Byeongno Lee

Active digital microfluidic paper chips with inkjet-printed patterned electrodes.

Active, paper-based, microfluidic chips driven by electrowetting are fabricated and demonstrated for reagent transport and mixing. Instead of using the passive capillary force on the pulp to actuate a flow of a liquid, a group of digital drops are transported along programmed trajectories above the electrodes printed on low-cost paper, which should allow point-of-care production and diagnostic activities in the future.

Hydrogenation of nitriles with iridium-triphenylphosphine complexes

Reactions of cationic iridium(I)-COD (COD = 1,5-cyclooctadiene) complexes, [Ir(COD)(PhCN)(PPh3)]ClO4 (1), [Ir(COD)(PPh3)2]ClO4 (2) and [Ir(COD)(PhCN)2]ClO4 (3) with nitriles under H2 catalytically produce primary, secondary and tertiary amines. Hydrogenation of nitriles (RCN) gives HCl salts of amines (RCH2NH2HCl, (RCH2)2NH HCl) in CH2Cl2. Secondary and tertiary amines seem to be produced by the reactions of RCN with primary and secondary amines, respectively under H2 in the presence of catalysts. The hydrogenation in the presence of1 and2 is homogeneously catalyzed by soluble iridium-PPh3 complexes formed in the reactions of1 and2 with H2 and RCN whereas the hydrogenation in the presence of3 is heterogeneous by metallic iridium powders produced in the reduction of3 by H2.

Hollow nickel-coated silica microspheres containing rhodium nanoparticles for highly selective production of hydrogen from hydrous hydrazine

The synthesis of hollow nickel-coated silica microspheres containing rhodium nanoparticles (NPs) (Rh/Ni@SiO2) via thermal hydrolysis of urea using core–shell silica microspheres as templates is described. This dissolution-and-deposition method using urea as a precipitating agent provided uniform hollow microspheres composed of amorphous Ni(OH)2 and silica (SiO2) layers along with small amounts of Rh species even without etching; these hollow microspheres transformed to crystalline Rh/Ni@SiO2 microspheres after annealing at 750 °C under a reducing atmosphere. The formation of a hollow structure is dependent on the concentration of urea and unique dissolution behavior of the core–shell silica. The bimetallic Rh/Ni@SiO2 microsphere with a low Rh content (6.35 wt%) is a highly active catalyst for complete dissociation of hydrous hydrazine into hydrogen and nitrogen. Complete release of hydrogen from hydrous hydrazine was accomplished at 25 °C with a H2 selectivity of 99.4% and turnover number of 66. The used Rh/Ni@SiO2 catalyst, which was recovered by a magnet, was reused in subsequent reactions with virtually identical activity.

Synthesis of azines in solid state: reactivity of solid hydrazine with aldehydes and ketones.

Highly conjugated azines were prepared by solid state grinding of solid hydrazine and carbonyl compounds such as aldehydes and ketones, using a mortar and a pestle. Complete conversion to the azine product is generally achieved at room temperature within 24 h, without using solvents or additives. The solid-state reactions afford azines as the sole products with greater than 97% yield, producing only water and carbon dioxide as waste.

Isolation and structural characterization of the elusive 1:1 adduct of hydrazine and carbon dioxide

A solid hydrazine was isolated as a crystalline powder by reacting aqueous hydrazine with supercritical CO(2). Its structure determined by single crystal X-ray diffraction shows a zwitterionic form of NH(3)(+)NHCO(2)(-). The solid hydrazine is remarkably stable but is as reactive as liquid hydrazine even in the absence of solvents.

Regioselective catalytic hydrogenation of nitrogen rings of fused heteroaromatic compounds with an iridium-triphenylphosphine complex

Catalytic hydrogenation of fused heteroaromatic compounds, acridine, quinoline and quinaldine, selectively occurs at the nitrogen containing rings to give 9,10-dihydroacridine, 1,2,3,4-tetrahydroquinoline and 1,2,3,4-tetrahydroquinaldine in the homogeneous solution prepared from the reaction of [Ir(COD)(PPh3)(PhCN)]ClO4 (COD=1,5-cyclooctadiene) with H2 (5 atm) at 50°C, while isoquinoline and indole are not hydrogenated under the same experimental conditions. In the presence of the rhodium analog [Rh(COD)(PPh3)(PhCN)]ClO4 however, both isoquinoline and indole are also hydrogenated at the nitrogen containing rings, which is understood in terms of heterogeneous catalysis by metallic rhodium powders produced in the reduction of the rhodium compound under the same experimental conditions (50°C, 5 atm of H2).

