J. Appl. Cryst.の発刊に際して

Metal-Organic Derivatives with Fluorinated Ligands as Precursors for Inorganic Nanomaterials.

RifDH10, the dehydratase domain from the terminal module of the rifamycin polyketide synthase, catalyzes the stereospecific syn dehydration of the model substrate (2S,3S)-2-methyl-3-hydroxypentanoyl-RifACP10, resulting in the exclusive formation of (E)-2-methyl-2-pentenoyl-RifACP10 RifDH10 does not dehydrate any of the other three diastereomeric, RifACP10-bound, diketide thioester substrates On the other hand, when EryACP6, from the sixth module of the erythromycin polyketide synthase, is substituted for RifACP10, RifDH10 stereospecifically dehydrates only (2R,3R)-2-methyl-3-hydroxypentanoyl-EryACP6 to give exclusively (E)-2-methyl-2-pentenoyl-EryACP6, with no detectable dehydration of any of the other three diastereomeric, EryACP6-bound, diketides An identical alteration in substrate diastereospecificity was observed for the corresponding N-acetylcysteamine or pantetheine thioester analogues, regardless of acyl chain length or substitution pattern Incubation of (2RS)-2-methyl-3-ketopentanoyl-RifACP10

Structure and Stereospecificity of the Dehydratase Domain from the Terminal Module of the Rifamycin Polyketide Synthase

A series of modified, hafnium tert-butoxide ([Hf(OBut)4]) compounds (1–26) were crystallographically characterized, and representative species were then used to produce HfO2nanoparticles. This systematically varied family of [Hf(OR)4] compounds was developed from the reaction of [Hf(OBut)4] with a series of (i) Lewis basic solvents, tetrahydrofuran, pyridine, or 1-methylimidazole; (ii) simple phenols, HOC6H4(R)-2 or HOC6H3(R)2-2,6 where R = CH3, CH(CH3)2, or C(CH3)3; and (iii) complex polydentate alcohols, tetrahydrofuran methanol (H-OTHF), pyridinecarbinol (H-OPy), and tris(hydroxymethylethane) (THME-H3). The solvent-modified products were crystallographically characterized as [Hf(OBut)4(solv)n] (1–3). The phenoxide (OAr)-exchanged [Hf(OBut)4] products isolated from toluene were characterized as dimeric [Hf(OAr)n(OBut)4–n]2 (4 and 5) or [Hf(μ-OH)(OAr)3(HOBut)]2 (6 and 7) for the less sterically demanding OAr ligands and [Hf(OAr)n(OBut)4–n(HOBut)] (8 and 9) monomers for the larger OAr ligands. When Lewis ...

Synthesis and structural characterization of a family of modified hafnium tert-butoxide for use as precursors to hafnia nanoparticles.

Thrombin exists as an ensemble of active (E) and inactive (E*) conformations that differ in their accessibility to the active site. Here we show that redistribution of the E*-E equilibrium can be achieved by perturbing the electrostatic properties of the enzyme. Removal of the negative charge of the catalytic Asp102 or Asp189 in the primary specificity site destabilizes the E form and causes a shift in the 215-217 segment that compromises substrate entrance. Solution studies and existing structures of D102N document stabilization of the E* form. A new high-resolution structure of D189A also reveals the mutant in the collapsed E* form. These findings establish a new paradigm for the control of the E*-E equilibrium in the trypsin fold.

/pdf/loop-electrostatics-asymmetry-modulates-the-preexisting-24gljji4wk.pdf

Loop Electrostatics Asymmetry Modulates the Preexisting Conformational Equilibrium in Thrombin

The binuclear title compound, [Hf2(C5HF6O2)6(OH)2]·C3H6O, contains an HfIV atom which is eight coordinated and surrounded by three chelating β-diketonato 1,1,1,5,5,5-hexa­fluoro­acetyl­acetonate (hfaa) ligands and two bridging OH groups situated on a twofold rotation axis. The HfO8 coordination polyhedron shows a slightly distorted Archimedean square anti-prismatic coordination with average Hf—O, C—O, C—CMe distances of 2.19 (2), 1.26 (2) and 1.49 (2) A, respectively, and an O—Hf—O bite angle of 75.3 (5)°. Weak O—H⋯O hydrogen bonding inter­actions are observed between one of the bridging hydr­oxy groups and the disordered solvent mol­ecule.

