Quantitative Determination of Sodium Dodecatungstosilicate Speciation by 183W Nuclear Magnetic Resonance Spectroscopy

The speciation and equilibria of sodium dodecatungstosilicate has been determined using 183W nuclear magnetic resonance (NMR) spectroscopy over the pH range 3-13.5. The use of NMR allowed the direct observation of polytungstate anions in aqueous solution and at high concentration (0.5 mol L-1). Using this technique, the speciation of α-[SiW12O40]4-, α-[SiW11O39]8-, α-[NaSiW11O39]7-, α-[H2W12O40]6-, [H8W11O40]6-, [H7W11O40]7-, [W7O24]6-, [H2W12O42]10-, and WO42- was quantified as a function of pH. This work has allowed stability constants for α-[SiW12O40]4- (log K 46) and α-[SiW11O39]8- (log K 86) to be estimated.

Molecular-Structures and Conformations of 9,9'-Anthroin ('α' and 'β' Forms), 9,9'-Anthroin Acetate, and Some Related Benzoin Derivatives

The molecular conformations of 9,9′-anthroin (two forms, 'α' and 'β') and its acetate, as well as those of the acetates of benzoin and p- anisoin , have been studied by X-ray diffraction methods and found to display similar characteristics in respect of the COCO moiety. The conformation of 1,2-diaryl acyloins is characterized by a small torsion angle (10-24°) about the central four-atom fragment O=C-C-O, and the intramolecular distance between the two oxygen atoms does not exceed 2.8 Ǻ. The torsion angle about the three-bond segment Ar-C-C-Ar is in all cases smaller than 90°. In benzoin and its derivatives, the arylcarbonyl group deviates from planarity by 4-12°. In the cases of β 9,9′-anthroin and its acetate, the carbonyl group is twisted out of the plane of the anthracene moiety by 75°, and the two anthracene π-systems are in an overlapping arrangement; for α-anthroin, despite the presence of disorder in the COCOH moiety, a similar disposition can be inferred, indicative overall that, for such species, hydrogen bonding is not necessarily dominant in determining conformation.

(-)-Bukittinggine, the Major Alkaloid of Sapium baccatum: Crystal Structure and Absolute Configuration of Bukittinggine Hydrobromide

The structure and absolute configuration of (-)-bukittinggine (1), the major alkaloid isolated from the leaves of Sapium baccatum ( Roxb.) Ridley ( Euphorbiaceae ) have been determined from the crystal structure of its hydrobromide. Diffractometer data at 295 K were refined by least-squares techniques to a residual of 0.040 (3150 'observed' reflections). Crystals of bukittinggine hydrobromide are orthorhombic, P212121, a 14.947(4), b 14.580(4), c 8.801(2)Ǻ, Z4.

Color and Conformation of Some Derivatives of Benzil in the Solid-State: Crystal-Structures of 2,2′-Dimethoxy- 4,4′-Dimethoxy- , 4-4′Diethoxy- and 4,4'-Dibenzyloxy-benzil

The crystal structures of the colourless 2,2'-dimethoxybenzil (2) and 4,4'-diethoxybenzil (6), the yellow 4,4'-dimethoxybenzi (5), and the yellow polymorph of 4,4'-dibenzyloxybenzil (7) have been determined by single-crystal X-ray studies from diffractometer data at 295 K, and refined by full matrix least-squares techniques to residuals of 0.048 (1281 'observed' reflections), 0.041 (610), 0.052 (662) and 0.043 (2140) respectively. Crystals of 2,2′-dimethoxybenzil (2) are monoclinic, P21/c, a 7.861(4), b 7.991(2), c 21.557(9)�, β90.37(4)�, Z 4. Crystals of 4,4'-dimethoxybenzil (6) are monoclinic C2/c, a 21.912(9), b 4.055(2), c 15.197(5) �,β 102 13(3)� Z 4. Crystals of 4,4′-diethoxybenzil (6) are monoclinic C21/c, a 14.544(7), b 4.781(2), c 22.128(7), β 99.06(3)�, Z 4. Crystals of the yellow modification of 4,4'-dibenzyloxybenzil (7) are monoclinic P21/c, a 19.126(4), b 6.91 1(2), c 16.673(7) � β 99.52(3)�, Z 4. It has been found that there is a correlation between the colour of the crystal and the conformation adopted by the molecule in the solid state with the colourless derivatives of benzil having the aromatic ring planes orthogonal.

