Synthesis of 1,2-Epoxy-1,2,3,4-Tetrahydrobenzo[g]chrysene: The First Synthesis of a FJORD-Region Tetrahydroepoxide

This study describes the first synthesis of a fjord-region tetrahydroepoxide (11), derived from the carcinogenic hydrocarbon benzo[g]chrysene. This compound is a more potent DNA alkylating agent than the corresponding 3,4-diol 1,2-epoxide.     

Sol-flame synthesis of hybrid metal oxide nanowires

Hybrid metal oxide nanowires (NWs), with small characteristic diameter and large aspect ratio, can have unique and yet tunable chemical, optical and electrical properties by independently controlling the chemical compositions and morphologies of the individual components. Such hybrid NWs are promising building blocks in many applications, such as catalysis, sensors, batteries, solar cells and photoelectrochemical devices. However, these applications are hindered by the lack of scalable and economic methods for the synthesis of hybrid NWs. Here, we report a simple, scalable and new sol-flame method to synthesize various hybrid metal oxide NWs, including nanoparticle-shell decorated NWs (NP-shell@NW), NP-chain decorated NW (NP-chain@NW) and doped NWs. The sol-flame process first coats existing NWs with NPs or dopants precursors prepared by the sol–gel process, and then dissociates/oxidizes these precursors in flame. The sol-flame method uniquely combines the merits of the flame process (e.g., high temperature and fast heating rate) with low temperature sol–gel method (e.g., broad material choices and excellent chemical composition control). For both the NP-shell@NW and NP-chain@NW cases, the high temperature flame, compared to furnace, provides much faster heating rate and shorter duration for annealing, which evaporates and burns the precursor solvent rapidly, causing NPs to quickly nucleate around NWs without significant agglomeration. Hence, higher loading density of NPs with smaller sizes is decorated to the NWs, and the formed hybrid NP@NW exhibits significantly higher catalytic activity than that of the furnace-annealed sample. Similarly when using the sol-flame method to dope NWs, the high temperature flame enables rapid dopant diffusion and short annealing duration that maintains the morphology of the original materials and protects the delicate NW substrates from damage. We believe that the new sol-flame method can be applied to synthesize various 1-D hybrid metal oxide nanostructures, thereby impacting diverse application fields.     

Improved TLC systems for rapid resolution of phenyl thiohydantoin amino acids

Two new solvent systems, n-hexane + propionic acid (26:5, v/v) and chloroform + acetone (29:3, v/v), for the rapid resolution and identification of an 18-component mixture of phenylthiohydantoin amino acids are reported. Using these systems certain difficult combinations of phenylthiohydantoin amino acids are resolved. Two more solvent systems, viz chloroform + acetic acid (27:3, v/v) and chloroform + methanol (30:4, v/v), are developed to resolve phenylthiodantoin derivatives of aspartic and glutamic acids.     

Stable ion study of benzo[a]pyrene (BaP) derivatives: 7,8-dihydro-BaP, 9,10-dihydro-BaP and its 6-halo derivatives, 1- and 3-methoxy-9,10-dihydro-BaP-7(8H)-one,as well as the proximate carcinogen BaP 7,8-dihydrodiol and its dibenzoate,combined with a comparative DNA binding study of regioisomeric (1-, 4-, 2-) pyrenylcarbinols

A stable ion study of a series of BaP derivatives is reported. 7,8-Dihydro-BaP 1 gives a persistent bay-region benzyliclike carbocation which shows extensive charge delocalization into the pyrene moiety. In contrast, a "benzylic" carbocation can not be generated from 9,10-dihydro-BaP 2. Introduction of bulky substituents at peri C-6 of 9,10-dihydro-BaP (as in 4 and 5) prevents side reactions (dimerization) to the extent that the initially formed carbocation undergoes rearrangement to generate the corresponding bay-region "benzylic" carbocation as a persistent species. Introduction of methoxy substituents into the 1- or 3-positions of 9,10-dihydro-BaP-7(8H)-one (6,7) increases its electrophilic reactivity to the extent that stable carboxonium-arenium dications are produced in FSO3H-SO2ClF. A detailed NMR study (at 500 MHz) of the resulting mono- and dications is reported, and charge delocalization mode (as well as conformational aspects) are addressed. Other oxidized derivatives of BaP such as the 7,8-dihydrodiol 9 and the 7,8-dihydrodibenzoate 8 are not suitable models for stable ion study because of competing O-protonation (and elimination). Energies for various possible arenium ions and regioisomeric "benzylic" cations were computed by the DFT method at the B3LYP/6-31G(d)//B3LYP/6-31G(d) level or by AM1 for comparison with the experimental results. These findings provide further evidence in support of the stability sequence: 1-pyrenyl > 4-pyrenyl > 2-pyrenyl in alpha-pyrene-substituted carbocations as models for the intermediates arising from BaP-epoxide ring opening. In an effort to provide a parallel, a series of alpha-pyrenylcarbinols were subjected to a DNA binding study using human MCF-7 cells. The results/trends are discussed and compared with the stable ion data.     

