 -T occurred in both tris-HCl and tris-HCl-K + solution (Figures S8 and S9, Supporting Information). Previous study by Zhang et al has validated that MACP6 with flexible conformation in toluene showed high binding ability toward C 60 , with an association constant of (6.62 ± 0.22) × 10 4 M –1 . However, the high binding affinity of MACP6 to C 60 -T was also achieved in the presence of bcl-2 2345, which discounts the biological disadvantages associated with MACP6 and many other calixaromatics, such as their lack of aqueous solubility. − …”

“…Calixaromatics have attracted much attention on molecular recognition owing to their interesting conformations, cavity structures, versatile recognition properties, and functions. − Research on calixaromatics’ conformation has been promoted with the development of calixaromatic chemistry, which mainly focus on synthesis of inherently chiral forms of calxiaromatics − in terms of creation of chiral spaces for enzyme mimics and chiral recognition. − As for calixarenes, introducing an achiral substituent into the upper and/or lower rims may create molecular dissymmetry or asymmetry to form inherently chiral calixarenes. ,,,− However, such processes are generally delicate and difficult for the more flexible calixaromatics with a larger cycle. Therefore, control of the calixaromatics' conformation is still a challenging topic in the field of calixaromatics, although the conformational isomers determined by crystallography, , NMR, , and theoretical computation , have been widely studied. Additionally, chiral recognition by calixaromatics represents a relatively unexplored area due to the fact that calix[6]aromatics suffer from their reputation as highly flexible molecules. ,,, …”