Conformational Studies of Some Piperazine-2,5-Diones: Crystal Structures of Three Isomeric Forms of Methylanhydropicroroccellin (Derivative of a Lichen Diketopiperazine) and a Derivative Bromohydrin

Single-crystal X-ray structure determinations have been carried out on three isomeric forms of the lichen diketopiperazine metabolite methylanhydropicroroccellin , C21H22N2O3, and a related bromohydrin , C20Hl9BrN2O3; all are based on a 6-benzyl-3-benzylidene-1,4- dimethylpiperazine-2,5-dione but differ in the substituents on the α and β carbons at position 6, enabling comparison of the resulting variation in conformation.

Differences in crystal properties and ligand affinities of an antifluorescyl Fab (4-4-20) in two solvent systems

An antigen-binding fragment (Fab) from a murine monoclonal antibody (4-4-20) with high affinity for fluorescein was cocrystallized with ligand in polyethylene glycol (PEG) and 2-methyl-2,4-pentanediol (MPD) in forms suitable for X-ray analyses. In MPD the affinity of the intact antibody for fluorescein was 300 times lower than the value (3.4 x 10(10) M-1) obtained in aqueous buffers. This decreased affinity was manifested by the partial release of bound fluorescein when MPD was added to solutions of liganded Fab during crystallization trials. In PEG, the ligand remained firmly bound to the protein. The liganded Fab crystallized in the monoclinic space group P2(1) in PEG, with a = 58.6, b = 97.2, c = 44.5 A and beta = 95.2 degrees. In MPD the space group was triclinic P1, with a = 58.3, b = 43.4, c = 42.3 A, alpha = 83.9 degrees, beta = 87.6 degrees, and gamma = 84.5 degrees. X-ray diffraction data were collected for both forms to 2.5-A resolution. Surprisingly, the triclinic form of the liganed antifluorescyl Fab had the same space group, closely similar cell dimensions, and practically the same orientation in the unit cell as an unliganded Fab (BV04-01) with activity against single-stranded DNA.

Selective O-Demethylation of 5,8-Dihydroxy-2,3-Dimethoxy-6-Methylnaphtho-1,4-Quinone: The Crystal Structures of 5,8-Dihydroxy-2,3-Dimethoxy-6-Methylnaphtho-1,4-Quinone and 2,5,8-Triacetoxy-3-Methoxy-6-Methylnaphtho-1,4-Quinone

It has been confirmed that treatment of 5,8-dihydroxy-2,3-dimethoxy-6-methylnaphtho-1,4- quinone (1) with dilute aqueous sodium hydroxide leads to selective O- demethylation. The hydrolysis product has been identified as 2,5,8-trihydroxy-3-methoxy-6-methylnaphtho1,4- quinone (3) from the crystal structure of the corresponding triacetate (4). The crystal structures of 5,8-dihydroxy-2,3-dimethoxy-6-methylnaphtho-1,4-quinone (1) and 2,5,8-triacetoxy-3-methoxy-6-methylnaphtho-1,4-quinone (4) were determined by X-ray diffraction; diffractometer data at 295 K were refined by least squares techniques to residuals of 0.074 (583 'observed' reflections) for (1) and 0.049 (2005) for (4). Crystals of (1) are monoclinic, P2l/c, a 3.873(4), b 20.21(1), c 15.OO(2) �, β 96.05(6)�, Z 4. Crystals of (4) are also monoclinic, P2l/c, a 10.532(5), b 14.596(6), c 12.097(6) �, β 109.74(4)�, Z 4.

