1,4-dicyanobenzene as a scaffold for the preparation of bimetallic actinide complexes exhibiting metal-metal communication

Reaction of two equivalents of [(C(5)Me(4)Et)(2)U(CH(3))(Cl)] (6) or [(C(5)Me(5))(2)Th(CH(3))(Br)] (7) with 1,4-dicyanobenzene leads to the formation of the novel 1,4-phenylenediketimide-bridged bimetallic organoactinide complexes [{(C(5)Me(4)Et)(2)(Cl)U}(2)(mu-{N==C(CH(3))-C(6)H(4)-(CH(3))C==N})] (8) and [{(C(5)Me(5))(2)(Br)Th}(2)(mu-{N==C(CH(3))-C(6)H(4)- (CH(3))C==N})] (9), respectively. These complexes were structurally characterized by single-crystal X-ray diffraction and NMR spectroscopy. Metal-metal interactions in these isovalent bimetallic systems were assessed by means of cyclic voltammetry, UV-visible/NIR absorption spectroscopy, and variable-temperature magnetic susceptibility. Although evidence for magnetic coupling between metal centers in the bimetallic U(IV)/U(IV) (5f(2)-5f(2)) complex is ambiguous, the complex displays appreciable electronic communication between the metal centers through the pi system of the dianionic diketimide bridging ligand, as judged by voltammetry. The transition intensities of the f-f bands for the bimetallic U(IV)/U(IV) system decrease substantially compared to the related monometallic ketimide chloride complex, [(C(5)Me(5))(2)U(Cl){-N==C(CH(3))-(3,4,5-F(3)-C(6)H(2))}] (11). Also reported herein are new synthetic routes to the actinide starting materials [(C(5)Me(4)Et)(2)U(CH(3))(Cl)] (6) and [(C(5)Me(5))(2)Th(CH(3))(Br)] (7) in addition to the syntheses and structures of the monometallic uranium complexes [(C(5)Me(4)Et)(2)UCl(2)] (3), [(C(5)Me(4)Et)(2)U(CH(3))(2)] (4), [(C(5)Me(4)Et)(2)U{-N==C(CH(3))-C(6)H(4)-C==N}(2)] (10), and 11.     

Modeling oil droplets in plateau borders

It is widely known that oil droplets can decrease the stability of aqueous films and foams. While less widely recognized, it has also been observed that oil droplets can, under certain circumstances, increase the stability of foams, especially if they are caught in the Plateau borders. In this paper, how the oil droplet deforms and is, in turn, deformed by the Plateau border is modeled using Surface Evolver. The two dimensionless parameters that affect these shapes are the size of the oil droplet relative to the Plateau border and the ratio of the oil-water interfacial tension to the air-water interfacial tension. The calculated pressures in all the phases were used to obtain the pressure exerted on the oil-water-air pseudoemulsion film, which allows the factors that influence the stability of these droplets in the Plateau border to be investigated. The final section of the paper demonstrates that the presence of an oil droplet in a Plateau border can have a major influence on the drainage of the aqueous phase along the Plateau border. This retardation of the flow would result in the oil droplets in the Plateau borders increasing the stability of foams in which they are found.     

Nucleic acid related compounds. 116. Nonaqueous diazotization of aminopurine nucleosides. Mechanistic considerations and efficient procedures with tert-butyl nitrite or sodium nitrite

Nonaqueous diazotization-dediazoniation of two types of aminopurine nucleoside derivatives has been investigated. Treatment of 9-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-2-amino-6-chloropurine (1) with SbCl(3)/CH(2)Cl(2) was examined with benzyltriethylammonium (BTEA) chloride as a soluble halide source and tert-butyl nitrite (TBN) or sodium nitrite as the diazotization reagent. Optimized yields (>80%) of the 2,6-dichloropurine derivative were obtained with SbCl(3). Combinations with SbBr(3)/CH(2)Br(2) gave the 2-bromo-6-chloropurine product (>60%), and SbI(3)/CH(2)I(2)/THF gave the 2-iodo-6-chloropurine derivative (>45%). Antimony trihalide catalysis was highly beneficial. Mixed combinations (SbX(3)/CH(2)X'(2); X/X' = Br/Cl) gave mixtures of 2-(bromo, chloro, and hydro)-6-chloropurine derivatives that were dependent on reaction conditions. Addition of iodoacetic acid (IAA) resulted in diversion of purine radical species into a 2-iodo-6-chloropurine derivative with commensurate loss of other radical-derived products. This allowed evaluation of the efficiency of SbX(3)-promoted cation-derived dediazoniations relative to radical-derived reactions. Efficient conversions of adenosine, 2'-deoxyadenosine, and related adenine nucleosides into 6-halopurine derivatives of current interest were developed with analogous combinations.     

