• Journal of the Korean Chemical Society
• /
• v.55 no.6
• /
• pp.912-918
• /
• 2011

Tetraaza Schiff base macrocyclic ligands, $L^1$,$L^2$ and their transition metal chelates have been synthesized and characterized by elemental analyses, IR, electronic, EPR and $^1H$ NMR spectra, TGA and magnetic measurements. The molar conductance of one milli-molar solution of the complexes measured in DMF indicates that the divalent metal complexes are nonelectrolyte while those of trivalent metal ion, are 1:1 electrolytic in the same solvent. The reduction of Racah parameter from the free ion value confirms the presence of considerable covalence of metal ligand sigma bond in the Co(II) and Mn(II) complexes. The EPR spectra of Cu(II) complexes at room temperature shows axial symmetry indicating a $d_x{^2}_{-y}{^2}$ ground state with significant covalent character. The thermal analysis suggests that the complexes do not contain water molecules because only the metal is left as residue.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2001.05a
• /
• pp.129-132
• /
• 2001

감마선 조사에 의한 TCE와 PCE의 분해에 있어서, TCE는 과산화수의 영향을 거의 받지 않았지만, PCE는 과산화수소의 농도증가에 따라 분해가 감소되었다. 이들의 원인을 밝혀내기 위해 과산화수소의 첨가에 따른 $\cdot$OH의 생성량 변화를 EPR/spin-trapping의 방법에 의해 확인한 결과, EPR의 DMPO-OH의 신호강도 조사에서 과산화수소를 첨가한 경우와 첨가하지 않은 경우 모두 차이가 거의 없었다. 따라서 감마선 조사에 과산화수소를 별도로 첨가해도 $\cdot$OH의 생성량 증가가 없는 것으로 보아, 방사선에 의한 TCE 분해에 있어 과산화수소의 첨가는 큰 영향을 주지 않는다는 것을 밝힐 수 있었다. 그러나 PCE의 경우는 향우 계속 연구될 예정이다.

• Bulletin of the Korean Chemical Society
• /
• v.7 no.2
• /
• pp.108-110
• /
• 1986

The solution epr spectra of ${\alpha}-1,2,3-[H_nPV(IV)V_2W_9O_{40}]^{(7-n)-}$were measured at various pH and three protonated species have been identified. The spectrum of $H_3PV(IV)Ⅴ_2$ consisting of 8 lines indicates that the V-OH-V bridge prevents effectively the electron transfer between the vanadium atoms. The spectrum of $H_2PV(IV)V_2$ consisting of 15 lines can be interpreted by assuming that the electron is hopping fast between the two vanadium atoms in the V-O-V sequence. The multi-line spectrum of $HPV(IV)V_2$ is interpreted as a poorly resolved 43-line spectrum which originates from the electron hopping among the three vanadium atoms with the forward and backward transition probabilities of 4:1 in the OH-V-O-V sequence.

• Bulletin of the Korean Chemical Society
• /
• v.10 no.1
• /
• pp.23-26
• /
• 1989

EPR spectra of the high-temperature superconductor YBa_2Cu_3O_{7-x}$ doped with ytterbium have been measured at 77-300K. The superconducting, orthorhombic phase shows a spectrum at g = 2.08 (Spectrum O). As the temperature is lowered, another line ascribable to $Yb^{3+}$ grows gradually at g = 3.31. The intensity of Spectrum O was determined using Yb as the internal reference. The semiconducting, tetragonal phase shows a spectrum at g = 2.06 (Spectrum T), different from Spectrum O. The origins of these spectra are discussed.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.7
• /
• pp.781-785
• /
• 1999

Ferrisilicates with MFI type structure were hydrothermally synthesized. The structural environments of iron in the ferrisilicates were characterized by XRD, SEM, IR, EPR, and ammonia-TPD. It has been shown that pH of the final gel mixture during the synthesis affects the crystal size, morphology, chemical composition and catalyticactivity. The results of the lattice parameters, IR, and EPR indicate the existence of a framework iron and the content of framework iron depends on pH of the synthesis gel. Finally, the catalytic activity of these zeolites was examined for the cyclohexane oxidation to cyclohexanol and cyclohexanone in the liquid phase. The conversion of this reaction was increased with increasing iron content of the framework lattice positions.

