Microwave spectrum of gauche normal propyl bromide

The microwave spectra of the two ⁷⁹Br and ⁸¹Br isotopic species of normal propyl bromide were measured in the frequency region 10–30 GHz. The a-type R-branch and b-type Q-branch transitions of one conformer, gauche, were assigned and the rotational constants of the ground state were determined to be A = 11 034.346, B = 2277.725, and C = 2024.525 MHz for the ⁷⁹Br species, and A = 11 027.924, B = 2261.019, and C = 2011.115 MHz for the ⁸¹Br species. The nuclear quadrupole coupling constants were determined to be χ_aa = 256.9, χ_bb = ?9.5, χ_cc = ?247.4, and |χ_ab| = 380.0 MHz for ⁷⁹Br species and χ_aa = 214.1, χ_bb = ?8.1, χ_cc = ?206.0, and |χ_ab| = 311.9 MHz for ⁸¹Br species. Assuming the values of χ_bc and χ_ca to be zero, the principal values of the χ tensor have been evaluated to be χ_xx = ?279.0, χ_yy = ?247.4, χ_zz = 526.4 MHz for ⁷⁹Br species and χ_xx = ?228.1, χ_yy = ?206.0, and χ_zz = 434.1 MHz for ⁸¹Br species. From the relative intensity measurements the energy differences between the ground and first excited states, and the ground and second excited states, associated with the central CC torsion around the α and β carbon bonds were found to be 127 and 211 cm^?1, respectively.     

1,2,4-triazines. 1. A convenient synthesis of 4,5-dihydro-1,2,4-triazin-3-(2H)one and its 6-substituted derivatives

A facile synthesis of 4,5-dihydro-1,2,4-triazin-3-(2H)one (2a) from 5-methylthio-1,2,4-triazin-3-(2H)one (1a) with sodium borohydride is described. The reaction provides a convenient method for its 6-substituted derivatives (2b-h).     

Synthesis of hydrophobic phase-tagged prolyl peptides featuring rapid reaction/separation

Hydrophobically tagged prolyl peptides were synthesized using an electrochemically modified prolyl moiety. The hydrophobic tag served a useful handle for the repetitive reaction/separation steps during solution-phase peptide synthesis. Furthermore, the tag was also effective as an anchor on solid phases for the evaluation of activity of immobilized peptides.     

Energy-flow dynamics in the molecular channel of propanal photodissociation, C2H5CHO --> C2H6 + CO: direct ab initio molecular dynamics study

Direct ab initio molecular dynamics calculations have been carried out for the molecular channel of the photodissociation of propanal, C2H5CHO --> C2H6 + CO, at the RMP2(full)/cc-pVDZ level of ab initio molecular orbital theory. The initial conditions were generated using the microcanonical sampling to put the excess energy randomly into all vibrational modes of the TS. Starting from the TS, a total of approximately 700 trajectories were numerically integrated for 100 fs. The obtained final energy distributions for the C2H6 and CO fragments and their relative translational motion were found to be quite similar to those obtained for the acetaldehyde reaction, CH3CHO --> CH4 + CO, in our previous study (Chem. Phys. Lett. 2006, 421, 549) despite the fact that the number of degree of freedom for C2H6 is larger than that for CH4. The coupling between the intrinsic reaction coordinate and one of the generalized normal modes orthogonal to it was predicted substantially strong around s = 1.4 amu(1/2) bohr, and it is expected that the energy flow out of C2H6 proceeds through this coupling. However, the obtained energy distributions strongly suggest that the coupling among the modes in C2H6 is quite small and the intramolecular energy redistribution does not occur efficiently in this molecule.     

Transition Metal Centered Trigonal Prisms as Building Units in Various Rare Earth–Transition Metal-Indides

