Mixed‐Valent Molecular Triple Deckers

Two phenothiazine (PTZ) moieties were connected via naphthalene spacers to a central arene to result in stacked PTZ‐arene‐PTZ structure elements. Benzene and tetramethoxybenzene units served as central arenes mediating electronic communication between the two PTZ units. Based on cyclic voltammetry, UV/Vis‐NIR absorption, EPR spectroscopy, and computational studies, the one‐electron oxidized forms of the resulting compounds behave as class II organic mixed‐valence species in which the unpaired electron is partially delocalized over both PTZ units. The barrier for intramolecular electron transfer depends on the nature of the central arene sandwiched between the two PTZ moieties. These are the first examples of rigid organic mixed‐valent triple‐decker compounds with possible electron‐transfer pathways directly across a stacked structure, and they illustrate the potential of oligo‐naphthalene building blocks for long‐range electron transfer and a future molecular electronics technology.     

Four-Dimensional Compact Projective Planes with Collineation Group N6,28

We consider a 4-dimensional compact projective plane $\pi = ({\cal P},{\cal L})$ ?e whose collineation group σ is 6-dimensional and solvable with a 4-dimensional nilradical N. We assume that σ fixes a flag υ ∈ W, acts transitively on ${\cal L}_{\upsilon}\setminus \lbrace W \rbrace$ ?e, and fixes no point in the set W{υ}. If π is neither a translation plane nor a dual translation plane, nor a shift plane, then we will show that ?(N) ? nil × R, i.e. the local structure of N is uniquely determined.     

Double-chip protein arrays: force-based multiplex sandwich immunoassays with increased specificity

Protein assays provide direct access to biologically and pharmacologically relevant information. To obtain a maximum of information from the very smallest amounts of complex biological samples, highly multiplexed protein assays are needed. However, at present, cross-reactions of binding reagents restrict the use of such assays to selected cases and severely limit the potential for up-scaling the technology. Here we describe a double-chip format, which can effectively overcome this specificity problem for sandwich immunoassays. This format consists of a capture array and a reference array with fluorescent labeled detection antibodies coupled to the reference array via DNA duplexes. This format allows for the local application of the labeled detection antibodies onto their corresponding specific spots on the capture array. Here we show that this double-chip format allows for the use of cross-reactive antibodies without generating false positive signals, and an assay for the parallel detection of seven different cytokines was set up. Even without further optimization, the dynamic range and the limit of detection for interleukin 8 were found to be comparable to those obtained with other types of multiplexed sandwich immunoassays.     

Electronic structures of organometallic complexes of f elements. Part 54. Electronic Raman and f-f transitions in the low temperature vibrational spectra of Cp3Ce(NCCH3)2

A comparison of the low temperature Raman spectra of Cp(3)Ce(NCCH(3))(2) (1), Cp(3)La(NCCH(3))(2) (2), Cp(3)La(NCCH(3))(2):Pr(3+) (3), Cp(3)La x NCCH(3) (4), Cp(3)Ce x NCCH(3) (5) and Cp(3)Tb x NCCH(3) (6) shows that the former compound exhibits three additional bands at 320, 2129 and 2154 cm(-1), which we ascribe to electronic Raman transitions. The two latter signals also appear in the low temperature IR spectrum of complex 1, but not in those of compounds 2-6. By performing crystal field (CF) calculations, the terminal states of the observed electronic Raman transitions could be identified. On the basis of both experimental and calculated CF energies as well as calculated wave functions the observed temperature dependence of mu(2)(eff) of complex 1 could be simulated in a satisfactory manner. A comparison of the low temperature Raman spectrum of compound 1 with the low temperature FIR spectrum of complex 2 shows that the selection rules for trigonal-bipyramidal coordination do not hold strictly for the skeletal vibrations. If the additional criterion of allowed vibronic side bands is applied to the transitions Gamma(1)-->Gamma(1, 4, 5, 6) of compound 3, the observed vibrational energies may be partly classified according to their symmetry.     