Selective hydrogenation of the carbonyl group of α,β-unsaturated aldehydes to alcohols with iridium(I) complexes

Abstract The hydrogenation of C 6 H 5 CHCHCHO ( 1 ), C 6 H 5 CHC(CH 3 )CHO ( 6 ) and C 6 H 5 CHC(Cl)CHO ( 7 ) by Ir(ClO 4 )(CO)(PPh 3 ) 2 ( 2 ), IrCl(PPh 3 ) 3 ( 8 ), IrCl(CO)(PPh 3 ) 2 ( 9 ) and [Ir(CO)(PPh 3 ) 3 ]ClO 4 ( 10 ) occurs primarily at the carbonyl group to give unsaturated alcohols, C 6 H 5 CHCHCH 2 OH ( 5 ), C 6 H 5 CHC(CH 3 ) CH 2 OH ( 11 ) and C 6 H 5 CH  C(Cl)CH 2 OH ( 12 ) at 50°C under 9 atm of hydrogen. Compound 5 is isomerized to C 6 H 5 CH 2 CH 2 CHO ( 3 ) by 2 , 8 and 9 but not by 10 . The carbonyl group of 3 is further hydrogenated to produce the saturated alcohol, C 6 H 5 CH 2 CH 2 CH 2 OH ( 4 ) in the presence of 2 , 8 and 9 . The isomerizations: 5 → 3 by 10 , and 11 → C 6 H 5 CH 2 CH(CH 3 )CHO and 12 → C 6 H 5 CH 2 CH(Cl)CHO by 8 and 9 probably do not occur for steric reasons; the interaction between the internal olefinic group and the iridium with bulky ligands is hindered.

Evidence for light-induced oxygen exchange in the oxidation of liquid hydrocarbons on oxygen 18-labelled titanium dioxide

Titanium dioxide (TiO2) nanoparticles labelled with 18O isotopes were prepared via a sol–gel method with titanium alkoxide and 18O water precursors. The presence of 18O in the labelled TiO2 sample was confirmed using Raman spectroscopy and secondary-ion mass spectrometry. The photocatalysis of cyclohexane under UV light was investigated using 18O-labelled TiO2 as the catalyst; this reaction yielded 18O-containing cyclohexanone as the major product. The 18O content in the cyclohexanone product dramatically decreased with increasing reaction time. This isotopic experiment demonstrates that the oxygen atom in cyclohexanone originates from surface oxygen in 18O-labelled TiO2. Similar photoreactions performed with toluene and para-xylene as the hydrocarbon substrates afforded oxidation products containing 18O isotopes. The migration of oxygen atoms in 18O-labelled TiO2 into liquid hydrocarbons provides direct evidence for the involvement of the solid oxide in the interfacial reaction between a liquid substrate and surface oxygen in a solid catalyst.

One-pot solvent-free reductive amination with a solid ammonium carbamate salt from CO2 and amine

Many amines are liquid and their handling is inconvenient compared with the corresponding solids. We transformed a liquid (S)-(−)-1-phenylethylamine 1 to the corresponding neutral solid form 2 by reacting with carbon dioxide. We performed reductive amination of 2 with various aldehydes 3 under solvent-free conditions to provide secondary amines 5 in high yields.

Synthesis, reactions and catalytic activities of cationic iridium(I) complexes of cycloocta-1,5-diene

New cationic iridium(I) complexes, [Ir(cod)(PPh3)L]ClO41[cod = cycloocta-1,5-diene; L = PhCN, PhCHCHCN, CH2CHCN, CH2C(Me)CN, MeCHCHCN or CH2CHCH2CN co-ordinated through the nitrogen atom], have been prepared by the reactions of [IrCl(cod)(PPh3)] with AgClO4 in the presence of L. Reaction of [Ir(cod)(PPh3)(PhCN)]ClO41a with H2 gives the cis-dihydridoiridium(III) complex [IrH2(cod)(PPh3)(PhCN)]ClO42a where the two hydrides are trans to PhCN and an olefinic group of cod, respectively. Complex 2a is stable both in solution and in the solid state at low temperature and decomposes at 15 °C to give cyclooctane and unidentified Ir–cod complex(es). The nitrile (L) in 1 is readily replaced by both PPh3 and CO, while cod is replaced only by CO. In the presence of complexes 1, unsaturated alcohols such as CH2CHCH2OH, CH2CHCH(Me)OH and CH2CHCH(Ph)OH rapidly undergo isomerization to the corresponding saturated carbonyl compounds at room temperature. Complex 1a catalyses the hydrogenation of unsaturated aldehydes, PhCHCRCHO (R = H, Me or Cl) to give PhCHCRCH2OH, PhCH2CHRCHO and PhCH2CHRCH2OH under H2(pH2= 6 atm) at 50 °C.