Search

E-mail: kimhs@knu.ac.krReceived August 26, 2011, Accepted September 15, 2011Key Words : One-pot reductive amination, Chlorotriisopropoxytitanium(IV), 1,1'-Diacetylferrocene, Sodiumtriacetoxyborohydride1,1'-Disubstituted-ferrocenes, especially bearing chelatingnitrogen atoms, are an important class of ligands in organicsynthesis.

E-mail : kimhs@knu.ac.krReceived February 23, 2011, Accepted March 7, 2011Key Words : Fluorescence sensing, Cyanide, Copper, Thiazole, ChemosensorThe recognition and detection of anions is a field that hasattracted increasing interest in recent years due to the funda-mental importance of these species in many chemical andbiological processes.

A new highly selective receptor (3) based on an acridine-imidazolium functionalized cholestane for anion sensing was designed and synthesized. A binding study of 3 with various anions was assessed by UV-vis and fluorescence spectroscopies in dry CH3CN. Receptor 3 showed the highest selectivity toward hydrogen pyrophosphate (Ka = ).

E-mail: kimhs@knu.ac.krReceived March 11, 2011, Accepted March 24, 2011Novel chemosensors based on 2-(2'-hydroxyphenyl)quinoline were prepared and evaluated for sensing metalcations. The photophysical properties of chemosensors 1-3 were examined and their ion-selectivity wasevaluated by measuring their fluorescent emission responses to alkali, alkaline earth, and transition metal ions.Chemosensors 1, 2 and 3 show ratiometric and enhanced fluorescence changes with transitional metals that areefficient fluorescence quenchers, especially 3 has a high binding constant with Hg

eties such as coumarin may undergo intermolecular changes at the electronic level upon following the cation dipole interactions of the oxygen donors. Therefore the alterations in the fluore-scence spectra of fluorogenic macrocycles in the presence of ions would be a good measure of ion dipole interactions.

A series of facial amphiphiles 3,7-diaminocholestane were synthesized from 3,7-diketocholestane via 2 sequential reductive aminations and anion recognition was evaluated with acetate, chloride, bromide, fluoride and phosphate anions. The stereo-selective reductive amination protocol was utilized to synthesized facial amphiphiles afforded receptors in high yields. The molecular receptor 2 showed the highest binding constant with acetate in a 1:1 ratio.

The efficient synthesis of four mesitylene-based receptors 1-4 and their potentiometric response characteristics to alkali metal, alkaline earth metal, and transition metal ions, under various pH conditions are outlined. Receptor 1-based electrode exhibited more sensitive response to Ag + ion (49 mV/decade of range from 10 -6 to 10 -2 M) than the 2-based electrode (47 mV/decade of range from 3 x 10 -5 to 10 -2 M), while the 3- and 4-based ones revealed sub-Nemstian below 40 mV/pAg + . All electrodes showed substantial responses to Ag + ion under acidic condition, but there was almost nil-response to other transition metal ions (Fe 2+ , Co 2+ , Zn 2+ , Ni 2+ , Pb 2+ , Cd 2+ , Cu 2+ and Hg 2+ ). The association constant of receptor 1 toward Ag + ion, measured by 1 H NMR titration, showed the largest value (200 M -1 ) among the tested receptors. The results were interpreted with semi empirically-modeled structures.

Molecular tweezers based on chenodeoxycholic acid bearing different lengths of arm were synthesized and their anion binding affinities were evaluated by 1 H NMR, isothermal calorimetric titration, and ESI mass spectrometry. Molecular tweezer 6 showed a high selectivity toward H 2 PO 4 - over Cl - , Br - , I - , and CH 3 CO 2 - by 1 H NMR titration, whereas the association constant for F - revealed the largest value as determined by ITC. The selectivity of 6 towards F - was about 10 3 times higher than that of Cl - , H 2 PO 4 - , and CH 3 CO 2 - . ITC experiment of 6 with F - in a DMSO showed two binding modes; two sequential association constants K 1 = 2.77 × 10 5 M -1 and K 2 = 8.68 x 10 6 M -1 were found. These sequential bindings were confirmed by ESI mass spectrometry. 1: 1 and 1: 2 complexes of 6 and F - were found at m/z 868.08 and 884.04.

Synthesis of cholic acid-based tripodal receptor (1) and its high chloride ion affinity in comparison with that of chenodeoxycholic acid (2) and lithocholic acid-based receptor (3) was achieved. Anion binding affinities of the receptors were evaluated NMR and ITC titrations. Tripodal receptor 1 showed a selective affinity for over , , , and . The selectivity of 1 for is about 3 times that of , and 17 times that for .

Chemical Sensor Research Group, Department of Chemistry, Kwangwoon University, Seoul 139-701, KoreaReceived April 20, 2004A short and efficient synthesis, solvent extraction and potentiometric measurements of new thiazole-containingnaphtho-crown ethers are reported. The naphthalene moiety enhances the ammonium ion selectivity overpotassium ion. The selectivity of NH

Department of Applied Chemistry, Kyungpook National University, Daegu 702-701, KoreaReceived June 15, 2004Key Words : Molecular tweezer, Chenodeoxycholic acid, Urea receptor, Anion recognitionThe design and synthesis of anion receptors can interactwith biologically relevant anions is prominent research fieldof supramolecular chemistry.