Tuning Properties of Iron Oxide Nanoparticles in Aqueous Synthesis without Ligands to Improve MRI Relaxivity and SAR.

Aqueous synthesis without ligands of iron oxide nanoparticles (IONPs) with exceptional properties still remains an open issue, because of the challenge to control simultaneously numerous properties of the IONPs in these rigorous settings. To solve this, it is necessary to correlate the synthesis process with their properties, but this correlation is until now not well understood. Here, we study and correlate the structure, crystallinity, morphology, as well as magnetic, relaxometric and heating properties of IONPs obtained for different durations of the hydrothermal treatment that correspond to the different growth stages of IONPs upon initial co-precipitation in aqueous environment without ligands.

{2,2'-[1,1'-(3-Aza-pentane-1,5-diyl-dinitrilo)diethyl-idyne]diphenolato}(piperidine)cobalt(III) tetra-phenyl-borate.

The title compound, [Co(C(20)H(23)N(3)O(2))(C(5)H(11)N)](C(24)H(20)B) or [Co{(Me-sal)(2)dien}(pprdn)]BPh(4), where (Me-sal)(2)dien is 2,2'-[1,1'-(3-aza-pentane-1,5-diyldinitrilo)diethyl-idyne]diphenolate and pprdn is piperidine, contains a penta-dentate (Me-sal)(2)dien ligand furnishing an N(3)O(2) set, such that two of the N and one of the O atoms of the salicyl-idene rings define three positions of an equatorial plane, whereas the secondary amine N atom and the other O atom of the salicyl-idene lie in axial positions. The piperidine ligand occupies an equatorial position trans to one of the imine N atoms of the salicyl-idene. In the observed conformation of the penta-dentate ligand, the salicyl-idene rings attain asymmetrical positions owing to the structural demands.

Potassium gallium hydrogenphosphate fluoride, K(2)Ga[H(HPO(4))(2)]F(2).

Hydrothermally synthesized dipotassium gallium {hydrogen bis[hydrogenphosphate(V)]} difluoride, K(2)Ga[H(HPO(4))(2)]F(2), is isotypic with K(2)Fe[H(HPO(4))(2)]F(2). The main features of the structure are ([Ga{H(HPO(4))(2)}F(2)](2-))(n) columns consisting of centrosymmetric Ga(F(2)O(4)) octahedra [average Ga-O = 1.966 (3) Angstrom and Ga-F = 1.

Electrochemically triggered open and closed Pacman bis-metalloporphyrins.

A new type of very compact Pacman bis-porphyrin scaffold has been obtained in which a calix[4]arene spacer provides both cofacial preorganization and flexibility. Changes in the distance between the two tetrapyrrolic macrocycles can be triggered by electrochemistry, where closed and open conformers can be interconverted in a handclapping motion.

{2,2'-[1,1'-(4-Azaheptane-1,7-diyldinitrilo)diethylidyne]diphenolato}copper(II).

The quinquedentate ligand 2,2'-[1,1'-(4-azaheptane-1,7-diyldinitrilo)diethylidyne]diphenol in the title compound, [Cu(C22H27N3O2)], furnishes an N3O2 donor set, which results in a distorted square-pyramidal coordination; the two O and two imine N atoms lie in the basal plane, while the secondary amine N atom of the ligand occupies the axial position. The axial Cu-N bond is 0.33 A longer than the average of the equatorial bonds, and the O atoms are trans.

Structural and binding features of cofacial bis-porphyrins with calixarene spacers: pac-man porphyrins that can chew.

Based on the efficient combination of calixarene spacers and acetylenic porphyrin derivatives, a new generation of cofacial bis-porphyrins has been synthesized. The first crystal structure of a cofacial bis-porphyrin-calixarene conjugate is reported. Their unique architectural features, analogous to those of pac-man-type bis-porphyrins, allow these calixarene-porphyrin conjugates to adapt their shape to the size of bidentate guests, such as diazabicyclo[2.

3-[2,6-Bis(diethylcarbamoyl)pyridin-4-yl]-N-(tert-butoxycarbonyl)alanine methyl ester: a chiral tridentate ligand that causes a diastereomeric excess of its lanthanide complexes in solution.

L(4), or 3-[2,6-bis(diethylcarbamoyl)pyridin-4-yl]-N-(tert-butoxycarbonyl)alanine methyl ester, C(24)H(38)N(4)O(6), crystallizes in neat [010] laths stabilized by abundant intra- and intermolecular hydrogen bonds. The strongest of these form [010] chains of molecules, thus rationalizing the fastest growth direction, while the slowest direction coincides with the normal to the (110) layers, which are linked by very weak hydrogen bonds. There exist two independent molecules, the distances and bond angles of which differ in a random manner only.

Taxiphyllin from Henriettella fascicularis.

(2R)-alpha-(beta-D-Glucopyranosyloxy)-4-hydroxybenzeneacetonitrile (taxiphyllin) dihydrate, C(14)H(17)NO(7) x 2H(2)O, is a naturally occurring cyanogenetic glycoside which has been isolated from Henriettella fascicularis (Sw.) C. Wright (Melastomataceae).

Urotropin azelate: a rather unwilling co-crystal.

Urotropin (U) and azelaic acid (AA) form 1:1 co-crystals (UA) that give rise to a rather complex diffraction pattern, the main features of which are diffuse rods and bands in addition to the Bragg reflections. UA is characterized by solvent inclusions, parasite phases, and high vacancy and dislocation densities. These defects compounded with the pronounced tendency of U to escape from the crystal edifice lead to at least seven exotic phase transitions (many of which barely manifest themselves in a differential scanning calorimetry trace).

Stability and Size-Discriminating Effects in Mononuclear Lanthanide Triple-Helical Building Blocks with Tridentate Aromatic Ligands.

The planar aromatic tridentate ligand 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (L(1)) reacts with Ln(III) (Ln = La-Lu) in acetonitrile to give the successive complexes [Ln(L(1))(n)()](3+) (n = 1-3). Stability constants determined by spectrophotometry and potentiometric competitive titrations with Ag(I) show that the 1:1 and the 1:2 complexes display the usual thermodynamic behavior associated with electrostatic effects while the 1:3 complexes exhibit an unusual selectivity for the midrange Ln(III) ions (Delta log K(3)(Gd-Lu) approximately 4). A detailed investigation of the solution structure of [Ln(L(1))(3)](3+) (Ln = La-Dy) reveals that the closely packed triple-helical structure found in the crystal structure of [Eu(L(1))(3)](3+) is retained in acetonitrile for the complete series.

Luminescent Properties of Lanthanide Nitrato Complexes with Substituted Bis(benzimidazolyl)pyridines.

The protonated form of the ligand 2,6-bis(1'-methylbenzimidazol-2'-yl)pyridine crystallizes as its perchlorate salt (HL(1))ClO(4) (1) in the orthorhombic system Pbca, with a = 13.976(3) Å, b = 14.423(3) Å, c = 19.