PubMed Health⌕ Search

Biomedical subjects

Kwan Mook Kim

Publications and source records attributed to Kwan Mook Kim.

At least 19 recordsLinked to original sources
PubMed2006

Flexibility of inorganic tennis ball structures inducing anion selectivity.

Inorganic tennis balls (ITBs), [[{Pt(betmp)(dach)}(2)Cu](2)(X)][X](3) (in which X=ClO(4) (-) (3), NO(3) (-) (4), Cl(-) (5) and Br(-) (6); dach=trans-1,2-diaminocyclohexane and betmp=bisethylthiomethylidenepropanedioate) and [[{Pt(dteym)(dach)}(2)Cu](2)(PF(6))][PF(6)](3) (7; dteym=1,3-dithiepane-2-ylidenemalonate), were prepared as crystals. Investigation of their X-ray crystal structures revealed that shapes of the cavities in ITBs show significant distortions that depend on the properties of the encapsulated anions. The CuCu* distance was observed to be longest in 7 and shortest in 5, the difference between them being 2.05 A. The flexibility of cavity structures of ITBs makes it possible to encapsulate various anions inside the cavity, while their distortions may be a reason for the difference in the encapsulating ability for anions, that is, anion selectivity. Especially, the distortions observed in 7 are so severe that the encapsulating ability of the cavity for PF(6) (-) is very low compared to other anions. The shapes of ITBs with ClO(4) (-) and BF(4) (-) ions inside their cavities are very similar; however, ClO(4) (-) is encapsulated by the cavity better than BF(4) (-), which is explicable by the difference of metal-anion interactions. This structural study on ITBs gives a clue to the origin of the anion selectivity of the cavity in ITBs previously investigated by (19)F NMR spectroscopy of the ITBs in methanol.

Anions↗
PubMed2006

Nonheme iron(II) complexes of macrocyclic ligands in the generation of oxoiron(IV) complexes and the catalytic epoxidation of olefins.

Mononuclear nonheme oxoiron(IV) complexes bearing 15-membered macrocyclic ligands were generated from the reactions of their corresponding iron(II) complexes and iodosylbenzene (PhIO) in CH(3)CN. The oxoiron(IV) species were characterized with various spectroscopic techniques such as UV-vis spectrophotometer, electron paramagnetic resonance, electrospray ionization mass spectrometer, and resonance Raman spectroscopy. The oxoiron(IV) complexes were inactive in olefin epoxidation. In contrast, when iron(II) or oxoiron(IV) complexes were combined with PhIO in the presence of olefins, high yields of epoxide products were obtained. These results indicate that in addition to the oxoiron(IV) species, there must be at least one more active oxidant (e.g., Fe(IV)-OIPh adduct or oxoiron(V) species) that effects the olefin epoxidation. We have also demonstrated that the ligand environment of iron catalysts is an important factor in controlling the catalytic activity as well as the product selectivity in the epoxidation of olefins by PhIO.

Alkenes↗
PubMed2005

Enantioselective recognition of 1,2-amino alcohols by reversible formation of imines with resonance-assisted hydrogen bonds.

A chiral aldehyde with three H-bond donating groups (2) has been synthesized. This aldehyde binds a variety of chiral 1,2-amino alcohols in benzene with the same sense of stereoselectivity. Computational and experimental data indicate that one imine bond, one resonance-assisted H-bond to the imine nitrogen, and two H-bonds to the alcoholic oxygen all play an important role in the stereoselective recognition. [structure: see text]

Journal Article↗
PubMed2005

A highly selective fluorescent chemosensor for Pb2+.

A new fluorescent sensor based on rhodamine B for Pb2+ was synthesized. The new fluorescent sensor showed an extreme selectivity for Pb2+ over other metal ions examined in acetonitrile. Upon the addition of Pb2+, an overall emission change of 100-fold was observed, and the selectivity was calculated to be 200 times that of Zn2+. The signal transduction occurs via of reversible CHEF (chelation-enhanced fluorescence) with this inherent quenching metal ion.

Journal Article↗
PubMed2005

Parallel mechanistic studies on the counterion effect of manganese salen and porphyrin complexes on olefin epoxidation by iodosylarenes.