Meet the Board of ChemistryOpen: Sheshanath V. Bhosale

Sheshanath V. Bhosale received his PhD from Freie University Berlin (Germany) in supramolecular chemistry under the supervision of Prof. J. H. Fuhrhop in 2004. He then pursued his postdoctoral studies with Prof. S. Matile at University of Geneva (Switzerland) under the auspices of a Roche Foundation Fellowship. This was followed by a stay at Monash University (Australia) for 5 years as an ARC-APD Fellow. He worked at RMIT University, Melbourne (Australia) for 6 years as ARC-Future Fellowship. Currently, Prof. Bhosale is working at the Department of Chemistry, Goa University (India) as a UGC-FRP Professor, His research interests lie in the design and synthesis of π-functional materials, especially small molecules, for sensing, biomaterials, and supramolecular chemistry applications. So far, Prof. Bhosale has produced 185 research articles and his work has been cited more than 4400 times, giving him an h-index of 32. He currently serves as an active Editorial Board member for ChemistryOpen.     

Water-soluble dendrimers as photochemical reaction media: chemical behavior of singlet and triplet radical pairs inside dendritic reaction cavities

Water-soluble poly(alkyl aryl ether) dendrimers have been explored for their use as hosts of organic substrates in aqueous media. Prototypical photoreactions, namely, photo-Fries reaction of (a) 1-naphthyl benzoate and (b) 1-naphthyl phenyl ester and alpha-cleavage reaction of (a) dibenzyl ketones and (b) benzoin alkyl ethers, have been examined. We find that a dendritic microenvironment not only restricts the mobility of radical intermediates but also rigidly encapsulates the substrate, intermediates, and products from "leaking" to the bulk environment. Comparative studies of the same photoreactions in micellar media demonstrate that dendritic media offer much better constrainment than the micelles.     

Microarrays of tagged combinatorial triazine libraries in the discovery of small-molecule ligands of human IgG

A novel and highly diverse tagged triazine library incorporating a triethylene glycol-based linker was synthesized using an orthogonal combinatorial approach on the solid phase and covalently immobilized on a glass substrate as a small molecule microarray (SMM). The SMM was screened with a fluorophore-conjugated human IgG, and 4 novel binders from a library of 2688 compounds were identified from the fully spatially addressable array without the need for compound decoding. Using surface plasmon resonance (SPR) analysis, binding seen on the array was confirmed, and a binding constant as low as Kd = 2.02 x10(-6) M was measured.     

Role of capillary stresses in film formation

Stresses generated during film formation were deduced from the deflection of a copper cantilever coated with a drying latex. Experiments with particles of varying radii and glass transition temperatures (Tg) focused on conditions for which capillary stresses normal to the film deform the particles to close the voids. Soft particles (low Tg) formed continuous films, but hard ones (high Tg) produced fascinating arrays of cracks. For both soft and rigid particles, the lateral stresses were tensile and scaled on the surface tension divided by the particle radius. Clearly, tensile stresses in the plane of the film responsible for cracking arise from the same capillary pressure that drives compression in the normal direction. Solving the model (Routh & Russel 1996, 1999) for lateral flow of the fluid dispersion prior to close packing and deformation of the solid beyond close packing yields volume fraction, film thickness, and stress profiles for comparison with observations for both film-forming and film-cracking cases.