Lewis-Base Adducts of Group-11 Metal(I) Compounds. XXX. 3:1 Complexes of Triphenylphosphine With Silver(I) Halides

3 : 1 adducts of triphenylphosphine, PPh3, with silver halides, AgX, have been characterized for chloride, bromide and iodide by single-crystal X-ray structure determinations, the chloride as its diacetone solvate. Crystals of the chloride, [(PPh3)3AgCl].2(CH3)2CO, are triclinic, P1, a 13.654(4), b 14.059(4), c 13.970(4) �, α 84.82(2), β 87.71(2), γ 75.68(2)�, Z 2; the structure was refined to a residual R of 0.061 for No = 2428 independent 'observed' reflections. Crystals of the bromide, [(PPh3)3AgBr], are trigonal, P3, a l9.366(6), c 10.787(6) �, Z 3, R was 0.054 for No = 2362. Crystals of the iodide, [(PPh3)3AgI], are monoclinic, P2l/n, a 18.993(8), b 13.807(4), c 17.781(8) �, β 96.11(4)�, Z 4; R was 0.042 for No = 3691. Ag-Cl, Br, I respectively are 2.533(4), 2.671(6)-2.691(4) and 2.858(1) �. Ag-P for each of the three structures respectively lie in the ranges 2.558(5)-2.582(4), 2.528(3)-2.549(7)and 2.544(2)-2.780(3) �.

The Crystal-Structures of (±)-(E)-2-(1-Amino-Ethylidene)-4,4,6-Trimethylcyclohexane-1,3-Dione [(±)-Aminoangustione] and (E)-2-(1-Aminoethylidene)-4,6,6-Trimethylcyclohex-4-Ene-1,3-Dione (Aminodehydroangustione)

The crystal structures of (�)-(E)-2-(1-aminoethylidene)-4,4,6- trimethylcyclohexane-1,3-dione [(�)- aminoangustione ] (8) and (E)-2-(1- aminoethylidene )-4,6,6-trimethylcyclohex-4-ene-1,3-dione ( aminodehydroangustione ) (9) have been determined by X-ray diffraction. Diffractometer data at 295 K were refined by full-matrix least-squares to residuals of 0.057 (712 'observed' reflections) for (8) and 0.061 (571) for (9). Crystals of (8) are tetragonal I 41/a, a 21.68(1), c 9.426(6)Ǻ, Z 16; crystals of (9) are orthorhombic Pmab , a 7.077(2), b 11.421(6), c 13.283(4)Ǻ, Z 4.

The Conformation of Some 1,1,2,2-Tetraacylethanes in the Solid-State: Crystal-Structures of 1,1,2,2-Tetrabenzoylethane, 1,2-Diacetyl-1,2-Dibenzoylethane and 1,1,2,2-Tetraethoxycarbonylethane

The crystal structures of 1,1,2,2-tetrabenzoylethane (3), 1,2-diacetyl- 1,2-dibenzoylethane (4) and 1,1,2,2-tetraethoxycarbonylethane (tetraethyl ethanetetracarboxylate ) (5) have been determined by X-ray diffraction from diffractometer data at 295 K and were refined by least-squares techniques to residuals of 0.050 (1077 'observed' reflections), 0.056 (3020) and 0.041 (480), respectively. Crystals of (3) are triclinic, Pī , Z 1, a 6.145(2), b 9.002(3), c 11.261(3) Ǻ; α 101.91(3), β 91.88(3), γ 105.94(3)°. Crystals of (4) are also triclinic, Pī , Z 2, a 17.119(5), b 7.210(1), c 7.175(2) Ǻ, α 89.59(2), β 72.92(2), γ 87.87(2)°. Crystals of (5) are tetragonal, P42/n, Z 4, a 17.748(6), c 5.515(1)Ǻ. In the solid state each compound exists in the keto form which adopts the antiperiplanar conformation about the central carbon-carbon bond.

Crystallographic Characterization of Isosevanine, a New Benzylisoquinoline Alkaloid

The characterization of a new benzylisoquinoline alkaloid, isosevanine, C18H15NO4, m.p. 148° isolated from Hedycarya angustifolia, by a single- crystal X-ray diffraction study is described. Crystals are monoclinic, P21/n, a 22.45(1), b 5.746(4), c 11.569(3) Ǻ, β 93.65(4)°, Z = 4; the structure was refined to a residual of 0.053 for 1016 independent 'observed' reflections.

