| Research Abstract |
Aminothiacalixarenes, new members of the thiacalixa[4]arene (TCA) family having amino functions at the lower rim, were prepared from sulfur-oxygenated derivatives of TCA by applying the chelation-assisted nucleophilic aromatic substitution (S_NAr) reaction to estimate their intrinsic abilities for developing novel functional materials.
1.Selective syntheses of tetraamino, 1,2-and 1,3-diamino, and monoamino TCAa were achieved by using the S_NAr reaction on tetra-O-methylsulfonyl-and sulfinylcalix[4]arenes by lithium amides as the key step. Conformational analysis of the substrates indicated that the methoxy groups in a cis relationship with at least one adjacent sulflinyl group selectively underwent the S_NAr reaction.
2.Inclusion behavior of tetraamino TCA was investigated by crystallizing the host molecule from a series of solvents. It was found that the compound selectively formed 1:1 complexes with acetonitrile and dichloromethane. The acetonitrile complex adopted a cone conformation, while the host molecule crystallized out in a 1,3-alternate information from methanol without forming any inclusion complex, indicating that the complexation was accompanied by the conformational change of the host molecule (induced fit to the guest molecule).
3.Complexation ability of tetraamino TCA was investigated by solvent extraction experiments. It was found that tetraamino TCA served as a highly specific extractant for Au(III) and Pd(II) ions. The X-ray crystallographic analysis of a Pd(II) complex indicated that tetraamino TCA ligated is the metal ion with the bridging sulfur atoms and deprotonated amino functions. On the other hand, 1,2-diamino TCA was found to flexibly ligate to soft and hard metal ions by changing the ligation site (NH_2,OH).
4.Derivatization of the amino TCAs gave tetra(N-ethoxycarbonylmethyl) and bis(salicylideneamino) derivatives. The amino groups of amino TCAs were displaced with iodine atoms via the diazonium salts.
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