• Macromolecular Research
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• 제16권8호
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• pp.725-733
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• 2008

Polyimide (PI) multilayer thin films were prepared by spin-coating from a poly(amic acid) (PAA) and poly(amic acid) ammonium salt (PAAS). PI was prepared from pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) PAA. Different compositions of PAAS were prepared by incorporating triethylamine (TEA) into PMDA-ODA PAA in dimethylacetamide. PI multilayer thin films were spin-coated from PMDA-ODA PAA and PAAS. The PAAS comprising cationic and anionic moieties were spherical with a particle size of $20{\sim}40\;nm$. Some particles showed layers with ammonium salts, despite poor ordering. Too much salt obstructed the interaction between the polymer chains and caused phase separation. A small amount of salt did not affect the interactions of the interlayer structure but did interrupt the stacking between chains. Thermogravimetric analysis (TGA) showed that the average decomposition temperature of the thin films was $611^{\circ}C$. All the films showed almost single-step, thermal decomposition behavior. The nanostructure of the multilayer thin films was confirmed by X -ray reflectivity (XRR). The LF 43 film, which was prepared with a 4:3 molar ratio of PMDA and ODA, was comprised of uniformly spherical PAAS particles that influenced the nanostructure of the interlayer by increasing the interaction forces. This result was supported by the atomic force microscopy (AFM) data. It was concluded that the relationship between the uniformity of the PAAS particle shapes and the interaction between the layers affected the optical and thermal properties of PI layered films.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2003년도 High Temperature Superconductivity Vol.XIII
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• pp.38-38
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• 2003

• 통합자연과학논문집
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• 제2권2호
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• pp.69-72
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• 2009

Pentiptycenediacetylene is very useful precursor materials for the synthesis of conducting polymer materials. The incorporation of rigid three-dimensional pentiptycene moieties into conjugated polymer backbones would offer several design advantages. They prevent ${\pi}$-stacking of the polymer backbones and thereby maintain high fluorescence quantum yields and spectroscopic stability in thin films. The pentiptycenediactylene was synthesized and characterized by 1H- and 13C-NMR spectroscopy.

• Molecules and Cells
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• 제27권6호
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• pp.667-671
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• 2009

Visfatin (Nampt/PBEF) plays a pivotal role in the salvage pathway for $NAD^+$ biosynthesis. Its potent inhibitor, FK866, causes cellular $NAD^+$ levels to decline, thereby inducing apoptosis in tumor cells. In an effort to improve the solubility and binding interactions of FK866, we designed and synthesized IS001, in which a ribose group is attached to the FK866 pyridyl ring. Here, we report the crystal structure of rat visfatin in complex with IS001. Like FK866, IS001 is positioned at the dimer interface, and all of the residues that interact with IS001 are involved in hydrophobic or ${\pi}-{\pi}$-stacking interactions. However, we were unable to detect any strong interactions between the added ribose ring of IS001 and visfatin, which implies that a bulkier modifying group is necessary for a tight interaction. This study provides additional structure-based information needed to optimize the design of visfatin inhibitors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.473-473
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• 2011

In recent years, organic thin film transistors OTFTs based on conductive-conjugated molecules have received significant attention. We report a fabrication of organic single crystal nanowires that made on Si substrates by liquid bridge-mediated nanotransfer molding (LB-nTM) with polyurethane acrylate (PUA) mold. LB-nTM is based on the direct transfer of various materials from a stamp to a substrate via a liquid bridge between them. In liquid bridge-transfer process, the liquid layer serves as an adhesion layer to provide good conformal contact and form covalent bonding between the organic single crystal nanowire and the Si substrate. Pentacene is the most promising organic semiconductors. However pentacene has insolubility in organic solvents so pentacene OTFTs can be achieved with vacuum evaporation system. However 6, 13-bis (triisopropylsilylethynyl) (TIPS) pentacene has high solubility in organic solvent that reported by Anthony et al. Furthermore, the substituted rings in TIPS-pentacene interrupt the herringbone packing, which leads to cofacial ${\pi}-{\pi}$ stacking. The patterned TIPS-Pentacene single crystal nanowires have been investigated by Atomic force microscopy (AFM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and electrical properties.

