• Journal of the Korean Ceramic Society
• /
• v.40 no.6
• /
• pp.513-518
• /
• 2003

La/sub 2/3-x/Li/sub 3x/□/sub 1/3-2x/TiO₃ compounds with x=0.13 and 0.12 were prepared by slow cooling (x=0.13) and rapid quenching (x=0.12) into the liquid nitrogen after sintering at 1350℃ for 6 h. Their crystal structure has been determined by Rietveld refinement of both the powder neutron and X-ray diffraction data. From neutron diffraction data, we found that the main phase was not tetragonal (P4/mmm), but trigonal (R3cH). The refinement of neutron diffraction for the slow cooled samples were in a good agreement with a new model; a mixture of trigonal (R3cH, 45.7 wt％), tetragonal (p4/mmm, 37.0 wt％), and Li/sub 0.57/Ti/sub 0.86/O₂(pbnm, 17.2 wt%), but the quenched sample was found not to contain tetragonal (p4/mmm). X-ray diffraction data couldn't be well fitted because of the Poor scattering factor of lithium ions and the similar reflection patterns among trigonal (R3cH), tetragonal (p4/mmm), and cubic (Pm3m). We also knew that one transport bottlenecks is destroyed by one La vacancy in the case of trigonal (R3cH).

• Bulletin of the Korean Chemical Society
• /
• v.13 no.5
• /
• pp.491-498
• /
• 1992

Chelating triphosphines were applied to freeze the fluxionality and to minimize the number of isomers found in the monophosphine analogues and this technique was proved to be useful. RuH(NO)$P_3$($P_3$; Cyttp, ttp and etp) complexes were characterized to have similar trigonal bipyramidal structures with linear NO groups. Cyttp prefers to have a meridional geometry while etp prefers a facial one and ttp complexes are mixture of these two isomers. The crystal structure of RuH(NO)(Cyttp) has been determined to have a distorted trigonal bipyramidal structure with a linear NO in the equatorial plane. The crystals are orthorhombic, space group $P_{nma}$, with unit cell dimensions a = 16.356(2), b = 20.474(2), c = 10.915(l) ${\AA}$, V = 3655 ${\AA}^3$, Z = 4, R = 0.035 and $R_w$ = 0.034 for the 2900 intensities with $F_o^2 >3{\sigma}(F_o^2)$ and the 208 variables.

• Applied Biological Chemistry
• /
• v.37 no.2
• /
• pp.124-129
• /
• 1994

The rate of hydrolysis of insecticidal $O,O-diethyl-{\alpha}-cyanobenzylideneamino-oxyphosphorothioate\;(Volaton^{\circledR})$ has been studied in 25% (v/v) aqueous dioxane. On the basis of solvent effect (pH 6.0; m=0.21, n=1.55, pH 12.0; m=0.42, n=3.14 & $|m|{\ll}|l|$), general base catalysis, hydrolysis product analysis, calculation of molecular orbital (MO) and rate equation, it may be concluded that the hydrolysis of Volaton proceeds through the $A_{AC}2$ mechanism via trigonal bipyramidal $(sp^3d^2)$ intermediate below pH 7.0, while above pH 9.0 the hydrolysis proceeds through the $B_{AC}2$ mechanism. Hydrolysis reactivity of Volaton depends on positive charge strength $(p{\gg}{\alpha}C_2)$ rather than steric hindrance. In the range between pH 7.0 and pH 9.0, these two reactions occur competitively.

• Korean Journal of Crystallography
• /
• v.15 no.1
• /
• pp.9-17
• /
• 2004

There are 25 space groups in the trigonal system. Eighteen out of them have a lattice letter P displaying only hexagonal axes, wherease the remaining seven rhombohedral space groups R3(146), $R\={3}$(148), R32(155), R3m(160), R3c(161), $R\={3}m$(166) and $R\={3}c$(167) are described with two corrdinate systems, first with hexagonal axes having three lattice points (0, 0, 0), (2/3, 1/3, 1/3), (1/3, 2/3, 2/3) and second with primitive rhombohedral axes. In this paper, the space group $R\={3}c$ is discussed and the crystal structure of a compound, tris(1,2,3,4-tetraphenylbuta-1,3-dienyl)cyclotriphosphazene, $C_{84}H_{60}N_3P_3$, belonging to the space group $R\={3}c$ is elucidated with both hexagonal and rhombohedral cells.

• Journal of the Korean Chemical Society
• /
• v.56 no.4
• /
• pp.440-447
• /
• 2012

Heteroleptic complexes of zirconium (IV) derived from bulky Schiff base ligands containing a sulphur atom and oximes of heterocyclic ${\beta}$-diketones of the general formula ZrLL' (where $LH_2=RCNH(C_6H_4)SC:C(OH)N(C_6H_5)N:CCH_3$, $R=-C_6H_5$, $-C_6H_4Cl(p)$ and $L^{\prime}H_2=R^{\prime}C:(NOH)C:C(OH)N(C_6H_5)N:CCH_3$, $R^{\prime}=-CH_2CH_3$, $-C_6H_5$, $-C_6H_4Cl(p)$ were prepared by the reactions of zirconium tetrachloride with disodium salts of Schiff bases ($L\;Na_2$) and oximes of heterocyclic ${\beta}$-diketones ($L^{\prime}\;Na_2$) in 1:1:1 molar ratio in dry refluxing THF. The structures of these monomeric zirconium (IV) complexes were elucidated with the help of elemental analysis, molecular weight measurements, spectroscopic (IR, NMR and mass) studies. A distorted trigonal bipyramidal geometry may be suggested for these heteroleptic zirconium (IV) complexes. The ligands (bulky Schiff base ligands containing a sulphur atom and oximes of heterocyclic ${\beta}$-diketones) and their heteroleptic complexes of zirconium (IV) were screened against A. flavus, P. aeruginesa and E. coli.