Summary. The rare earth–transition metal-indides GdPdIn, ErPdIn, YbPdIn, YPtIn, TmPtIn, Dy₄Pd₁₀In₂₁, PrPt₂In₂, and Tb₂Pt₇In₁₆ were prepared by arc-melting of the elements or by induction melting of the elements in sealed tantalum tubes in a water-cooled sample chamber of a high-frequency furnace. Single crystals of Dy₄Pd₁₀In₂₁ and Tb₂Pt₇In₁₆ were grown through special annealing procedures. The indides were investigated via X-ray powder diffraction and all structures were refined from X-ray single crystal diffractometer data: ZrNiAl type, , a = 767.8(3), c = 390.7(2) pm, wR2 = 0.0722, 356 F² values for GdPdIn; a = 766.7(3), c = 376.7(1) pm, wR2 = 0.0433, 348 F² values for ErPdIn; a = 757.2(2), c = 393.59(8) pm, wR2 = 0.0388, 434 F² values for YbPdIn; a = 758.2(2), c = 384.95(8) pm, wR2 = 0.0643, 353 F² values for YPtIn; and a = 753.4(1), c = 376.71(4) pm, wR2 = 0.0844, 310 F² values for TmPtIn, with 14 variable parameters per refinement. Dy₄Pd₁₀In₂₁ crystallizes with the monoclinic Ho₄Ni₁₀Ga₂₁ structure: C2/m, a = 2284.5(8), b = 441.0(2), c = 1931.4(7) pm, β = 132.74(2)°, wR2 = 0.0419, 1690 F² values, 112 variable parameters. PrPt₂In₂ adopts the CePt₂In₂ type: P2₁/m, a = 1013.2(3), b = 447.2(3), c = 1019.5(3) pm, β = 116.69(2)°, wR2 = 0.0607, 1259 F² values, 63 variable parameters. Tb₂Pt₇In₁₆ is the second representative of the orthorhombic Dy₂Pt₇In₁₆ type: Cmmm, a = 1211.6(2), b = 1997.1(4), c = 440.52(9) pm, wR2 = 0.0787, 1341 F² values, 45 variable parameters. The common structural motif of the four different structure types are transition metal centered trigonal prisms formed by the rare earth metal and indium atoms. These prisms are condensed via common corners or via In–In bonds. The crystal chemistry of the four different structure types is discussed.     

Simple enrichment of thiol‐containing biomolecules by using zinc(II)–cyclen‐functionalized magnetic beads

A simple and efficient method based on magnetic‐bead technology has been developed for the enrichment of thiol‐containing biomolecules, such as l ‐glutathione and cysteine‐containing peptides. The thiol‐binding site on the bead is a mononuclear complex of zinc(II) with 1,4,7,10‐tetraazacyclododecane (cyclen); this is linked to a hydrophilic cross‐linked agarose coating on a particle that has a magnetic core. All steps for the thiol‐affinity separation are conducted in aqueous buffers with 0.10 mL of the magnetic beads in a 1.5 mL microtube. The entire separation protocol for thiol‐containing compounds, from addition to elution, requires less than one hour per sample, provided the buffers and the zinc(II)–cyclen‐functionalized magnetic beads have been prepared in advance. The thiol‐affinity magnetic beads are reusable at least 15 times without a decrease in their thiol‐binding ability, and they are stable for six months at room temperature.     

Preparation and characterization of aqueous colloids of Pt-Ru nanoparticles

A synthetic method for platinum-ruthenium (PtRu) nanoparticles in aqueous media is proposed. This method employs citric acid as a capping agent and NaBH(4) as a reducing agent with the aid of pH control. The number-averaged size of the PtRu nanoparticles was ca. 2 nm. The crystal phase and chemical composition of the nanoparticles was investigated by X-ray diffraction measurement and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis, which indicated that the nanoparticles mainly consisted of an alloy of Pt and Ru. Electrochemical measurement showed that the PtRu nanoparticles had catalytic activity for methanol oxidation.     

A Quadruply Bridged Non-Offset Face-to-Face Porphyrin Dimer and Cross-Shaped Pentameric Porphyrin Tapes Based on 2,7,12,17-Tetrakis(pinacolatoboryl) NiII Porphyrin

2,7,12,17-Tetrakis(pinacolatoboryl) Ni^II porphyrin 5 Ni was synthesized in 75 % yield by Ir-catalyzed borylation of porphine followed by Ni^II metalation and has been demonstrated to be a useful synthon, giving 2,7,12,17-tetraaryated Ni^II porphyrins 6 a – d , peripherally octaarylated Ni^II porphyrins 8 a – d , quadruply bridged face-to-face non-offset Ni^II-porphyrin dimer 12 , and cross-shaped β-meso singly linked porphyrin pentamers and nonamers. Oxidation of cross-shaped β-meso singly linked porphyrin pentamers 14 Ni and 14 Zn gave fused pentameric tapes 15 Ni and 15 Zn . The structures of 12 , 14 Zn , and 15 Ni have been revealed by X-ray diffraction analysis. Optical separation of 12 has been accomplished, showing a bisignate coupling pattern for exciton-coupled blue-shifted Soret band. Pentameric porphyrin tape 15 Zn exhibits a red-shifted absorption band at 1156 nm and seven reversible redox waves.