• 대한화학회지
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• 제63권1호
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• pp.29-36
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• 2019

A potentially tetradentate Schiff base ligand, 2-((2-((pyridin-2-ylmethylene)amino)ethyl)amino)ethan-1-ol (PMAE), and its cadmium(II) complex, [$Cd(PMAE)I_2$] (1), were prepared and characterized by elemental analysis, FT-IR, Raman, $^1H$ and $^{13}C$ NMR spectroscopies and single-crystal X-ray diffraction. In the crystal structure of 1, the cadmium atom has a slightly distorted square-pyramidal geometry and a $CdN_3I_2$ environment in which the PMAE acts as an $N_3$-donor. In the crystal packing of the complex, the alcohol and amine groups of the coordinated ligands participate in hydrogen bonding with iodide ions and form $R^2{_2}(14)$ and $R^2{_2}(8)$ hydrogen bond motifs, respectively. In addition to the hydrogen bonds, the crystal network is stabilized by ${\pi}-{\pi}$ stacking interactions between pyridine rings. The thermodynamic stability of the isolated ligand and its cadmium complex along with their charge distribution patterns were studied by DFT and NBO analysis.

• Natural Product Sciences
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• 제25권2호
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• pp.115-121
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• 2019

Alzheimer's disease is a chronic neurodegenerative disorder with no curative treatment. The commercially available drugs, which target acetylcholinesterase, are not satisfactory. The aim of this study was to investigate the cholinesterase inhibitory activity of Solenostemma argel aerial part. Eight compounds were isolated and identified by NMR: kaempferol-3-O-glucopyranoside (1), kaempferol (2), kaempferol-3-glucopyranosyl($1{\rightarrow}6$)rhamnopyranose (3) p-hydroxybenzoic acid (4), dehydrovomifoliol (5), 14,15-dihydroxypregn-4-ene-3,20-dione (6), 14,15-dihydroxy-pregn-4-ene-3,20-dione-$15{\beta}$-D-glucopyranoside (7) and solargin I (8). Two of them (compounds 2 and 3) could inhibit over 50 % of butyrylcholinesterase activity at $100{\mu}M$. Compound (2) displayed the highest inhibitory effect against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with a slight selectivity towards the latter. Molecular docking studies supported the in vitro results and revealed that (2) had made several hydrogen and ${\pi}-{\pi}$ stacking interactions which could explain the compound potency to inhibit AChE and BChE.

• 분석과학
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• 제6권1호
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• pp.29-37
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• 1993

말단기에 페닐(B), 벤질(Bz), 피리딘(Py), 퀴놀린(Q) 또는 나프탈렌(Np), 그리고 에테르 사슬에 산소(O) 또는 황(S) 주개원자를 갖는 몇 가지 포단드를 합성하여 1가 양이온과의 결합특성을 NMR 적정법과 용매추출법으로 조사하였다. NMR 적정에 의하면 대부분의 포단드는 1가 양이온과 1:1 착물을 형성하며, 특히 은이온과의 상호작용에서 에테르 사슬의 황 원자는 안정도를 증가시키는 효과를 나타내었다. 또한 포단드를 이용하여 에테르 수용액층에서 클로로포름층으로 알칼리 금속, 은, 탈륨 및 암모늄 등의 피크린산 1가 양이온염을 추출하였다. 은이온에 대한 추출률은 $Q_2O_4$, $Q_2O_5$ 및 $BQO_5$와 같이 퀴놀린을 포함하는 포단드의 경우 각각 86.8, 86.6 및 48.0%였으나 나프탈렌을 갖는 $Np_2O_4$ 및 $Np_2O_5$에 의해서는 거의 추출되지 않았다. 한편, $Bz_2O_3S_2$(89.4%), $B_2O_2S_2$(76.8%), $B_2O_3S_2$(58.9%), $Py_2O_2S_2$(58.8%), $Py_2O_3S_2$(42.1%) 및 $B_2O_4S$(15.0%)의 경우, 황 원자와 벤질기를 갖는 $Bz_2O_3S_2$가 가장 큰 은이온 추출 선택성을 나타내었다. 이러한 결과는 HSAB 이론에 의한 황 원자와 은이온과의 강한 상호작용 뿐 아니라 페닐기 대신에 벤질기가 치환됨으로써 유연한 메틸렌기 공간에 의해 두 방향족 말단기 사이의 ${\pi}-{\pi}$ 스택킹 상호작용이 효과적으로 증가하기 때문이다. 추출계수는 안정도 및 추출률과 비슷한 경향성을 나타내었는데, 이로부터 추출계수에 주된 영향을 미치는 요인으로는 포단드의 구조와 밀접한 관계가 있는 안정도임을 알 수 있었다.