• Korean Journal of Crystallography
• /
• v.3 no.1
• /
• pp.31-36
• /
• 1992

6, 9-Difluoro-11, 21-dihydroxyl-16, 17-[(1methylehtylidene)bis(oxy)]-pregna-1, 4-diene-3, 20-dione (fluorocinolone acetonide) , C24H3OF106, trigonal, R3 (defined as a hexagonal lattice), a =b = 17.896 k, c: 18.365 k, V=5094.3 A', Z=9, 1 (MoK a) =0.7107 A, D=1.31 g/cm3, D.: 1.328 g/cm3 T=298 K, final R=0.050 for 1101 unique observed reflections. The molecule has conformational features in common with other corticosteroids. Three molecules related by 3-fold symmetry are involved in hydrogen bonding, forming a layer of molecules perpendicular to the c-axis.

• Bulletin of the Korean Chemical Society
• /
• v.8 no.1
• /
• pp.1-3
• /
• 1987

The crystal structure of $K_5Na_2[SbW_6O_{24}]{\cdot}12H_2O$ has been determined. Final R = 0.081 for 890 observed independent reflections collected by diffractometry. Crystal data as follows; trigonal, space group R3m, a = 9.794(1) ${\AA},\;{\alpha}$ = 84.72$(1)^{\circ}$, Z = 1. The heteropolyanion has a structure with point symmetry $D_{3d}$ (3m), of the ideal Anderson-type heteropolyanion. The Sb-W and W-W distances are 3.259(2) and 3.259(3) ${\AA}$. Three types of W-O ($W-O_t,\;W-O_b\;and\;W-O_c$) distances are 1.73(2), 1.95(4) and 2.20(3) ${\AA}$. The Sb-O distance is 1.97(3) ${\AA}$.

• Bulletin of the Korean Chemical Society
• /
• v.13 no.5
• /
• pp.498-503
• /
• 1992

The protonation of RuH(NO)(Cyttp) resulted in the formation of $[RuH_2(NO)(Cyttp)]^+$ which is characterized as a classical cis-dihydried complex. This complex is fluxional and the intramolecular process involving a molecular hydrogen complex is proposed. This mechanism was further supported by the reactivity of this complex toward neutral 2-electron ligands. On the other hand, it failed to detect the existence of $[RuH_2(NO)(etp)]^+$ probably due to instability of the complex but the crystal structure of $[Ru(PMe_3)(NO)(etp)]^+$ formed by the protonation of RuH(NO)(etp) followed by the addition of $PMe_3$ was determined to have a trigonal bipyramidal structure with a linear NO in the equatorial plane and a facial etp ligand. The crystals are monoclinic, space group P21/n, with unit cell dimensions a = 14.130(2), b = 21.026 (3), c = 14.760 (1) ${\AA}$, ${\beta}$ = 97.88 $(l)^{\circ}$ V = 4344 ${\AA}^3$, Z = 4, R = 0.046 and $R_w$ = 0.056 for the 4779 intensities with $F_o^2 > 3{\sigma}(F_0^2)$ and the 440 variables.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.7
• /
• pp.1038-1042
• /
• 2006

A new type of DTPA-bis-amides (L1-L4) and their Gd(III)-complexes of the type $[Gd(L)(H_2O)]{\cdot}nH_2O$ (5: L1; 6: L2; 7: L3; 8: L4) have been prepared and characterized by analytical and spectroscopic techniques. The X-ray crystal structure of 8 has been determined for structural confirmation. The coordination geometry adopts a tricapped trigonal prism geometry with L4 acting as a chelate octadentate and a water molecule in the coordination sphere. Crystals are monoclinic, $P2_1$, a = 14.468(3), b = 19.235(4), c = 13.527(2) $\AA$ $\beta$ = $107.245(3)^{\circ}$, V = 3595.2(11) $\AA^3$, Z = 4, $D_{calc}$ = 1.570. Significant increases in relaxivities are observed with 6 and 7 as compared with that of $Omniscan^{(R)}$, a commercial MR agent: R1 = 12.46 $mM^{-1}\;s^{-1}$, R2 = 8.76 $mM^{-1}\;s^{-1}$ for 6; R1 = 12.77 nm-1 s-1, R2 = 7.60 mM-1 s-1 for 7; R1 = 4.9 $mM^{-1}\;s^{-1}$, R2 = 4.8 $mm^{-1}\;s^{-1}$ for $Omniscan^{(R)}$. In the case of 5, however, both R1 and R2 are found to be lower to show 2.09 $mM^{-1}\;s^{-1}$, and 1.82 $mM^{-1}\;s^{-1}$, respectively.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.3
• /
• pp.245-249
• /
• 1994

NaMg[$Cr(C_2O_4)_3]{\cdot}10H_2O$ crystallizes in the trigonal space group P$\bar{3}$c1, with a=b= 16.969(3), c=12.521(3) ${\AA}$, ${\alpha}={\beta}=90^{\circ},\;{\gamma}=120^{\circ},\;{\rho}=1.734 \;gcm^{-3},\;{\mu}=6.46\;cm^{-1}$, Z=6. Intensities for 1062 unique reflections were measured on a four-circle diffractometer with Mo K${\alpha}$ radiation (${\lambda}=0.71069\;{\AA}$). The structure was solved by direct methods and refined to a final ${\omega}$R value of 0.084. X-ray crystal structure showed that magnesium ion appears to be occupied over two sites with the occupancy ratio of 2:1. The crystal possesses 10 water molecules instead of previously estimated 9 water molecules.