Counterions of manganese(III) porphyrin complexes influence diastereoselectivity in cis-stilbene epoxidation and product distribution in cyclohexene epoxidation markedly. In the epoxidation of cis-stilbene by iodosylbenzene carried out in a solvent mixture of CH(3)CN and CH(2)Cl(2), trans-stilbene oxide is the major product in the reaction of manganese complexes bearing a ligating anion (i.e., Cl(-)), whereas cis-stilbene oxide is the dominant product in the reactions of manganese complexes bearing a poorly-ligating anion (i.e., CF(3)SO(4)(-)). In cyclohexene epoxidation, the yields of allylic oxidation products such as cyclohexenol and cyclohexenone are higher when the counterion of the manganese catalysts is Cl(-) than when the counterion is CF(3)SO(4)(-). The product selectivities are also dependent on the nature of iodosylarenes and the axial and porphyrin ligands of the manganese porphyrin catalysts. The observation that product selectivities are different depending on the iodosylarenes may indicate the involvement of multiple oxidants in oxygen atom transfer reactions. These results are compared with those observed in manganese salen-catalyzed epoxidation of olefins by iodosylarenes.

Journal Article↗
PubMed2004

Chiral shift reagent for amino acids based on resonance-assisted hydrogen bonding.

[structure: see text] A chiral aldehyde that forms resonance-assisted hydrogen bonded imines with amino acids has been developed. This hydrogen bond not only increases the equilibrium constant for imine formation but also provides a highly downfield-shifted NMR singlet for evaluating enantiomeric excess and absolute stereochemistry of amino acids.

Aldehydes↗
PubMed2003

Bis[(2,2-dimethyl-1,3-propanediamine-kappa2N,N')(piperidine-2-carboxylato-kappa2N,O)platinum(II)] sulfate.

The title compound, [Pt(C(6)H(10)NO(2))(C(5)H(14)N(2))](2)(SO(4)), crystallizes with two cations in the asymmetric unit. The two complex cations, which have a square-planar Pt(II) coordination, are chemically identical but differ slightly in the conformations of their amine groups. A neutral complex, viz. (2,2-dimethyl-1,3-propanediamine-kappa(2)N,N')bis(2-piperidinecarboxylato-kappaN)platinum(II), is shown to form in solution and to change rapidly into the title compound.

Journal Article↗
PubMed2003

A metal-centered hydrophobic pocket recognizing pyridine over piperidine.

Two external spaces of an inorganic tennis ball are a novel type of metal-centered hydrophobic pocket where two hydrophobic trans-(+/-)-1,2-diaminocyclohexane groups stand perpendicularly to and around the metal coordination plane. The space recognizes pyridine over piperidine, and a novel supramolecule was obtained using such pyridine recognition properties.

Copper↗
PubMed2003

New heterometallic coordination polymers self-assembled from copper(II) nitrate and (diamine)Pt(II)(pyridinecarboxylates)(2).

One-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) coordination polymers were prepared by self-assembly of binary metal complex systems, copper(II) nitrate and (en)Pt(II)(nic)(2) or (dmpda)Pt(II)(isonic)(2) (en = ethylenediamine, dmpda = 2,2'-dimethyl-1,3-propanediamine, nic = nicotinate, and isonic = isonicotinate), in aqueous solutions. Equimolar reactions of copper(II) nitrate with (dmpda)Pt(II)(isonic)(2) and (en)Pt(II)(nic)(2) resulted in 1-D ([(dmpda)Pt(isonic)(2)Cu(OH(2))(3)](NO(3))(2))(n)() (1) and 2-D ([(en)Pt(nic)(2)Cu(OH(2))](NO(3))(2))(n) (2), respectively, but the reaction of (en)Pt(II)(nic)(2) with excess copper(II) nitrate gave 3-D ([((en)Pt(nic)(2))(3)Cu(5)(OH)(2)(OH(2))(6)](NO(3))(8))(n) (3). The local structure of crystal 1 has a mononuclear copper unit, 2 has a dinuclear copper unit with a Cu-Cu distance of 2.659(5) A, and 3 has a pentanuclear copper unit. The methyl groups of the dmpda ligand are located in the space between two isonicotinate ligands of 1, which is presumed to be an important factor to determine the final structure of the crystal formed by self-assembly. Magnetic behaviors of crystals 1-3 examined in the temperature range of 4-300 K appear to be governed by the local structures around the copper(II) ions and do not indicate any significant long-range magnetic exchange interactions along the polymeric chain.

Journal Article↗
PubMed2002

A 20-A-thick interwoven sheet consisting of nanotubes.

Slow diffusion of AgNO3 with Me2Si(4-Py)2 yields an interwoven 2-nm-thick sheet consisting of the building block [Ag3(Me2Si(4-Py)2)4](NO3)3.H2O. The interweaving induces unique nanotunnels with a 16 x 18 A2 cross section with a 7 x 8 A2 square pore. The anion NO3- of the skeletal sheet can be reversibly exchanged with appropriately sized anions without the collapse of its structural integrity. The compound has a melting point (140 degrees C) and exists as the first 2D ionic liquid up to 193 degrees C.

Journal Article↗