• 대한화장품학회지
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• 제45권2호
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• pp.139-150
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• 2019

자외선에 의해 자외선 차단 효율이 상승하는 선크림에 대한 연구를 수행하였다. Ethylhexyl methoxycinnamate (OMC)는 가장 널리 쓰이는 자외선 차단제이고, OMC에 대한 광안정성 연구는 오랫동안 수행되어왔다. OMC는 자외선에 의해 trans구조가 cis구조로 변하거나, dimer를 비롯한 광반응물을 생성하여 자외선 차단효율이 떨어진다고 알려져 왔다. 하지만 본 연구에서는 OMC나 isoamyl p-methoxycinnamate(IMC)와 같이 메톡시신나메이트 구조를 공유하는 자외선 차단제들이 실제 사용조건과 유사한 조건에서 자외선에 노출 시키고 잘 설계된 실험 방법으로 in vitro SPF 수치를 측정하였을 때 오히려 자외선 차단 효율이 증가하는 것을 발견하였다. 이것은 자외선에 의해서 생성된 광반응물과 OMC간의 ${\pi}-{\pi}$ stacking을 통한 ${\pi}-{\pi}^*$ 전이 에너지 변화(UV activated transition) 때문인 것으로 생각된다. 이 발견을 선크림 개발에 적용하기 위해서는 함께 사용되는 에몰리언트의 극성 및 상용성을 적절히 고려해야 한다. 상용성이 좋은 극성 에몰리언트를 포함하면 자외선에 의해 OMC가 광반응물을 생성하지 않기 때문에 발견의 효과가 감소하는 것으로 보인다. 이러한 작용 기전(UV activated SPF boosting)을 바탕으로 상업용 수준의 선크림을 제조하여 평가해보았다. 그 결과 자외선(2 MED)에 노출되었을 때 in vitro SPF 수치는 50.69에서 72.33으로 42.69%로 증가하였고 in vivo SPF 평가에서는 53.7을 얻어 같은 조건의 대조군의 선크림(SPF 34.4 이하) 대비 56.10% 이상 높게 측정되었다. 따라서 OMC와 IMC가 특정 조건에서 UV sensor처럼 작용하여, 자외선에 노출 되었을 때 자외선 차단 효율을 높일 수 있는 선크림을 제조할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.2917-2924
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• 2012

Four novel metal-organic complexes $[Cd_2(IP)_2(TBZ)_2(H_2O)_2]{\cdot}(H_2O)$ (1), $[Zn_4(IP)_4(TBZ)_4]{\cdot}2(H_2O)$ (2), $[Zn_2(BTC)(TBZ)_2(CO_2H)]$ (3), [Co(PDC)(TBZ)] (4) (where IP = isophthalate; TBZ = thiabendazole; BTC = 1,3,5-benzenetricarboxylate; PDC = pyridine-3,4-dicarboxylate) have been prepared and characterized by IR spectrum, elemental analysis, thermogravimetric analysis, and single-crystal X-ray diffraction. X-ray structure analysis reveals that 1, 2, and 3 are one-dimensional chain polymers, while 4 is a two-dimensional network polymer. The TBZ acts as a typical chelating ligand coordinated to the metal center in all complexes. The 1D chain architecture of 1 is constructed from isophthalates and cadmium atoms. A simultaneous presence of chelating, monodentate and bidentate coordination modes of IP ligands is observed in complex 2. In complex 3, the 16-membered rings are alternately arranged forming an infinite 1D double-chain structure. The 2D skeleton of 4 is formed by cobalt ions as nodes and PDC dianions as spacers, through coordination bonds. The hydrogen bonds and ${\pi}-{\pi}$ stacking play important roles in affecting the final structure where complexes 1 and 3 have 2D supramolecular networks, while complexes 2 and 4 have 3D supramolecular architectures.