The Molecular Geometry of Diastereoisomeric Bis[α-(9-anthryl)ethyl] Ethers

The crystal structures of racemic bis [α-(9-anthryl)] ether and its meso form have been determined by single-crystal X-ray diffraction methods at 295 K, being refined by least squares to residuals of 0.053 and 0.041 for 1868 and 3568 independent 'observed' reflections respectively. Crystals of the racemate are orthorhombic, Pcab, a 23.07(1), b 19.85(2), c 10.241(8) Ǻ, Z 8. Crystals of the meso form are triclinic, Pī , a 19.032(12), b 14.207(11), c 9.451(8) Ǻ, α 79.46(6), β 89.68(6), γ 68.97(5)°, Z 4. In the racemate , the dihedral angle between the methyl groups along the ether bonds is 12°, and the short axes of the anthracene moieties lie at an angle of about 120°. In the meso compound, for the two molecules the dihedral angles between the methyl groups along the ether bonds are 90 and 93°, the angle between the two anthracene moieties is 90°, and the interplanar angles between the partly overlapping aromatic systems are 46 and 43°.

The crystallographic characterization of an unusual chemical reversal of photoisomerization

lmines formed from pinacolone and primary amines could be acylated by acid chlorides or anhydrides to products hydrolysable to 1,3-diones. Renzoyl chloride with pinacolone benzylinline gave 3-(N-benzoyl-N-benzylamino)-4,4-dimethyl-1-phenylpent-2-en-1-one, both geometrical isomers of which were prepared. The yellow Z isomer was converted into the colourless E isomer on exposure to daylight and this change was reversed by brief treatment of the E isomer with aqueous ethanolic alkali. The Z and E isomers have been characterized crystallographically. The E isomer is monoclinic, C2/c, a 10.241(4), b 17.199(6), c 25.495(9) �, β 100.45(3)�, Z = 8; R was 0.052 for 1947 'observed' reflections. The Z-isomer is orthorhombic, P212121, a 18.24(1), b 15.60(l), c 7.871(4) �, Z = 4; R was 0.061 for 902 'observed' reflections.

Structural studies of polyhalogenated monoterpenes from Plocamium species

Extraction of Plocamium mertensii and an unclassified Plocamium species found off the Western Australian coast yielded (1R,2S,4S,1'E)-2-bromo-1-chloro-4-(2'-chloroethenyl)-1-methyl-5-methylenecyclohexane(3) and (1R,2S,4R,5R,1'E)-4-bromo-1,2-dichloro-5-(2'-chloroethenyl)-1,5-dimethylcyclohexane (4) respectively. The structures and absolute configurations were established by single-crystal X-ray crystallographic structure determination.

Constituents of Boesenbergia sp. Isolation and crystal structure of crotepoxide ([1R-(1α,2α,4α,5β,6α,7α,)]-4-[(Benzoyloxy)methyl]-3,8-dioxatricyclo[5, 1,0,02,4]octane-5,6-diyl diacetate)

The crystal structure of crotepoxide, isolated from the rhizomes of Boesenbergia sp., has been determined by single crystal X-ray diffraction methods at 295 K, being refined to a residual of 0.059 for 682 independent 'observed' reflections. Crystals are orthorhombic, P212121, a 23.53(2), b 10.59(1),c, 6.99(1)�, Z 4.

Molecular geometry of (E)- and (Z)-9-(β-Styryl)anthracenes

The molecular structures of (Z)-9-(8-styryl)anthracene, C22H16,(I),(E)-9-(P-styryl)anthracene, (2), and the photo-Diels-Alder dimer of 9-phenylethynylanthracene, C44H28, (3), containing a (Z)-9- (β-styryl) anthracene moiety of limited mobility have been determined by X-ray diffraction. Crystals of (1) are monoclinic, P21/c, a 5.507(4), b 13.050(7), c 21.425(10)�, β 95.73(5)�, Z 4; R was 0.047 for No 1604 independent 'observed' reflections. Crystals of (2) are monoclinic, P21/n, a 11.77(1), b 24.35(2), c 5.503(5) �, β 107.38(7)�, Z 4; R 0.050 for No 1100. Crystals of (3) are monoclinic, P21/c, a 10.719(7), b 18.627(8), c 15.509(8) �, β 101.10(5)�, Z 4; R 0.070 for No 1055. Increase in angle between the plane of the anthracene and the plane of the ethylenic double bond (78.4, 65.5, 81.9� respectively) is reflected in the electronic absorption spectra by an enhancement of the fine structure typical of the anthracene chromophore.

