Yuanyin Chen

The sol-gel technique to prepare calix[6]crown-containing organosilicon resins and their adsorption properties towards metal ions

Abstract Two organosilicon resins (PCA[6]C4 and PCA[6]C4-TAE) were prepared from p-tert.-butylcalix[6]-1,4-crown-4 (CA[6]C4) via condensation with 3-glycidoxypropyltrimethoxysilane (KH560) or reacting its derivative p-tert.-butylcalix[6]-1,4-crown-4 tetraethylacetates (CA[6]C4-TAE) with γ-aminopropyl-triethoxysilane (KH550), followed by copolymerization with tetraethoxysilane via the sol–gel process, respectively. The adsorption capacity of PCA[6]C4 and PCA[6]C4-TAE toward alkali metal ions (Li+, Na+, and K+), transition metal and heavy metal ions (Ni2+, Co2+, Cu2+, Pb2+, Ag+, and Hg2+) were determined and the thermodynamic and dynamic parameters of the resins toward Hg2+ was deduced.

Selective bridging of p-tert-butylcalix[6]arene with polyethylene glycol ditosylates

Abstract A convenient method for preparing various p - tert -butylcalix[6]crowns and related compounds has been developed. By refluxing p - tert -butylcalix[6]arene with ethylene glycol ditosylate or polyethylene glycol ditosylates using K 2 CO 3 as a base in acetonitrile, 1,2-ethylenecalix[6]arene, 1,3- and 1,4-calix[6]crown-3, 1,3- and 1,4-calix[6]crown-4, 1,4-calix[6]benzocrown-4, 1,2- and 1,3-calix[6]crown-5 were obtained selectively. A rather flattened (o, o, o, o, o, o) conformation, adopted by the constrained 1,4-calix[6]crown-3 at ambient temperature, was observed for the first time.

Syntheses of Lower-Rim-1,3-Crowned Calix[6]Arenes and their Complexation Abilities Toward Cations

Abstract An approach to lower-rim-1,3-crowned calix[6]arene and its derivatives in one-pot process has been accomplished. In the presence of very excess Na2C03 (27-150 equivalent per mole p-tert-butyleal ix[6]arene 1) in acetonitrile, the lower-rim-1,3-bridged calix[6]crown-3 (4), the bistosylethoxy-ethyl derivative of 4 (5), as well as the intermediate of 4, monotosylethoxyethyl p-tert-butylcalix[6]arene 3, were obtained in rational yields, the distribution of the three compounds varied with the amount of the base used and other selected experimental conditions. 4 exhibits high selectivity towards Li+. 3 may be the first example of ionophore with high Et2NH2+ selectivity.

Syntheses of Novel Tripodal Calix[n]cryptands (n = 4, 6) and Their Extraction Abilities toward Cations

The tripodal calixcryptands have been one of the scarcely explored fields in calixarene chemistry due to the difficulties in their preparation. The strategy presented in this paper shows that novel tripodal calixcryptands can be conveniently prepared by directly treacing p-tert-butylcalix[n]arenes (n = 4, 6) with a multi-functional polypode reagent, e.g. 1,1,1-tris(tosyloxyethoxyethoxymethyl)propane or tetrakis(tosyloxyethoxyethoxymethyl)methane, under selected conditions. The first example of 1,2,4-tripodal calix[6]cryptands has been prepared. Novel calix[6]crown and doublecalix[4]arenes were co-prepared. The extraction abilities of these novel calixcryptands toward several alkali metal ions, ammonium and alkylammonium ions are presented.

Molecular design and synthesis of a calix[6]crown-based lithium-selective ionophore

Abstract Several 1,4-bridged calix[6]arene tetraesters were prepared from 1,4- p-tert -calix[6]crown-4’s by etherifying with ethyl bromoacetate. It was found that the 1,4- p-tert -calix[6]crown-4 tetraethylester ( 3a ) and the 1,4- p-tert -calix[6]benzocrown-4 tetramethylester ( 4b) exhibit very high selectivity toward lithium and sodium ions, respectively. The ion selectivity is very sensitive to the structure of polyoxyethylene spacer and the R in the ester moiety.

Synthesis of doubly bridged p-tert-butyl-calix[6]arene containing hard and soft ion binding sites

Abstract A conformationally preorganized, C s -symmetrical p - tert -butyl-calix[6]-1,4-crown-4-2,6-dioxo-diazacrown-4 with hard and soft ion binding sites at the lower rim is synthesized. The binding sites may complex alkali metal ions or transition metal ions selectively.

A novel type of double-calixcrown: Spirobiscalix[4]crowns

Abstract The synthesis and complexation properties of a novel type of double-calixcrown in which two cone-conformational calix[4]crown subunits were linked via a spiro C-atom incorporated into poly(oxyethylene) chains were described.

Synthesis of p-tert-butylcalix[6]-1,4-2,5-bis-crowns

Abstract The synthesis and complexation properties of the first example of p-tert -butylcalix[6]-1,4-2,5-bis-crowns are reported. Their complexation abilities and selectivities are different from that of analogous calix[6]crown. Compound 2b exhibits high complexation selectivity towards n- PrNH 3 + .

Calix[4]arenes and double calix[4]arenes bridged via calixarene segments

Abstract New type of calixarenes 4 and double calixarenes 3 bridged via calixarene segments at the lower rim are described.

A SYNTHETIC METHOD FOR DISELENIDES UNDER PHASE-TRANSFER CONDITIONS

Abstract Diselenides were easily prepared in high yields by the alkylation of sodium diselenide on halides in water under phase-transfer conditions.