• Bulletin of the Korean Chemical Society
• /
• v.8 no.5
• /
• pp.384-388
• /
• 1987

Modified Bloch equations were used to simulate the solution EPR spectra of mixed-valence heteropolyanions containing vanadium(IV) and vanadium(V). Simulated are the 15-, 22-, 36- and 43-line spectra of $\alpha$-1,2-$[PV(IV)VW_{10})O_{40}]^{6-},\;[P_2V(IV)V_2W_{15}O_{62}]^{10-},\;[HP_2V(IV)V_2W_{15}O_{62}]^{9-}$ and $\alpha$-1,2,3-$[HSiV(IV)V_2W_9O_{40}]^{7-}$, respectively. The transition probabilities for the intramolecular electron transfer were determined from the simulations.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.12
• /
• pp.1320-1325
• /
• 1998

ZnGa2O4: Mn phosphors were prepared by a new chemical process, and their photoluminescence and electron paramagnetic resonance characteristics were investigated. The chemical method showed a low temperature formation of phosphors and a rod-type shape of particles. The strong ultraviolet emission was observed in the undoped ZnGa2O4 phosphor, while strong green emission in the Mn2+-activated ZnGa2O4 phosphor. The green emission intensity of the phosphor prepared by the chemical method was much stronger than that prepared by the conventional method. This difference with preparation methods was interpreted as due to the difference in the distribution of Mn2+ in the host lattice. From EPR results, it was explained that the line intensity of the undoped ZnGa2O4 is associated with the electrical conductivity of this material and the concentration quenching of green luminescence of ZnGa2O4: Mn at higher Mn2+ concentration is attributed to the coupling by exchange interaction between Mn2+ ions.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.7
• /
• pp.549-553
• /
• 1994

The 2-(dimethylaminomethyl)thiophene (dmamt) complexes with copper(II) chloride and bromide were prepared and characterized by optical, EPR, XPS spectroscopies and magnetic susceptibility measurements. The low-energy absorption band above 850 nm and the relatively small EPR hyperfine coupling constant ($A_{//}{\simeq}$125 G) indicate the pseudotetrahedral site symmetry around copper(II) ion both in Cu(dmamt)$Cl_2$ and Cu(dmamt)$Br_2$ complexes. The higher satellite to main peak intensity of Cu $2P_{3/2}$ core electron binding energy in XPS spectra also supports the pseudotetrahedral geometry around the copper(II) ions having $CuNSX_2$ chromophores. The distortion from square-planar to pseudotetrahedral symmetry is likely to arise from the steric hindrance of the bulky dmamt ligand in the complex. Magnetic susceptibility study shows that these compounds follow Curie-Weiss law in the temperature range of 77-300 K with positive Weiss constant exhibiting the ferromagnetic interaction between copper(II) ions in solid state.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.358-361
• /
• 1995

We have investigated the quasi-two-dimensional magnetism for the layered transition metal compound (C/sub n/H/sub 2n+1/NH/sub 3/)/sub 2/CuCl/sub 4/ (n=10, 14) in the high temperature regions by means of EPR (Electron Paramagnetic Resonance) and SQUID measurements. As a result, the magnetic transitions were reflected in the EPR linewidths and the magnetic suceptibilities in a sensitive manner. Fluctuations of the magnetic susceptibility and a similar variation of the .DELTA. g =(g/sub .parallel. -/g/sub .perp. /)g/sub .parallel. / value were also observed around the structural phase transition temperatures.

• Proceedings of the PSK Conference
• /
• 2003.10b
• /
• pp.133.2-134
• /
• 2003

The major hurdle of conventional chemotherapeutics is the toxicity to normal tissue. The possible therapeutic advantage(s) of nano-particle encapsulated chemotherapeutics (nano-molecules) may be the enhanced permeability and retention (EPR) effect. Nano-molecules with increase volume may incorporated into the tumor tissue selectively, which is composed of rather sparse structure. EPR effect may cause of increased effectiveness with lower tixicity to normal tissue of nano-chemotherapeutics. (omitted)