A novel mono-ionizable receptor 2 possessing three aminopyridyl and one carboxylic group in 1,3-alternate conformation based on thiacalix[4]arene, confirmed by single crystal X-ray analysis, was prepared. For competitive solvent extraction of alkali metal (Na+, K+ and Cs+) and some transition metal (Cu2+, Zn2+, TI+, Ag+) cations from aqueous solutions into chloroform, it was found that the introduction of proton-ionizable group (carboxylic acid moiety) into the aminopyridyl-thiacalix[ 4]arene derivative could further improve its Ag+ extractability with high selectivity.

A series of 1,3-alternate conformation thiacalix[4]arenes containing different isomeric aminopyridyl pendent arms have been synthesized. It was found that their self-assembly behaviors and complexation properties strongly depended on the structures of aminopyridyl pendent arms. The crystal structures demonstrate that tetra(meta-aminopyridyl)-thiacalix[4]arene motif is capable of forming intramolecular hydrogen bondings between the sp2 nitrogen donors in the meta position of the aminopyridyl groups and the facing amide N–H of the adjacent aminopyridyl groups, and self-assembles via C-H/O weak hydrogen bondings and C-H/p interaction to generate a double stranded rectilineal networks. By contrast, in the case of tetra(para-aminopyridyl)-thiacalix[4]arene, the presence of para-aminopyridyl units enables the formation of N-H/N strong hydrogen bondings between the individual molecules leading to the solid-state structure with water-bridged double strands. Their complexation properties had been also studied by measurement of the stability constants for their complexation in a range of metal cations and investigation of their binding models via 1H NMR titration and ESI-MS experiments. It was found that the three ligands exhibited high and selective extractability toward Agþ, and their stoichiometry of ligand to Agþ was 1:1, while the meta-aminopyridyl derivative showed the best extraction capacity and possessed the most efficient binding sites.

As bifunctional reagents, bis(tosyloxyethoxy)benzenes can react with p-tert-butylcalix[4]arene or p-tert-butylthiacalix[4]arene to afford intramolecularly bridged (1+1) or intermolecularly bridged (2+2) products. It was found that the bridging pattern strongly depended on the structure of bis(tosyloxyethoxy)benzene and the kind of calixarene. For the ortho-isomer of bis(tosyloxyethoxy)benzene, intramolecularly bridged calix[4]arene and thiacalix[4]arene were the main products. For the para-isomer, the bridging reaction was in a (2+2) fashion. As for the meta-isomer, double thiacalix[4]arene and intramolecularly bridged calix[4]crown were synthesized.

Detection of aromatic amines without derivatization was carried out using a new solid-phase microextraction fiber coated with 25,27-dihydroxy-26,28-(10,100-dioxo-40,70-diaza-30,80-dioxooctamethylene)-p-tert-butylcalix[4]arene (amide bridged-C[4]). The new fiber shows excellent selectivity and sensitivity for the tested amines (aniline, o-toluidine, 2,4-dimethylaniline, 3,4-dimethylaniline, N-ethyl-m-toluidine, and N,N-diethylaniline). The coating has high thermal stability (up to 380 C) and solvent stability. Experimental conditions, such as extraction temperature and time, pH and ionic strength were optimized. The method proposed here shows good linearity and low detection limits ranged from 1.2 to 40 ng.L)1. Application of this method was demonstrated through the determination of aromatic amines in wastewater from a pharmaceutical plant.