Stereodefined synthesis of O3'-labeled uracil nucleosides. 3'-[(17)O]-2'-Azido-2'-deoxyuridine 5'-diphosphate as a probe for the mechanism of inactivation of ribonucleotide reductases

Thermolysis of a 2'-[(16)O]-O-benzoyl-[(17)O]-5'-O-(tert-butyldimethylsilyl)-O(2),3'-cyclouridine derivative gave the more stable 3'-[(17)O]-O-benzoyl-[(16)O]- 5'-O-(tert-butyldimethylsilyl)-O(2),2'-cyclouridine isomer, which was converted into 3'-[(17)O]-2'-azido-2'-deoxyuridine by deprotection and nucleophilic ring opening at C2' with lithium azide. The 5'-diphosphate was prepared by nucleophilic displacement of the 5'-O-tosyl group with tris(tetrabutylammonium) hydrogen pyrophosphate. Model reactions gave (16)O and (18)O isotopomers, and base-promoted hydrolysis of an O(2),2'-cyclonucleoside gave stereodefined access to 3'-[(18)O]-1-(beta-D-arabinofuranosyl)uracil. Inactivation of ribonucleoside diphosphate reductase with 2'-azido-2'-deoxynucleotides results in appearance of EPR signals for a nitrogen-centered radical derived from azide, and 3'-[(17)O]-2'-azido-2'-deoxyuridine 5'-diphosphate provides an isotopomer to perturb EPR spectra in a predictable manner.     

Amine-functionalised SBA-15 of tailored pore size for heavy metal adsorption

This study examines the synthesis of SBA-15 with tailored pore sizes through controlled thermal treatment for the adsorption of Pb and Cd ions. The aim is to produce a material that can adsorb heavy metals at both high and low concentrations. The materials were characterised by means of N(2) physisorption, powder X-ray diffraction (PXRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), microanalysis and transmission electron microscopy (TEM). The surface areas ranged from 410 to 871 m(2)g(-1), and pore diameter was increased from 5.9 to 10.8 nm. This method allows for maximum adsorption of metal ions at very low concentrations. Metal ion adsorption was determined using an Atomic Absorption Spectrophotometer. The effects of pH were found to play a major role in the precipitation and, therefore, adsorption of metal ions. This method proved to be efficient at adsorbing large quantities of both metals (39 and 41 mg g(-1) for Pb and Cd, respectively).     

Dithiolene transfer from nickel to a dimolybdenum centre: the first dithiolene alkyne complex

Transfer of dithiolene ligands from [Ni(S₂C₂Ph₂)₂] to the dimolybdenum complex [Mo₂(μ-C₂R₂)(CO)₄Cp₂] (R=CO₂Me, Cp=η-C₅H₅) affords the first example of a dithiolene alkyne complex, [Mo₂(μ-C₂R₂)(μ-S₂C₂Ph₂)₂Cp₂], together with [Mo₂(μ-SCRCR)(μ-SCPhCPh)Cp₂] in which sulfur transfer from dithiolene to alkyne has occurred.     

内蒙古地区天然植物沙棘果中黄色素的提取工艺及性质研究

以内蒙古地区沙棘果实为原料，研究了提取黄色素的工艺条件，同时对该色素的性质进行了初步探讨。结果表明，以95％的乙醇溶液作浸提剂，提取的黄色素浓度最高，工艺流程简单易行，且无毒，无污染。对提取的黄色素进行的性质试验表明，沙棘黄色素对光、热具有较好的稳定性，适用于酸性或弱碱性的食品中，葡萄糖、氧化剂(H2O2)、还原剂(Na2SO3)等食品添加剂均无明显影响以上结果为这种优良天然色素的开发与应用提供了参考。     

Extending the Family of V4+ S=${{ 1/2 }}$ Kagome Antiferromagnets

The ionothermal synthesis, structure, and magnetic susceptibility of a novel inorganic–organic hybrid material, imidazolium vanadium(III,IV) oxyfluoride [C₃H₅N₂][V₉O₆F₂₄(H₂O)₂] (ImVOF) are presented. The structure consists of inorganic vanadium oxyfluoride slabs with kagome layers of V⁴⁺ S=${{ 1/2 }}$ ions separated by a mixed valence layer. These inorganic slabs are intercalated with imidazolium cations. Quinuclidinium (Q) and pyrazinium (Pyz) cations can also be incorporated into the hybrid structure type to give QVOF and PyzVOF analogues, respectively. The highly frustrated topology of the inorganic slabs, along with the quantum nature of the magnetism associated with V⁴⁺, means that these materials are excellent candidates to host exotic magnetic ground states, such as the highly sought quantum spin liquid. Magnetic susceptibility measurements of all samples suggest an absence of conventional long‐range magnetic order down to 2 K despite considerable antiferromagnetic exchange.     

Surface‐Specific Functionalization of Nanoscale Metal–Organic Frameworks

A method for modifying the external surfaces of a series of nanoscale metal–organic frameworks (MOFs) with 1,2‐dioleoyl‐sn‐glycero‐3‐phosphate (DOPA) is presented. A series of zirconium‐based nanoMOFs of the same topology (UiO‐66, UiO‐67, and BUT‐30) were synthesized, isolated as aggregates, and then conjugated with DOPA to create stably dispersed colloids. BET surface area analysis revealed that these structures maintain their porosity after surface functionalization, providing evidence that DOPA functionalization only occurs on the external surface. Additionally, dye‐labeled ligand loading studies revealed that the density of DOPA on the surface of the nanoscale MOF correlates to the density of metal nodes on the surface of each MOF. Importantly, the surface modification strategy described will allow for the general and divergent synthesis and study of a wide variety of nanoscale MOFs as stable colloidal materials.