Polyaromatic Calixarene Hosts: Calix[4]pyrenes

Abstract

Calixpyrenes, calix[4]arenes incorporating one or two pyrene moieties as a part of their hydrophobic cavities, have been prepared and fully characterized. Distally di-O-propoxy diether of the calix dipyrene, which exists in the pinched cone conformation with nearly parallel pyrene moieties, demonstrates strongly enhanced binding of an organic cation (N-methylpyridinium) compared with the analogous diethers of the parent calix[4]arene.

Figure 1

(a) A calix[4]arene molecule with possible substitution sites. (b) Selected examples of calix[4]arenes containing fused aromatic moieties. (c) New calix[4]pyrenes.

Figure 2

UV–vis (solid line) and emission (dashed line) spectra of (a) calix monopyrenes 7 (blue) and 1 (red) and (b) calix dipyrenes 11 (blue) and 2 (red). The spectra are taken in CHCl₃–CH₃CN (9:1) at 10 μM concentration.

Figure 3

X-ray structures of compounds 1, 11, 2, and host–guest complex 12⊂2. Hydrogen atoms, solvents, and anions are omitted for clarity.

Scheme 1. Synthesis of the Calix[4]pyrenes

Figure 4

(a) Aromatic region of the ¹H NMR spectra of compounds 10, 11, and 2. (b) Partial ¹H NMR spectrum of the guest 12 and its 1:1 mixtures with 11 and 2. The guest signals are indicated with asterisks.

Figure 5

DFT-computed guest, 12, exchange reactions between 14, 11, and 2.