Search

The quantum state-resolved reactivity S0 of SiH4 on Si(100)-2×1 has been measured for the first time for two vibrationally excited Si–H stretch local mode states (|2000> and |1100>) as well the ground state S0 as a function of translational energy En and surface temperature Ts. We observe evidence for both direct and precursor-mediated chemisorption pathways. As expected, increasing En (or Ts) decreases S0 for the precursor-mediated reaction and increases S0 for the direct chemisorption. However, vibrational excitation of the incident SiH4 increases S0 for both the direct and the precursor-mediated pathway with a higher S0 for the |2000> state than for the |1100> state, indicating a nonstatistical reaction mechanism. [ABSTRACT FROM AUTHOR]

The dressed molecular Hamiltonian for molecules in strong electromagnetic fields is derived in the Bloch–Nordsieck (BN) and electric field (EF) representations beyond the dipole approximation. Both representations, which are related by simple unitary transformations generate photon coherent states beyond the dipole approximation. It is shown that applying the dipole approximation to the complete molecule–field equations leaves recoil corrections of order (v/c) which are field dependent. This implies that in the BN representation all Coulomb potentials will be modified at high intensities. In particular, electron–electron repulsions are subject to field dependent photon recoil corrections, which for very intense fields necessitate relativistic corrections as well. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and photophysical properties of a series of neutral Ir( C N-Meppy)2( O O-tta-Ar) (MeppyH = 4-methyl-2-phenylpyridine; tta = thenoyltrifluoroacetonate) complexes containing new functionalized tta-Ar ligands in which the incorporated Ar group is an aromatic dye such as naphthalene, pyrene, naphthalimide or coumarin, are reported. The arylated proligands ttaH-Ar are readily obtained in two steps through Pd-catalyzed C-H bond activation of 2-acetylthiophene. In contrast to the parent Ir( C N)2( O O) complexes, which are phosphorescent in solution at room temperature, all of the arylated complexes display fluorescence, and the phosphorescence emission is quenched. Thus, this work shows that the incorporation of such aromatic dyes in the tta ligand has a dramatic influence on the photophysical properties of the resulting Ir complexes. [ABSTRACT FROM AUTHOR]

Thieno[3,2-b]thiophene is a structural motif that can be found in many important organic materials. A number of mono-, diand tetraarylthieno[3,2-b]thiophenes are reported herein. [ABSTRACT FROM AUTHOR]

N-Methyl-2,3,4,5-tetrabromopyrrole is transformed into a variety of alkynyl-substituted pyrroles by regioselective Sonogashira cross-coupling reactions. In this context, the synthesis of the first tri- and tetra(1-alkynyl)pyrroles is reported. [ABSTRACT FROM AUTHOR]

An efficient and straightforward method for the synthesis of multi ‐ arylated thieno[3,2 ‐ b]thiophene is reported. The direct site ‐ selective arylation of 2 ‐ arylthieno[3,2 ‐ b]thiophene takes place at predictable positions (i.e., at the C ‐ 3 or C ‐ 5 position) depending on the nature and the size of the 2 ‐ aryl substituents. If the 2 ‐ aryl substituent bears an electron ‐ withdrawing group, the next arylation takes place at the C ‐ 3 position. On the other hand, if the 2 ‐ aryl substituent bears an electron ‐ donating group, the next arylation takes place at the C ‐ 5 position. More information can be found in the Full Paper by Tung Thanh Dang, Hien Nguyen et   al. on page   2819 in Issue 21, 2017 (DOI:10.1002/asia.201700562). [ABSTRACT FROM AUTHOR]

Mono-, di-, tri-, and tetraarylated thieno[3,2-b]thiophenes were synthesized by direct site-selective Pd-catalyzed C-H activation reactions with various aryl bromides in the presence of a phosphine-free Pd(OAc) 2 /KOAc catalyst system in N,N-dimethylacetamide (DMAc). The arylation of 2-arylthieno[3,2-b]thiophene took place at the C3 position if the 2-aryl substituents possessed electron-withdrawing groups and at the C5 position if they were bulky and possessed electron-donating groups., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The synthesis and the characterization of two porphyrin coordination cages are reported. The design of the cage formation is based on the coordination of silver(I) ions to the pyridyl units of 3-pyridyl appended porphyrins. (1)H/(109)Ag NMR spectroscopy, and diffusion-ordered spectroscopy (DOSY) experiments demonstrate that both the free base porphyrin 2H-TPyP and the Zn-porphyrin Zn-TPyP form the closed cages, [Ag4(2H-TPyP)2](4+) and [Ag4(Zn-TPyP)2](4+), respectively, upon addition of two equivalents of Ag(+). The complexation processes are characterized in details by means of absorption and emission spectroscopy in diluted CH2Cl2 solutions. The data are discussed in the frame of the point-dipole exciton coupling theory; the two porphyrin monomers, in fact, experience a rigid face-to-face geometry in the cages and a weak inter-porphyrin exciton coupling. An intermediate species is observed, for Zn-TPyP, in a porphyrin/Ag(+) stoichiometric ratio of about 1:0.5 and is tentatively ascribed to an oblique open form. The occurrence of a photoinduced electron-transfer reaction within the cages is excluded on the basis of the experimental outcomes and thermodynamic evaluations. Photophysical experiments evidence different reactivities of singlet and triplet excited states in the assemblies. A lower fluorescence quantum yield and triplet formation is discussed in relation to the constrained geometry of the complexes. Unusually long triplet excited state lifetimes are measured for the assemblies., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)