The crystal and molecular structures of isoperezone, aminoperezone, and isoaminoperezone: a comparative study of their crystal packing

The crystal structures of isoperezone (1), aminoperezone (2), and isoaminoperezone (3) have been determined by single-crystal X-ray diffraction. Compound (1) yields orange crystals, orthorhombic space group P2₁2₁2₁ with unit cell dimensions a = 6.271(6), b = 30.373(7), c = 7.257(1) Å, and Z = 4; compound (2) yields purple crystals, orthorhombic space group P2₁2₁2₁ with unit cell dimensions a = 6.498(3), b = 7.500(1) c = 29.200(6) Å, and Z = 4; compound (3) yields purple crystals, monoclinic space group P2₁ with unit cell dimensions a = 7.354(1), b = 7.511(1), c = 13.283(1) Å, = 102,07(1)°, and Z = 2. The side chains in (1)–(3) are oriented out of the plane of the quinone ring at an angle of 124, 144, and 97°, respectively. The molecules in the crystal are held together by hydrogen-bonding networks and van der Waals interactions.     

Crystal structures of [WI2(CO)3{Ph2P(CH2) n PPh2}] (n = 2 or 3)

[WI₂(CO)₃{Ph₂P(CH₂)₂PPh₂}] (1) crystallizes out in the monoclinic space group P2₁/n, with a = 13.852(7) Å, b = 14.789(19) Å, c = 14.915(19) Å, = 102.86(1)°, Z = 4. [WI₂(CO)₃{Ph₂P(CH₂)₃PPh₂}] (2) crystallizes out in the monoclinic space group P2₁/n, with a = 10.499(15) Å, b = 14.58(2) Å, c = 20.75(3) Å, = 103.59(1)°, Z = 4. Both structures show the metal in a seven-coordinate environment with a carbonyl in the unique capping position, two further carbonyls and a phosphorus in the capped face, and two iodides and the second phosphorus in the uncapped face.     

Simplified syntheses of complex multifunctional nanomaterials

Multifunctional probes are synthesized in a single step using peptide scaffold-based multifunctional single-attachment-point (MSAP) reagents.     

Effectiveness of the suzuki-miyaura cross-coupling reaction for solid-phase peptide modification

The Suzuki-Miyaura (SM) cross-coupling reaction has recently become one of the most efficient methods for C-C bond construction opening a wide range of opportunities in organic synthesis. This study focused on the evaluation of the use of the SM reaction to modify peptides using a solid-phase synthesis approach, an avenue that was still not investigated intensively. We used as a peptide model [Ala (1,2,3), Leu (8)]Enk linked to a polystyrene support on which it was previously assembled. The aromatic residues Tyr (4) and Phe (7) of [Ala (1,2,3), Leu (8)]Enk were respectively substituted with p-iodo-Phe, and an SM-related strategy was developed. Results indicated that the reaction conditions involving K 3PO 4 or Na 2CO 3 (base), DMF (solvent), Pd(PPh 3) 4 (catalyst), and temperatures ranging from 50 to 80 degrees C during 20 h were found as optimal. Finally applying those optimal conditions, a series of [Ala (1,2,3), Leu (8)]Enk analogs modified at Tyr (4) or Phe (7) positions was synthesized using diverse boronic acid derivatives.     

Single-particle tracking of janus colloids in close proximity

We describe algorithms and an experimental method based on differential interference contrast microscopy to discriminate optically anisotropic colloidal spheres under situations where diffraction owing to their close proximity causes overlapping images. The data analysis is applied to modulated optical nanoprobes (MOONs) that are coated with metal on one hemisphere. These methods enable single-particle tracking of rotation in addition to translation not only in concentrated suspensions but also in dilute suspensions when particles come into transient hydrodynamic contact. An illustrative example is given.     