Di-μ-hydroxido-bis[tris(1,1,1,5,5,5-hexa­fluoro­acetyl­acetonato-κ2O,O′)hafnium(IV)] acetone solvate

In the title compound, [Hf(C9H6NO)4]·2C7H8, the hafnium metal centre is coordinated by four N,O-donating bidentate quinolin-8-olate ligands arranged to give a square-anti­prismatic coordination polyhedron with a slightly distorted dodeca­hedral geometry. The average Hf—O and Hf—N distances are 2.096 (3) and 2.398 (3) A, respectively, and the average O—Hf—N bite angle is 70.99 (11)°. The crystal packing is controlled by π–π inter­actions between quinoline ligands of neighbouring mol­ecules and hydrogen-bonding inter­actions. The inter­planar distances vary between 3.138 (1) and 3.208 (2) A, while the centroid–centroid distances range from 3.576 (1) to 4.074 (1) A.

https://journals.iucr.org/e/issues/2009/12/00/bg2301/bg2301.pdf

Tetra­kis(quinolin-8-olato-κ2N,O)hafnium(IV) toluene disolvate

In the title compound, [Hf(C15H11O2)4], the HfIV atom is coordinated by four 1,3-diphenyl­propane-1,3-dionato ligands with an average Hf—O distance of 2.17 (3) A and O—Hf—O bite angles varying from 74.5 (1) to 75.02 (9)°. The coordination polyhedron shows a slightly distorted Archimedean square-anti­prismatic geometry. The crystal packing is stabilized by weak C—H⋯O inter­actions.

https://journals.iucr.org/e/issues/2010/09/00/bg2349/bg2349.pdf

Tetra­kis(1,3-diphenyl­propane-1,3-dionato)hafnium(IV)

C701 The high crystal quality of the as-grown crystals as well as the efficiency of the substitution was pointed out by room-temperature single-crystal X-Ray Diffraction (XRD) data. The evolution of the structural distortion with the rise of substitution rate from ambient temperature to high temperature (near 1050°C) was followed by powder X-Ray Diffraction and Raman scattering analyses. Both electrical and optical twins were refined using Shelxl 97 software. The substitution rate and its distribution homogeneity along different crystal were carefully examined by Energy Dispersive X-ray analyses.

/pdf/crystallographic-and-kinetic-study-of-octa-coordinated-84xx9rljfw.pdf

Crystallographic and kinetic study of octa-coordinated hafnium(IV) complexes

In the title compound, [Hf(C11H10NO)4]·2C3H7NO, the HfIV atom is coordinated by four N,O-donating bidentate 5,7-dimethyl-8-quinolino­late (Ox−) ligands arranged to give a distorted square-anti­prismatic coordination polyhedron. The average Hf—O and Hf—N distances are 2.098 and 2.298 A, respectively, and the average O—Hf—N bite angle is 70.2°. The crystal packing is controlled by π–π inter­actions between Ox− ligands of neighbouring mol­ecules, giving rise to a three-dimensional supra­molecular grid network. The inter­planar distances vary from 3.441 (1) to 3.509 (1) A, while the centroid–centroid distances vary from 3.688 (2) to 3.759 (12) A. A non-classical C—H⋯O hydrogen bond is observed between the complex and one of the solvate mol­ecules.

https://journals.iucr.org/e/issues/2011/10/00/wm2534/wm2534.pdf

J.A. Viljoen

Papers

Di-μ-hydroxido-bis[tris(1,1,1,5,5,5-hexafluoroacetylacetonato-κ2O,O′)hafnium(IV)] acetone solvate

Tetrakis(quinolin-8-olato-κ2N,O)hafnium(IV) toluene disolvate

Tetrakis(1,3-diphenylpropane-1,3-dionato)hafnium(IV)

Crystallographic and kinetic study of octa-coordinated hafnium(IV) complexes

Tetra-kis(5,7-dimethyl-quinolin-8-olato-κN,O)hafnium(IV) dimethyl-formamide disolvate.

J.A. Viljoen

Papers

Di-μ-hydroxido-bis[tris(1,1,1,5,5,5-hexa­fluoro­acetyl­acetonato-κ2O,O′)hafnium(IV)] acetone solvate

Tetra­kis(quinolin-8-olato-κ2N,O)hafnium(IV) toluene disolvate

Tetra­kis(1,3-diphenyl­propane-1,3-dionato)hafnium(IV)

Crystallographic and kinetic study of octa-coordinated hafnium(IV) complexes

Tetra-kis(5,7-dimethyl-quinolin-8-olato-κN,O)hafnium(IV) dimethyl-formamide disolvate.

Di-μ-hydroxido-bis[tris(1,1,1,5,5,5-hexafluoroacetylacetonato-κ2O,O′)hafnium(IV)] acetone solvate

Tetrakis(quinolin-8-olato-κ2N,O)hafnium(IV) toluene disolvate

Tetrakis(1,3-diphenylpropane-1,3-dionato)hafnium(IV)