Moon Hwan Cho

Calix[4]arenes bridged with two different crown ether loops: Influence of crown size on metal ion recognition

A series of calix[4]arene-bis-crownethers were synthesized in a fixed 1,3-alternateconformation with good yields by the reaction of amonocyclic calixcrown ether with multi-ethyleneglycoldi-p-toluenesulfonate in the presence of cesiumcarbonate. In the preparation of the monocycliccalixcrown ethers (1 and 2), the use ofpotassium carbonate as a base provided the best yieldregardless of the template concept. In two phaseextraction and competitive transport experiments forligand-metal complexation, calix[4]arene biscrown(5) provided the best selectivity for potassiumion. When a calixbiscrown ether (4) bearingdifferent sized crown ether loops coordinates to K+and Cs+, respectively, the changes of peak splittingpatterns and chemical shift on 1H NMR spectra aredependent on the complexed metal ion species.

A Lipophilic Acyclic Polyether Dicarboxylic Acid as Pb2+ Carrier in Polymer Inclusion and Bulk Liquid Membranes

An acyclic polyether dicarboxylic acid which contains n-tetradecyl alkyl substituents at the α-position of the carboxylic acid side-arm unit was prepared by the reaction of bisphenol and 2-bromoalkanoic acid in the presence of NaH as base with quantitative yields. This ligand was incorporated into chloroform bulk liquid membranes and into polymer inclusion membranes (PIMs) composed of cellulose triacetate as support and o-nitrophenyl octyl ether as plasticizer. Selective transport of Pb2+ was observed over transition metal ions in bulk liquid membranes. The PIM showed excellent stability and durability, with very high transport of Pb2+ from an acetate buffer source phase.

Synthesis and reactions of mono- and dipalladium complexes containing 2-thienyl and 2,5 (or 2,5%) -bridged thienylene (or dithienylene) ligand: new dipalladium complex formation connected by thioketene part via CS bond cleavage of thiophene

Oxidative addition reactions of 2-iodothiophene, 2-bromothiophene, and 2,5-dibromothiophene with equimolar Pd(CH2CHPh)L2 (LPMe3 and PEt3) at room temperature in THF produce mononuclear s-thienyl palladium(II) complexes trans-(2-C4H3S)PdX(PMe3)2 (XI, 1 ;X Br, 2) and trans-(5-Br(2-C4H2S))PdBrL2 (L PMe3, 3 ;L PEt3, 4). Reactions using 2,5-dibromothiophene, 2,5-diiodothiophene, and 5,5-dibromo-2,2%-bithiophene under 2:1 molar ratio in THF give thienylene (or dithienylene) bridged dipalladium complexes trans,trans-L2XPd(m-2,5-C4H2S)PdXL2 (L PMe3 ;X I, 5; Br, 6 ;L PEt3 ;X Br, 7) and trans,trans-(Me3P)2BrPd(m-2,5%-C4H2S-C4H2S)PdBr(PMe3)2 (8), in high yields. However, the equimolar reaction of 2,5-dibromothiophene with the Pd(0) complex results in formation of a dinuclear complex cis,trans-[(Me3P)2Pd(h 2 SCCHCHCBr)PdBr(PMe3)2 (9), in 56% yield via CS bond cleavage of the thiophene ring. All the complexes provided satisfactory IR and NMR ( 1 H, 31 P{ 1 H}, and 13 C{ 1 H}) spectra as well as elemental analyses. Molecular structures of 1, 7, and 9 were confirmed by X-ray crystallography. Treatment of 5 and 7 with CO (1 atm) results in CO insertion into one of the PdC bonds to give trans,trans-(Me3P)2IPdC(O)C4H2SPdI(PMe3)2 (10) in 94% and trans,trans-(Et3P)2BrPdC(O)C4H2SPdBr(PEt3)2 (11) in 23%, respectively. Also, treatments of 5 with n-butyl, tert-butyl, and cyclohexyl isocyanides result in its insertion into both of the PdC bonds to form iminoacyl Pd complexes trans,trans-(Me3P)2IPdC(NR)C4H2SC(NR)PdI(PMe3)2 (R n-Bu, 12; t-Bu, 13; cyclohexyl, 14), respectively.

Synthesis, characterization and properties of new fully n-alkylated 14-membered tetraaza macrocycles and their copper(II) complexes

Abstract New fully N-alkylated 14-membered tetraaza macrocyles 3,14-dimethyl- 3,14-dimethyl-2,6,13,17-tetraethyl-2,6,13,17-tetraazatricyclo[16.4.0.1.180.7.12]docosane (3) and 3,14-dimethyl-2,6,13,17-tetrakis(n-propyl)-2,6,13,17-tetraazatricyclo[16.4.01.180.7.12]docosane (4) have been prepared from direct reactions of 3,14-dimethyl-2,6,13,17-tetraazatricyclo [16.4.01.180.7.12]docosane (1) with appropriate alkyl bromides. The protonation constants of 3 and 4 were determined by a potentiometric method, and it was found that these ligands have a higher proton affinity than 1 and its tetra-N-methyl derivative (2). The new macrocyles react with the dehydrated copper(II) ion to form the stable complexes [Cu(L)]2+ ( L = 3 or 4 ) in an ethanol solution, but do not react with hydrated copper(II) or nickel(II) ions in the same solution. The effects of the N-alkyl groups on the protonation and complexation behaviours of the macrocycles and on the spectroscopic and redox properties of their copper(II) complexes are presented.

