Il Hwan Suh

Calix[4]arene dibenzocrown ethers as caesium selective extractants

A series of 1,3-dialkyloxycalix[4]arene dibenzocrown ethers were synthesized in the fixed 1,3-alternate conformation with good yields by the reaction of 1,3-dialkyloxycalix[4]arenes with dibenzodimesylate in the presence of caesium carbonate. The three dimensional 1,3-alternate conformation was confirmed by X-ray crystal structure. Upon two phase extraction, NMR studies on the ligand–metal complex, single ion and competitive ion transport experiments through a bulk liquid membrane, 1,3-dipropyloxycalix[4]arene dibenzocrown-6, in which two benzo groups are symmetrically attached to the crown-6 linkage, gave one of the most efficient and selective extractabilities for caesium ion over other alkali metal ions. From supported liquid membrane experiments using 1 and 3 as organic carriers, permeation coefficients of the caesium ion were estimated to be 0.42 and 0.27 cm h–1, respectively. The selectivity of caesium over sodium ion was observed to increase with permeation time.

Selective sensing of caesium ions by novel calix[4]arene bis(dibenzocrown) ethers in an aqueous environment

Calix[4]arene bis(dibenzocrown) ethers 3 and 4 were successfully synthesized in the fixed 1,3-alternate conformation in over 70% yield via the reaction of calix[4]arene with dibenzo dimesylates 6 and 7, respectively, in acetonitrile in the presence of caesium carbonate as base. Exhibiting typical 1H NMR spectrum patterns, 3 and 4 are in the 1,3-alternate conformation, which is confirmed by X-ray analysis. Among four synthetic compounds tested, 3 shows the best selectivity and efficiency for a caesium ion complexation over other alkali metal ions using the single flux method through a bulk liquid membrane system. Enhancement of the complexation ability is attributable to the flatness and lipophilicity of the ethereal linkages caused by introducing the dibenzo groups on the calix[4]arene moiety. Two phase extraction experiments using calix[4]arene bis(crown) ethers with caesium ions are found to give a 1∶1 ligand–metal complexation ratio.

Novel Calix[4]arene Dibenzocrown Ethers Bearing Lipophilic Alkyl Groups Symmetrically Branched

Abstract 1,3-dialkyloxycalix[4]arene dibenzocrown ether in which two lipophilic butyl groups are symmetrically attached were successfully synthesized in the fixed 1,3-alternate conformation (12 and 13) of which structure was characterized by X-ray crystal structure.

Novel Calix[4]arene Azacrown Ether

Abstract 1,3-diproyloxycalix[4]arene azacrown ether was successfully synthesized in the fixed 1,3-alternate conformation which was confirmed by a solid state structure.

Characterization and structures of intermediates in the reactivity of CpWOs3(CO)11(μ3-CTol) towards dihydrogen and water

Abstract Initial decarbonylation of CpWos3(Co)11(μ3-CTol) (1: Cp = η5-C5H5, Tol = p-C6H4Mc) with the Me3NO/MeCN followed by reaction with dihydrogen and water produces a dihydrido comlex CpWOs3(CO)10(μ3-CTol)(μ-H)2 (2), a ‘butterfly’ cluster with a 60 valence electron (VE), and an oxo comlex CpWOs3(CO)10(μ-O)(μ3-CTol) (4) respectively. Complex 2 reacts either with carbon monoxide to produce the starting alkylidyne complex 1 by reductive elimination of dihydrogen or with PPh3 to afford a 62 VE ‘butterfly’ complex. CpWOs3(CO)10(PPh3)(μ3-CTol)(μ-H)2 (6). Thermolysis of 2 in the presence of water gives a hydrido oxo alkylidene complex, syn-CpWOs3(CO)9(μ-O)(μ-CHTol)(μ-H) (3a), in which the totyl substituent on the alkylidene carbon is oriented syn to the μ-oxo ligand. Thermolysis of 4 at 110°C induces decarbonylation to give a tetrahedral alkylidyne complex CpWOs3(CO)9(μ-O)(μ3-CTol) (5), which is reversibly converted back to 4 upon exposure to carbon monoxide. Complex 5 reacts with dihydrogen to afford a mixture of two isomeric hydrido oxo alkylidene complexes, antiCpWOs3(CO)9(μ-O)(μ-CHToL)(μ-H) (3b,c). The syn-isomer 3a is also produced from a mixture of 3b and 3c by thermolysis in boiling toluene. Compounds 2, 3a,b,c, 4, 5, and 6 haven been isolated as crystalline solids and characterized by spectroscopic (IR, MS, 1H and 13CMMR) and analytical data. The structures of 2 and 6 have been determined by single crystal X-ray diffraction studies. Compound 2 crystallizes in the orthorhombic space group P212121 with unit cell parameters a = 14.18(1), b = 28.46(1), c = 13.59(3) A , V = 5484(13) A 3 and Z = 8. Compound 6 crystallizes in the monoclinic space group P21/n with unit cell parameters a = 19.298(2), b = 22.406(4), c = 9.364(1) A , β = 92.83(9)°, V = 4044.0(9) A 3 and Z = 4. Diffraction data were collected on a CAD4 diffractometer, and structures were refined to R = 0.0957 and 0.0510 for 2 and 6 respectively. Both 2 and 6 are based upon a ‘butterfly’ WOs3 metal core with a respective dihedral angle of 114.3(2)° and 113.6(4)° between the WOs(2)Os(1) and WOs(2)Os(3) planes. Each molecule consists of three Os(CO)3 units and a CpW(CO) fragment, except that the Os(1) center in 6 is additionally coordinated with PPh3. The μ3-alkylidyne caps unsymmetrically the respective WOs(2)Os(3) face of both complexes.

