Synthesis and characterization of a coordinated oxoborane: Lewis acid stabilization of a boron-oxygen double bond

The first example of a stable oxoborane monomer (LB=O) stabilized by complexation to AlCl3 has been prepared by the reaction of LAlCl2 with BCl3 followed by treatment with H2O in CH2Cl2 (L = [HC(CMe)2(NC6F5)2]). DFT calculations reveal that considerable boron-oxygen double bond character is retained in this complex.     

"Smart dust": nanostructured devices in a grain of sand

The term "smart dust" originally referred to miniature wireless semiconductor devices made using fabrication techniques derived from the microelectronics industry. These devices incorporate sensing, computing and communications in a centimetre-sized package. This article discusses the construction of much smaller silicon-based systems, using the tools of nanotechnology. The synthesis of millimetre- to micron-sized functional photonic crystals made from porous silicon is described. It is shown how the various optical, chemical, and mechanical properties can be harnessed to perform sensing, signal processing, communication and motive functions.     

A luminescent linear trinuclear magnesium complex assembled from a phosphorus-based tris-hydrazone ligand

A novel linear trinuclear magnesium complex (P(S)[N(CH3)N=CHC6H4-o-O]3)2Mg3 was prepared by the reaction of P(S)[N(CH3))N=CHC6H4-o-OH]3 with MgCl2 x 6H2O in the presence of triethylamine. The trinuclear magnesium complex is fluorescent in solution as well as in the solid-state.     

The crystal structure of the 'pentamethylcyclopentadienyl cation' is that of the pentamethylcyclopentenyl cation

The recently reported X-ray crystal structure of the [B(C6F5)4]- salt of the 'pentamethylcyclopentadienyl cation' is actually that of pentamethylcyclopentenyl tetrakis(pentafluorophenyl)borate.     

Real‐time monitoring of the ring‐opening polymerization of rac‐lactide with in situ attenuated total reflectance/Fourier transform infrared spectroscopy with conduit and diamond‐composite sensor technology

Polymerization rates were proportional to initial Sn(Oct)₂ concentration at low [Sn(Oct)₂]₀/[PrOH]₀ values, but began to level off at higher values. When [Sn(Oct)₂]₀/[PrOH]₀ was significantly greater than unity, the opposite behavior occurred. Tin(II) alkoxide concentration became limited by the initial PrOH concentration and independent of initial Sn(Oct)₂ concentration. Addition of 2‐ethylhexanoic acid caused polymerization rate retardation, without affecting molecular weight. A control polymerization was conducted in the absence of PrOH. The molecular weight of the resulting polymer was consistent with the measured water content (3.7 wt % by Karl Fisher titration) of the as‐received Sn(Oct)₂. The polymerization rate in the absence of PrOH was slow, and this suggested that water is less efficient than an alcohol in creating polymerization‐active stannyl ether bonds. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6238–6247, 2004     

Role of pore size on the electrochemical oxidation of 5-hydroxytryptophan in a silica sol–gel matrix

Silica sol–gels that are prepared by room-temperature processing are suited as matrices for voltammetry in the absence of a contacting liquid phase because the electrolyte encapsulated within the pore volume supports charge transport. We hypothesized that when the electrode process involves a coupled chemical reaction, the pore size can influence the product distribution. This hypothesis was tested with 5-hydroxytryptophan (5-HTPP) as the electroactive species because the cation radical formed by its oxidation can react to form a simple dione or larger dimer, trimer, and oligomer products. Microporous and mesoporous silica sol–gels, which have respective pore diameters in the Å and nm ranges, were the solid-state electrolytes. Glassy carbon (GC) electrodes were used initially; however, experiments in aqueous solution showed that passivation precluded applications in a solid electrolyte. Boron-doped diamond (BDD) electrodes yielded the same voltammetric signature as that of GC but passivated more slowly. In accord with the hypothesis, the oxidation of 5-HTPP at BDD in microporous silica yielded voltammetry suggesting that dione formation was the primary oxidation pathway. With mesoporous silica, the analogous experiment suggested dimer formation. The voltammetric interpretation was consistent with the results obtained by chemical oxidation of 5-HTPP in these matrices followed by product identification by mass spectrometry.     

An analysis of the rotational, fine and hyperfine effects in the (0, 0) band of the AΠ-XΣ transition of manganese monohydride, MnH

High-resolution (±0.003 cm⁻¹), laser induced fluorescence (LIF) spectra of a supersonic molecular beam sample of manganese monohydride, MnH, have been recorded in the 17500-17800 cm⁻¹ region of the (0, 0) band of the A⁷Π-X⁷Σ ⁺ system. The low-N branch features were modeled successfully by inclusion of the magnetic hyperfine mixings of spin components within a given low-N rotational level using a traditional ‘effective’ Hamiltonian approach. An improved set of spectroscopic constants has been extracted and compared with those from previous analyses. The optimum optical features for future optical Stark and Zeeman measurements are identified.