• Bulletin of the Korean Chemical Society
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• v.4 no.2
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• pp.79-83
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• 1983

The structure of thiamphenicol, one of the congeners of chloramphenicol which is a well-known antibiotic, has been determined by single crystal x-ray diffraction techniques. The crystal structure was determined using diffractometer data obtained by the $2{\theta}:{\omega}$ scan technique with $MoK{\alpha}$ radiation from a crystal having space group symmetry $P2_{1}2_{1}2_{1}$, and unit cell parameters a = 5.779, b = 15.292 and c = 17.322 ${\AA}$ . The structure was solved by direct methods and refined by least squares to an R = 0.070 for the 2116 reflections. The overall V-shaped conformation of thiamphenicol revealed in this study is consistent with those from the crystallographic studies and the proposed models from the theoretical and nmr studies of chloramphenicol. However there is no intramolecular hydrogen bond and the propanediol moiety is fully extended in the thiamphenicol molecule, while the crystal structures of chloramphenicol show the existence of the hydrogen bond between the two hydroxyl groups of the propanediol moiety forming an acyclic ring. All of the thiamphenicol molecules in the crystal are linked by a threedimensional hydrogen bonding network.

• Journal of the Korean Chemical Society
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• v.63 no.1
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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.

• Bulletin of the Korean Chemical Society
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• v.7 no.5
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• pp.331-334
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• 1986

The crystal structure of thiamin tetrahydrofurfuryl disulfide, one of the ring-opened derivatives of thiamin, has been determined by the X-ray diffraction methods. The crystal is monoclinic with cell dimensions of a = 8.704 (1), b = 11.207 (2), c = 21.260 (3) ${\AA}$ and ${\beta}$ = 92.44 (2)$^{circ}$, space group P2$_{1}$/c and Z = 4. The structure was solved by direct methods and refined to R = 0.076 for 1252 observed reflections measured on a diffractometer. The molecule assumes a folded conformation in which the pyrimidine and the tetrahydrofurfuryl rings are on the same side of the ethylenic plane. The pyrimidinyl, N-formyl and ethylenic planes are mutually perpendicular to each other and the N(3)-C(4) bond retains a single bond character. The structure is stabilized by an intramolecular N(4'${\alpha})-H{\cdots}O(2{\alpha}$) hydrogen bond. The molecules are connected via N(4'${\alpha}$)-H{\cdots}(N3')$ and O(5${\gamma})-H{\cdots}(N1')$ hydrogen bonds, forming a two-dimensional hydrogen-bonding network. The tetrahydrofurfuryl ring is dynamically disordered. The overall conformation as well as the packing mode is very similar to that of thiamin propyl disulfide.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2603-2608
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• 2012

A novel mononuclear supramolecule of copper(II) has been synthesized with Ippyt ligand (Ippyt=3-(4'-imidazole phenyl)-5-(pyrid-2''-yl)-1,2,4-triazole) (1). Compound 1, namely [$Cu(Ippyt)_2(H_2O)_2$], has been characterized by single-crystal X-ray diffraction, IR spectrum, elemental analysis and thermogravimetric analysis. Structure determination reveals that the elongated-octahedral geometry is formed in the vicinity of the copper (II) atom being coordinated by four nitrogen atoms from two Ippyt ligands occupying the equatorial position and two oxygen atoms from two coordinated water molecules in the axial position, which together form the $N_4O_2$ donor set. Hydrogen bonding interactions between nitrogen and oxygen atoms result in the set up of a supramolecular network architecture. Biological properties including antibacterial activity and superoxide dismutase (SOD) mimetic activity of compound 1 have been investigated by agar diffusion method and the modified Marklund method, respectively. The results indicate that compound 1 exhibits a stronger antibacterial efficiency than the parent ligand and it also has a certain radical-scavenging activity.

• Polymer(Korea)
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• v.36 no.5
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• pp.617-621
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• 2012

PHEAs [${\alpha}$,${\beta}$-poly(2-hydroxyethyl-DL-aspartamides)], a class of poly(amino acid), have been widely studied as biodegradable and biocompatible polymers for potential biomedical and pharmaceutical applications. In this study, we investigated a homogeneous blend of PHEA with poly(N-vinyl pyrrolidone) (PNVP) and its semi-IPN (semi-interpenetrating polymer network) gels. Blend films were prepared by a solution casting method. The resulting blends were totally transparent over the whole composition ranges and the single $T_g$, changing monotonously with composition, was observed by DSC to confirm the miscibility between these two polymers. FTIR was used to discuss the possible hydrogen-bonding interaction between polymers. In addition, semi-IPN type gels were prepared by chemical crosslinking of PHEA/PNVP blend solution using hexamethylene diisocyanate (HMDI) as a crosslinking reagent. The prepared gel was characterized by their swelling property and morphology.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.126-126
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• 2017