Synthesis and characterization of (CH3C(CH2PPh2)3)RhH(η2-C60)

Abstract The title complex, (triphos)RhH(η2-C60) (2) (triphos=CH3C(CH2PPh2)3), was prepared by the reaction (80°C, toluene) of C60 with a trihydride rhodium complex (triphos)RhH3 (1) in high yield (86%) as green crystals and characterized by spectroscopic (mass, 1H-, 31P-, and 13C-NMR) and analytical data. The molecular structure of 2 was determined by a single crystal X-ray diffraction study. The rhodium atom is octahedrally coordinated by three fac-phosphorus atoms, a hydrogen atom and an η2-C60 ligand. The cyclic voltammetric study of 2 reveals two reversible redox waves which are shifted to more negative potentials by ca. 290 mV compared to free C60, reflecting both metal-to-C60 π-back-donation effect and the electron-donating nature of the triphos ligand.

Cesium Complex of an Unsymmetrical Calix[4]crown-dibenzocrown-6

An unsymmetrical calix[4]-bis-crown ether having both conventional crown-6 and dibenzocrown-6 rings in a fixed 1,3-alternate conformation was synthesized with good yield by the reaction of a monocyclic calix[4]crown-6 with dibenzodimesylate in the presence of cesium carbonate. The cesium ion selectivity among alkali metal ions increased compared to symmetrical calix[4]-bis-crown-6. The solid state structureof the ligand-cesium complex illustrates a 1:2 complex ratio. On the contrary, insolution, e.g., extraction equilibrium and 1H NMR experiment gave a 1:1 complex ratio. From the result of the chemical shift change upon metal ion complex, the cesium ion seems to prefer the dibenzocrown loop to the conventional crown-6 ring.

Synthetic and tautomeric studies of 5-amino-2,3-dihydro-1,2,4-oxadiazol-3-one

5-Amino-2,3-dihydro-1,2,4-oxadiazol-3-one 2 was synthesized as an analogue of cytosine. Among the possible four tautomers it was established by spectroscopic methods and ab initio calculations that it exists as a lactam form 2b like cytosine. The NH is more acidic than NH2, thus it could be regioselectively mesylated and acetylated under basic conditions.

Picolyl-armed 1,3-alternate calix[4]areneazacrown ethers

A series of novel 1,3-alternate calix[4]arene-azacrown ethers with 2-picolyl, 3-picolyl, and benzyl groups on the nitrogen atom were synthesized by reaction of 1,3-alternate calix[4]arene-azacrown ether and aryl halide in the presence of triethylamine as base. Based on two-phase extraction, bulk liquid membrane, 1H NMR, and solid-state studies on this ligand–metal complexation, 2-picolyl-armed calixazacrown ether showed the highest selectivity for silver ion due to electrostatic interaction through effective three-dimensional encapsulation assisted by the nitrogen atom of the 2-picolyl group. p