Synthesis and Conformational Evaluation of p-tert-Butylthiacalix[4]arene-crowns

Abstract

Bridging of p-tert-butylthiacalix[4]arene afforded 1,3-dihydroxythiacalix[4]arene-monocrown-5 (3b), 1,2-alternate thiacalix[4]arene-biscrown-4 and -5 (4a,b), and 1,3-alternate thiacalix[4]arene-biscrown-5 and -6 (5a,b), depending on the metal carbonates and oligoethylene glycol ditosylates used. Starting from 1,3-dialkylated thiacalix[4]arenes, the corresponding bridging reaction gave 1,3-alternate, partial-cone, and cone conformers 10-19, depending on the substituents present. Temperature-dependent studies revealed that the conformationally flexible 1,3-dimethoxythiacalix[4]arene-crowns 10a-c exclusively occupy the 1,3-alternate conformation. Demethylation exclusively gave the cone 1,3-dihydroxythiacalix[4]arene-crowns (3a,c), which could not be obtained by direct bridging of thiacalix[4]arene. The different structures were assigned on the basis of several X-ray crystal structures and extensive 2-D (1)H NMR studies.

Thiacalix[4]arene’s Lower Rim Derivatives: Synthesis and Supramolecular Properties

“…[72][73][74] The aromatic rings form a cup-shaped structure with C 2v symmetry (so called, pinched cone PC conformer) where each free phenolic group interacts only with one of the adjacent oxygen atom of substituted aryl moieties (Figure 4c,d). There are many examples of similar structures in the Cambridge Structural Database: distally disubstituted p-tert-butylthiacalix [4]arenes containing substituents with different electronic and steric characteristics, such as methyl, [75] propyl, [71] butyl, [68] allyl, [76] phenacyl, [71] diethers CH 2 COEt with-and without tert-butyl grous on the upper rim, [77] cyanomethxy [78] as well as monocrown, [79] bisporphyrin, [80] biscalixarene [81] and disubsituted with different substituents macrocycle 86. [71] The differences in the spatial structure of disubstituted methylene and sulfur bridged macrocycle are also observed in the solution ( Figure 5).…”

mPW1PW91 Calculated Relative Stabilities and Structures for the Conformers of 1,3-dimethoxy-p-tert-butylthiacalix[4]crown-5-ether

“…16 A number of thiacalix [4]arene-crowns have already been reported by several groups, namely, 1,3-alternate thiacalix [4]arene-biscrowns, 17 bridged thiacalix [4]arene-monocrowns. [18][19][20] Thiacalix [4]arenes can adopt four different conformations as follows: cone, partial cone, 1,2-alternate, and 1,3-alternate.…”

“…This calculated outcome is in accord with the experimental result, where the 1,3-alternate was the only observed conformation without finding cone or partial-cone conformer. 16 The mPW1PW91/6 -31 + G(d,p) calculations in Table 7 suggest that the 13a_oo is found to be 2.4 and 5.9 kcal/mol more stable than the cone_oo and pc_oo conformers, respectively. And 13a_oo is 1.4 kcal/mol more stable than 13a_io.…”

In situ synthesis of Ag nanoparticles in aminocalix[4]arene multilayers

“…However, the struc- tural differences between 1 and 2 are the bridging sulfur atoms instead of methylene units. Because of the presence of four sulfur atoms instead of the bridge methylene groups, 1 has many novel features such as excellent coordination abilities toward transition metal ions [31][32][33]. On the other hand, 1 and 2 are multifunctional and electroactive due to the presence of p-amino and hydroxyl groups.…”