Using first principles calculations we unveil fundamental mechanism of hydrolysis reactions of two hazardous chemicals $PCl_3$ and $POCl_3$ with molecular water clusters nearby. It is found that the water molecules play a key role as a catalyst significantly lowing the activation barriers by transferring its protons to the reaction intermediates. Interestingly, torsional angles of molecular complexes at transition states are identified as a vital descriptor on the reaction rate. Analysis of charge distribution over the complexes further reinforces the finding with atomic level correlation between the torsional angle and variation of the orbital hybridization state of P in the complex. Electronic charge separation (or polarization) enhances thermodynamic stability of the activated complex at transition state and reduces the activation energy through hydrogen bonding network with water molecules nearby. Calculated potential energy surfaces (PES) for the hydrolysis reactions of $PCl_3$ and $POCl_3$ depict their two contrastingly different profiles of double- and triple-deep wells, respectively. It is ascribed to the unique double-bonding O=P in the $POCl_3$. Our results on the activation free energy show well agreements with previous experimental data within $7kcalmol^{-1}$ deviation.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.308-314
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• 2018

Among the fuel cell electrolyte candidates in the intermediate temperature range, glass materials show stable physical properties and are also expected to have higher ion conductivity than crystalline materials. In particular, phosphate glass has a high mobility of protons since such a structure maintains a hydrogen bond network that leads to high proton conductivity. Recently, defects like volatilization of phosphorus and destruction of the bonding structure have remarkably improved with introduction of cations, such as Zr4+ and Nb5+, into phosphate. In particular, niobium has proton conductivity on the surface because of higher surface acidity. It can also retain phosphorus content during heat treatment and improve chemical stability by bonding with phosphorus. In this study, we fabricate niobium phosphate glass thin films through sol-gel processing, and we report the chemical stability and electrical properties. The existence of the hydroxyl group in the phosphate is confirmed and found to be preserved at the intermediate temperature region of $150-450^{\circ}C$.

• Molecules and Cells
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• v.25 no.3
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• pp.352-357
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• 2008

Osteoprotegerin (OPG) is a soluble decoy receptor that inhibits osteoclastogenesis and is closely associated with bone resorption processes. We have designed and determined the solution structures of potent OPG analogue peptides, derived from sequences of the cysteine-rich domain of OPG. The inhibitory effects of the peptides on osteoclastogenesis are dose-dependent ($10^{-6}M-10^{-4}M$), and the activity of the linear peptide at $10^{-4}M$ is ten-fold higher than that of the cyclic OPG peptide. Both linear and cyclic peptides have a ${\beta}$-turn-like conformation and the cyclic peptide has a rigid conformation, suggesting that structural flexibility is an important factor for receptor binding. Based on structural and biochemical information about RANKL and the OPG peptides, we suggest that complex formation between the peptide and RANKL is mediated by both hydrophobic and hydrogen bonding interactions. These results provide structural insights that should aid in the design of peptidyl-mimetic inhibitors for treating metabolic bone diseases caused by abnormal osteoclast recruitment.

• Korean Journal of Crystallography
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• v.11 no.2
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• pp.75-79
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• 2000

The complex [Cu(L)(H2O)2] (PDC)(1)(L=2,5,9,12-tetramethyl-1,4,8,11- tetraazacyclotetradecane;PDC=1,4-pyridinedicarboxylate) has been synthesized and characterized by X-ray crys-tallography. The compound 1 crystallizes in the triclinic space group P1, with a=7.553(1)Å, b=9.619(2)Å, c=10.692(2)Å, α=74.22(1)°, β=73.32(1)°, γ=78.70(1)°, V=710.1(2)Å3, Z=1,R1(wR2) for 2634 observed reflections of [I>2σ(I)] was 0.0854(0.2242). The compound 1 is interconnected to give a three-dimensional network through weak hydrogen-bonding interactions.

• Korean Journal of Crystallography
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• v.13 no.1
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• pp.12-16
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• 2002

The complex [Ni(L)](BDC)·4H₂O (1) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[16,4,O/sup 1.18/,O/sup 7.12/] docosane; BDC = 1,3-benzenedicarboxylate) has been synthesized and characterized by X-ray crystallography. Compound 1 crystallizes in the orthorhombic space group Pcnb, with a = 8.764(2) , b = 17.687(2) , c = 19.475(1) , V = 3018.7(8) ³, Z = 4, R₁, (wR₂) for 2148 observed reflections of [1>2σ(I) was 0.0822 (0.2236). Compound 1 is interconnected to give a three-dimensional network through weak hydrogen-bonding interactions.