Solvent-free synthesis of Janus colloidal particles

Taking advantage of the quick and efficient access of vapor to surfaces, a simple, solvent-free method is demonstrated to synthesize Janus colloidal particles in large quantity and with high efficiency. First, at the liquid-liquid interface of emulsified molten wax and water, untreated silica particles adsorb and are frozen in place when the wax solidifies. The exposed surfaces of the immobilized particles are modified chemically by exposure to silane vapor and, in principle, subsequent dissolution of the wax opens up the inner particle surface for further chemical modification. Applying this scheme, this paper describes the production of amphiphilic Janus particles (hydrophobic on one side, hydrophilic on the other) and dipolar Janus particles (positively charged on one side, negatively charged on the other). Janus geometry is confirmed by fluorescence microscopy and flow cytometry. Amphiphilic Janus particles are found to adsorb strongly to the water-oil interface, whereas dipolar particles assemble into chains in the aqueous phase.     

Discrete photopatternable pi-conjugated oligomers for electrochromic devices

Three discrete oligomeric systems including an all-thiophene ( T6) system, a thiophene/phenylene ( TPTTPT) system, and a thiophene/EDOT/phenylene ( TPEEPT) system have been constructed and characterized with emphasis on structural, optical, electrochemical, and spectroelectrochemical properties. For all three chromophores, the radical cation, the dication, and the pi-dimer have been identified and characterized. EPR spectroscopy reveals that the radical cations of TPTTPT and TPEEPT have g values of 2.008-2.012 and peak-to-peak widths in the range 4.2-5.3 G. Formation of the radical cation takes place at a lower potential for TPEEPT than for TPTTPT and T6, whereas subsequent oxidation to the dication occurs more easily for TPTTPT than for TPEEPT and T6. We ascribe this observation to more localized charges in the oxidized species of TPEEPT, which is supported by our finding that the radical cation of TPEEPT is less prone to undergo pi-dimerization than the radical cations of TPTTPT and T6. All the oxidized species are sufficiently stable to allow for optical characterization, and the relative positions of all absorption bands are found to be in agreement with the electrochemical data. For further solid-state modifications of these materials, we have effectively modified the synthetic design and grafted terminal functionalities (e.s. acrylates) onto the discrete oligomers. Of these novel materials, TPEEPT proves to be the most promising anodically coloring material for electrochromics, and it undergoes reversible switching between two different colored states (bright yellow and clear blue) and one almost transparent and color neutral state. Contrast ratios, measured as Delta% T at lambda max, are as high as 62.5%, and switching times are in the range 2-5 s for the coloration process, though significantly longer for the bleaching process. As a proof of concept, we have successfully constructed a simple photopatterned electrochromic device by exploiting the terminal acrylate functionalities of the oligomers in a UV-initiated cross-linking process. To the best of our knowledge, this is the first oligomer-based photopatterned electrochromic device reported in the literature.     

Rapid analysis of N-methylpyrrolidine in cefepime with thermal desorption ion mobility spectrometry

N-methyl-pyrrolidine (NMP) a potential impurity in the cephalosporin antibiotic cefepime is analysed using a rapid thermal desorption – ion mobility spectrometry (TD-IMS) method. The thermal desorption approach is shown to be capable of rapidly extracting NMP from the cefepime at 80 °C without causing thermal degradation of the cefepime. The ion mobility method has an analysis time of 1 min and demonstrates good linearity over a range from 0.3–3.0 μg ml^?1 of NMP, with limits of detection and quantification of 0.056 and 0.1875 μg ml^?1 respectively. The developed method was applied to the analysis of a cefepime sample and determined that NMP was present in a cefepime sample at a level of 0.0376 % with a percentage relative standard deviation (n = 6) of 3.2 %. This was compared with a LC-UV method which was in close agreement measuring NMP at 0.0384 % in the cefepime sample with a percentage RSD (n = 6) of 5.7 %. These results show that the TD-IMS method gives comparable data to the established LC methods and demonstrates the potential of TD-IMS for rapid measurement of volatile compounds in pharmaceutical matrices.