On the molecular conformation of (E)-1,2-Di(9-anthryl)ethene. X-ray structure analyses of the parent compound and its 10,10'-dibromo derivative

Two non-planar ground state conformations have been established by X-ray diffraction analyses of (E)-1,2-di(9-anthryl)ethene (1) and its 10,10'-dibromo derivative (2). The parent compound is characterized by a twofold axis of symmetry, the angle between the plane of the anthracene and that of the ethene being 55.1�. The angle between the two anthracene π-systems is 69.8�. The dibromo derivative (2) is characterized by a centre of symmetry, and the two anthracene π-systems are aligned parallel. The angle of twist between the plane of the anthracene and that of the ethene is 60.7�.

Studies of Australian soft corals. XXXII. The structure determination of degraded xenicin-type diterpenes from several Efflatounaria species

Three new diterpenes have been isolated from soft corals of the genus Efflatounaria (Coelenterata, Octocorallia, Alcyonacea, Xeniidae). The structure of the first compound (4) was elucidated on the basis of high-field 1H n.m.r. spectroscopy while that of the second metabolite (5) was determined by single-crystal X-ray analysis. The third diterpene (6) was structurally related to (5), and its structure was confirmed by chemical transformation. All three diterpenes can be derived from xenicin-type precursors, by cleavage and recyclization.

Crystal structure of aristoserratine

The crystal structure of the alkaloid aristoserratine,* C20H24N2O, has been determined by single-crystal X-ray diffraction methods at 295 K, the structure being refined to a residual of 0.034 for 1107 independent 'observed' reflections. Crystals are monoclinic, P21, a 14.836(5), b 8.568(3), c 6.633(3) �, β 98.05(3)�, Z 2. The relative configuration is established and, by inference, by comparison of the circular dichroism spectrum with that of aristoteline, the absolute configuration is assigned.

The chemistry of Eremophila spp. XIX. New cembrane diterpenes from E. granitica and E. abietina

The isolation and structural elucidation of five new cembrane diterpenes from two Eremophila species is reported. (1R,3S,4S,7E,11Z)-3,15-Epoxy-19-oxocembra-7,11-dien-18-oic acid (3) and (1R,3S,4S,7Z,11Z)-3,15-epoxycembra-7,11-dien-18-oic acid (7) were isolated from E. granitica, and dimethyl(1R,3S,4S,7E,11Z)-3,15-epoxycembra-7,11-diene-18,19-dioate (16), (1R,3S,4S,8R,11Z)-3,15-epoxycembr-11-ene-18,19-dioic acid (14) and its dimethyl ester were isolated from E. abietina. Structural studies on the diol derived from (14) were carried out by single-crystal X-ray diffraction analysis.

Crystal structure and absolute configuration of (+)-scandine hydrobromide

The major alkaloid of a Fijian Melodinus sp. (family Apocynaceae) has been identified as (+)-scandine (1). The crystal structure and absolute configuration of the acetone solvate of (+)-scandine hydrobromide have been determined by X-ray diffraction; diffractometer data at 295 K were refined by block diagonal least squares to a residual of 0.037 (2657 'observed' reflections). Crystals of the hydrobromide are monoclinic, P21, a 9.496(3), b 14.561(5), c 9.339(3) �, β 115.39(2)�, Z 2. Although the cations of (+)-scandine hydrobromide and (+)-N-methylmeloscine bromide have the same skeleton and the same absolute configuration, they have different conformations; this appears to be due to the steric effect of the N-methyl group in the latter cation.

