Occurrence and prevention of photodissolution at the phase junction of magnetite and titanium dioxide

A stable magnetic photocatalyst was prepared by coating a magnetic core with a layer of photoactive titanium dioxide. A direct deposition of titanium dioxide onto the surface of magnetic iron oxide particles proved ineffective in producing a stable magnetic photocatalyst, with high levels of photodissolution being observed with these samples. This observed photodissolution is believed to be due to the dissolution of the iron oxide phase, induced by the photoactive the titanium dioxide layer due to electronic interactions at the phase junction in these magnetic photocatalysts. The introduction of an intermediate passive SiO₂ layer between the titanium dioxide phase and the iron oxide phase inhibited the direct electrical contact and hence prevented the photodissolution of the iron oxide phase. The magnetic photocatalyst is for use in slurry-type reactors from which the catalyst can be easily recovered by the application of an external magnetic field.     

Aminolysis of methoxy groups in pyrimidine derivatives. Activation by 5‐nitroso

The nucleophilic substitution of 2‐mefhoxy groups in pyrimidine derivatives was strongly activated by introduction of a 5‐nitroso group on to the pyrimidine ring. The aminolysis of several 2‐methoxy‐5‐nitrosopyrimidine derivatives was performed at room temperature in hydroxylic as well as in non‐hydroxylic media with different primary amines in short time and good yields. The aminolysed substrates include 6‐[(per‐O‐acetyl)glycosyl]aminopyrimidines which afforded the corresponding 2‐aminopyrimidines without harming the acetyl protecting groups of the sugar moiety.     

A quasi‐diamondoid hydrogen‐bonded framework in an­hydro­us sulfanilic acid

The title compound (C₆H₇NO₃S) exists as a zwitterion (4‐ammonio­benzene­sulfonate), ⁺H₃NC₆H₄SO₃^?, and these units are linked into a three‐dimensional framework by two distinct two‐centre N—H?O hydrogen bonds [H?O 1.84 and 1.87 Å; N?O 2.767 (2) and 2.746 (2) Å; N—H?O 166 and 172°] and a planar three‐centre N—H?(O)₂ hydrogen bond [H?O 2.03 and 2.37 Å; N?O 2.816 (2) and 2.877 (2) Å; N—H?O 162 and 111°; O?H?O 86°].     

Hydrogen‐bonded molecular ladders in S‐(4‐nitrophenyl)thioglycolic acid

Molecules of the title compound, [(4‐nitro­phenyl)­sulfanyl]­acetic acid, C₈H₇NO₄S, are linked by paired O—H?O hydrogen bonds [H?O 1.81 Å, O?O 2.6456 (15) Å and O—H?O 178°] into centrosymmetric dimers containing an R(8) motif. A single C—H?O hydrogen bond having a nitro O atom as acceptor [H?O 2.47 Å, 3.3018 (19) Å and C—H?O 147°] links the dimers into a molecular ladder, and neighbouring ladders are weakly linked into sheets by aromatic π–π‐stacking interactions.     

Evaluation of protein-A chromatography media

In process-scale antibody purification, protein-A affinity chromatography is commonly used as the initial purification step. In this paper, two different protein-A media were evaluated. These adsorbents have a porous glass backbone with different pore sizes: 700 A and 1000 A. Adsorption equilibrium data of human immunoglobulins on these media were measured via a batch technique and correlated using the Langmuir isotherm model. A larger static capacity was found for the smaller pore size material, which is probably a result of the larger specific surface area and associated higher ligand concentration. The protein uptake kinetics were also obtained via a stirred tank experiment using different initial protein concentrations. A surface layer model was used to represent the protein uptake by the media and to estimate values of a concentration-independent effective diffusivity within the particle. Experimental breakthrough curves were also obtained from packed beds operated under different conditions. Calculated breakthrough profiles were found to be in good agreement with the experimental results. Experimental breakthrough data were used to determine the dependence of the dynamic capacity of the media as a function of the fluid residence time. A larger dynamic capacity was also found for the smaller pore size media. The permeability of large scale packed beds was also reported and used in conjunction with the dynamic capacity to calculate the process production rate.     

Redetermination of 6‐amino‐5‐formyl‐1,3‐dimethyluracil monohydrate at 120 K: a polarized molecular structure and two interwoven hydrogen‐bonded frameworks

The title compound [systematic name: 6‐amino‐5‐formyl‐1,3‐dimethylpyrimidine‐2,4(1H,3H)‐dione monohydrate], C₇H₉N₃O₃·H₂O, has been reexamined at 120 K. The improved precision of the intramolecular dimensions provides evidence for a polarized molecular–electronic structure, and the molecular components are linked by one N—H...O and two O—H...O hydrogen bonds into two interwoven three‐dimensional frameworks, which are weakly linked by the longer component of a three‐centre N—H...(O)₂ hydrogen bond.     

Photochemistry of the pi-extended 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene system: generation and characterisation of the radical cation, dication, and derived products

Flash photolysis of bis[4.5-di(methylsulfanyl) 1,3-dithiol-2-ylidene]-9,10(-dihydroanthracene (1) in chloroform leads to formation of the transient radical cation species 1.+ which has a diagnostic broad absorption band at lambdamax approximately 650 nm. This band decays to half its original intensity over a period of about 80 micros. Species 1.+ has also been characterised by resonance Raman spectroscopy. In degassed solution 1.+ disproportionates to give the dication 1(2+), whereas in aerated solutions the photodegradation product is the 10-[4,5-di(methylsulfanyl) 1,3-dithiol-2-ylidene]anthracene-9(10 H)one (2). The dication 1(2+) has been characterised by a spectroelectrochemical study [lambdamax (CH2Cl2) = 377, 392, 419, 479 nm] and by an X-ray crystal structure of the salt 1(2-) (ClO4)2, which was obtained by electrocrystallisation. The planar anthracene and 1,3-dithiolium rings in the dication form a dihedral angle of 77.2 degrees; this conformation is strikingly different from the saddle-shaped structure of neutral 1 reported previously.     

2,6‐Diiodo‐4‐nitrophenol, 2,6‐diiodo‐4‐nitrophenyl acetate and 2,6‐diiodo‐4‐nitroanisole: interplay of hydrogen bonds,iodo–nitro interactions and aromatic π–π‐stacking interactions to give supramolecular structures in one,two and three dimensions

In 2,6‐di­iodo‐4‐nitro­phenol, C₆H₃I₂NO₃, the mol­ecules are linked, by an O—H?O hydrogen bond and two iodo–nitro interactions, into sheets, which are further linked into a three‐dimensional framework by aromatic π–π‐stacking interactions. The mol­ecules of 2,6‐di­iodo‐4‐nitro­phenyl acetate, C₈H₅I₂NO₄, lie across a mirror plane in space group Pnma, with the acetyl group on the mirror, and they are linked by a single iodo–nitro interaction to form isolated sheets. The mol­ecules of 2,6‐di­iodo‐4‐nitro­anisole, C₇H₅I₂NO₃, are linked into isolated chains by a single two‐centre iodo–nitro interaction.