Synthesis of palladium and platinum complexes containing the multidentate ligands PPh2CH2(tBu)NNC(R)Q (R=H, Me; Q=2-pyridine, 2-thiophene, o-BrC6H4). Crystal structure of [PtMe{PPh2CHC(tBu)NNCMe(2-py)-κ3N,N′,P}] and [PdBr{PPh2CH2C(tBu)NNCHC6H4}-κ3C,N,P]

The reaction of PPh 2 CH 2 C( t Bu)NNCMe(NC 5 H 4 ) ( 1 ) with [Pt 2 Me 4 (μ-SMe 2 ) 2 ] gave the six-membered metallacycle [PtMe 2 {PPh 2 CHC( t Bu)NNCMe(2-py)-κ 2 N , P }] ( 4 ) which was converted into [PtMe{PPh 2 CHC( t Bu)NNCMe(2-py)-κ 3 N , N′ , P }] ( 5 ) at elevated temperature. Treatment of the methyl platinum complex 5 with an excess of MeI gave [PtMe 2 I{PPh 2 CHC( t Bu)NNCMe(2-py)-κ 3 N , N′ , P }]. A similar reaction of PtMe 2 (cod) with [PPh 2 CH 2 C( t Bu)NNC(HSC 4 H 3 ] ( 2 ) also afforded PtMe 2 {PPh 2 CH 2 C( t Bu)NNC(H)SC 4 H 3 -κ 2 N , P } ( 7 ). The prolonged heating of 7 led to decomposition rather than the cycloplatination product. The treatment of 2 with PtCl 2 (cod) in the presence of NEt 3 gave the deprotonated platinum(II) complex [Pt{PPh 2 CHC( t Bu)NNC(H)SC 4 H 3 -κ 2 N , P } 2 ] ( 8 ) containing an ene-hydrazone backbone. The cyclopalladated metallacycle [PdBr{PPh 2 CH 2 C( t Bu)NNCHC 6 H 4 }-κ 3 C , N , P ] ( 9 ) has been prepared by the oxidative addition of the o -halo-substituted phosphino hydrazone derived from PPh 2 CH 2 C( t Bu)NNC(H)( o -BrC 6 H 4 ) ( 3 ) to Pd 2 (dba) 3 . These new complexes have been characterized by 1 H-, 13 C-, and 31 P-NMR, and elemental analyses. The molecular structures of 4 , 5 and 9 have been determined by a single-crystal X-ray diffraction study.

Metal ion complexation by acyclic polyethers with lipophilic amide, thioamide, and amine end groups

A series of acyclic polyethers with lipophilic amide, thioamide, and amine end groups was synthesized. Metal ion transport across bulk liquid membranes and measurement of thermodynamic parameters for ligand-metal ion complexation by titration calorimetry show strong selectivity for complexation of lead ion over other metal ion species for the diamide ligand. Lead ion complexation by the acyclic polyether diamide involves the amide oxygens and silver ion coordination by a dithioamide analog involves the thioamide sulfurs. With a proper length of the ethereal linkage, the ligand wraps around the metal ion in a pseudocyclic fashion.

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.

Lead selective lipophilic acyclic diionizable polyethers.

A structural series of acyclic polyether dicarboxylic acids with n-butyl and n-tetradecyl alkyl side chains at the alpha-position of the carboxylic acid units, as well as varying lengths of the ethylene glycol ether linkage connecting two benzo units were prepared. In terms of stability constants, competitive solvent extraction and cation transport experiment by bulk liquid membrane toward transition metal ions, ligand 3 with a monoethylene glycol unit and n-butyl side chains provide the best selectivity for the lead ion.

Studies on the Complexes of N,N′-Bis[o-(diphenylphosphino)benzylidene]ethylenediamine with Transition Metal Ions

The thermodynamic parameters for the interaction of Cu2+, Ni2+, Co2+, Cd2+, andAg+ with the new title ligand have been determined by titration calorimetry in 50% THF–methanol (V/V) at 25 °C.Ag+ exhibited remarkably higher complexation selectivity.Ag+ and several transition metal ions have been transportedusing this ligand as carrier in a bulk liquid membrane. CompetitiveAg+–M2+ transport studies have also beencarried out for the same system. In this membrane transport study, high transport of Ag+ was observed in both single and competitiveAg+–M2+ transport studies. The complexformation of N,N′-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (P2N2) with silver,[Ag(P2N2)] (NO3), (1) is reported. Complex 1 has been characterized by X-ray crystallography. 1 ismonoclinic, space group P21/n (No. 14), with cell dimensionsa = 13.398(4) Å, b=12.577(5) Å, c = 21.521(4) Å, β =100.14(2) Å, V = 3570(2) Å3 and Z = 4.