The crystal structures of 1,3-Diphenylpropane-1,2,3-trione, 1,4-Diphenylbutane-1,2,3,4-tetraone, 2,4-Dihydroxy-2,5-diphenylfuran-3(2H)-one and 3,3-Dihydroxy- 1,4-diphenylbutane-1,2,4-trione

As a contribution towards a study of the relative disposition of adjacent carbonyl groups in polycarbonyl compounds, the crystal structures of 1,3-diphenylpropane-1,2,3-trione (1), 1,4-diphenyl- butane-1,2,3,4-tetraone (3), 2,4-dihydroxy-2,5-diphenylfuran-3(2H)-one (benzoylformoin) (7) and 3,3-dihydroxy-1,4-diphenylbutane-1,2,4-trio (8) have been determined by X-ray diffraction from diffractometer data at 295 K and refined by least-squares techniques to residuals of 0.036 (942 'observed' reflections), 0.029 (979), 0.067 (941) and 0.045 (1661), respectively. Crystals of 1,3-diphenylpropane-1,2,3-trione are triclinic, P1, a 9.756(4), b 8.813(3), c 8.303(3) �,α 68.56(2), β 67.53(3), γ 89.11(3)�, Z 2. Crystals of 1,4-diphenylbutane-1,2,3,4-tetraone are monoclinic P21/c, a 10.641(2), b 8.381(2), c 14.710(4) �, β 91.70(2)�, Z 4. 2,4-Dihydroxy-2,5- diphenylfuran-3(2H)-one also forms monoclinic crystals, P21/c, a 5.741(4), b 9.276(7), c 24.31(2) �, β 106.26(5)�, Z 4. Crystals of 3,3-dihydroxy-1,4-diphenylbutane-1,2,4-trine are triclinic, P1, a 13.08(1), b 12.43(1), c 8.895(8) �, α 82.54(8), β 81.87(7), γ 78.61(7)�, Z 4.

The crystal structure of 1α,4aβ,6β,9aα-Tetrahydroxy-4a,5aα,9a,10aβ-tetrahydrodibenzo[b,e][1,4]dioxin-2,7(1H,6H)-dione - A dimeric oxidation product of quinol

A single-crystal structure determination has revealed that the product obtained by oxidation of quinol with sodium chlorate and osmium tetroxide and crystallized from dimethyl sulfoxide is a solvate of 1α,4aβ,6β,9aα-tetrahydroxy-4a,5aα,9a,10aβ-tetrahydrodibenzo[b,e][1,4]dioxin-2,7(1H,6H)-dione. The crystals of C12H12O8,2(CH3)2SO are monoclinic, P21/n, a 7.859(5), b 9.774(7), c 13.14(1) Ǻ, β 93.08(6)°, Z 2, with each molecule of the dione centred on a crystallographic centre of symmetry. The solvent molecules are disordered. The structure was refined by least squares to a residual of 0.046 for 1361 'observed' reflections.

Chemistry and crystal structures of tetrabenzoylethylene, its photolysis product and tetraacetylethylene

X-ray crystallographic analysis has revealed that the light-sensitive form (A) and the light-stable form (A') of tetrabenzoylethylene are not valence tautomers but are two crystalline modifications of the same substance. The difference in the stability of these forms to light appears to be a consequence of their different molecular conformations and packing in the solid state. The molecular conformation of the A form is represented by (8) and that of the A' form by (9). The related tetraacetylethylene has the conformation (10) in the solid state. X-ray crystallographic analysis has also revealed that the photolysis product (B) of tetrabenzoylethylene is 4-phenoxy-3,4,6-triphenyl-1H,4H-furo[3,4-c]-furan-1-one (11). ��� The crystal structures of (8), (9), (10) and (11) were determined by X-ray diffraction: diffractometer data at 295 K were refined by least-squares techniques to residuals of 0.064 (2161 'observed' reflections) for (8), 0.057 (1310) for (9), 0.049 (1295) for (10) and 0.061 (1639) for (11). Crystals of (8) are monoclinic, P21/n, a 8.775(5), b 17.352(9), c 30.985(8)Ǻ, β 93.01(3)°, Z 8. Crystals of (9) which contain carbon disulfide are monoclinic, A2/a, a 21.21(2), b 6.181(4), c 20.35(2) Ǻ, β 102.77(7)°, Z 4. Crystals of (10) are monoclinic, P21/n, a 7.540(2), b 4.392(2), c 14.770(4) Ǻ, β 96.29(2)°, Z 2. Crystals of (11) are monoclinic, P1/n, a 14.820(4), b 15.000(3), c 10.819(4)Ǻ, β 106.02(2)°, Z 4.