Fullerenes (C60) versus heteroazafullerenes (C59N); a photophysical comparison of their monoadducts and hexaadducts

The singlet and triplet excited state properties of a series of fullerene derivatives (C₆₀) are compared to those of the corresponding heteroazafullerenes derivatives (C₅₉N) by employing a variety of steady-state and time-resolved photophysical assays. The most far-reaching results infer that the C₅₉N (2, 5) analogous of C₆₀ (1, 4) are characterized by shorter singlet lifetimes (1.01/0.57 ns versus 1.80/1.75 ns) and weaker fluorescence quantum yields (1.6 × 10^-4/2.1 × 10^-4 versus 6.0 × 10^-4/1.09 × 10^-3). This general conclusion applies for the monoadduct series (1, 2) and also for the highly functionalized hexaadducts (4, 5). Similarly, higher singlet energies (1.89 eV (4) versus 1.79 eV (1)) come together with higher fluorescence quantum yields for the hexaadducts than for the monoadducts.     

Molecular satellite dishes: attaching parabolic and planar arenes to heterofullerenes

The electrophilic attack of C(59)N(+) on arenes such as pyrene, coronene and corannulene leads to the regioselective formation of fullerene conjugates, in which polycyclic aromatics are connected to the spherical heterofullerene by a single sigma-bond.     

Zur Elektronenstruktur hochsymmetrischer Verbindungen der f‐Elemente. 42 Ableitung und Simulation des Kristallfeld‐Aufspaltungsmusters von Tris(bis(trimethylsilyl)amido)ytterbium(III)

Electronic Structures of Highly Symmetrical Compounds of f Elements. 42 Derivation and Simulation of the Crystal Field Splitting Pattern of Tris(bis(trimethylsilyl)amido)ytterbium(III) Tris(bis(trimethylsilyl)amido)ytterbium(III), (Yb(btmsa)₃ ( 1 )) was grown as a single crystal of the size 6×2×2 mm. The unpolarized absorption and luminescence as well as the σ and π absorption spectra of this crystal were recorded at room and low temperatures. The observed polarization properties as well as identificational calculations allowed the separation of zero‐phonon‐ and phonon‐assisted transitions of comparable intensities. The thus derived crystal field splitting pattern could be simulated by fitting the free parameters of a phenomenological Hamiltonian. In order to assign the coupling vibrations, FIR/MIR‐ and unpolarized Raman spectra of 1 as well as polarized Raman spectra of Y(btmsa)₃ ( 2 ) were recorded and compared with previously assigned ones of MeGa(btmsa)₂ and H(btmsa).     

Elucidating the Reactivity of Vicinal Dicarbenoids: From Lewis Adduct Formation to B−C Bond Activation

The reactivity of the diaminoacetylene Pip‐C≡C‐Pip (Pip=piperidyl=NC₅H₁₀) towards phenyldichloro‐ and triphenylborane is presented. In the case of the less Lewis acidic PhBCl₂, the first example of a double Lewis adduct of a vicinal dicarbenoid is reported. For the more Lewis acidic triphenylborane, coordination to the bifunctional carbene leads to a mild B?C bond activation, resulting in a syn‐1,2‐carboboration. Ensuing cis/trans isomerization yields a novel ethylene‐bridged frustrated Lewis pair (FLP). The compounds were characterized using multinuclear NMR spectroscopy, structural analysis, and mass spectrometry. Reactivity studies of both isomers with the N‐heterocyclic carbene 1,3‐dimethylimidazol‐2‐ylidene (IMe) aided in elucidating the proposed isomerization pathway. DFT calculations were carried out to elucidate the reaction mechanism. The rather low free energy of activation is consistent with the observation that the reaction proceeds smoothly at room temperature.     

Few‐Layer Antimonene by Liquid‐Phase Exfoliation

We report on a fast and simple method to produce highly stable isopropanol/water (4:1) suspensions of few‐layer antimonene by liquid‐phase exfoliation of antimony crystals in a process that is assisted by sonication but does not require the addition of any surfactant. This straightforward method generates dispersions of few‐layer antimonene suitable for on‐surface isolation. Analysis by atomic force microscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy confirmed the formation of high‐quality few‐layer antimonene nanosheets with large lateral dimensions. These nanolayers are extremely stable under ambient conditions. Their Raman signals are strongly thickness‐dependent, which was rationalized by means of density functional theory calculations.     

Collineations of V-Spaces

V-spaces are special non-planar ³-spaces in the sense of Betten. The group of collineations of a given V-space is a Lie group of dimension at least 4. We will determine all V-spaces with a large collineation group. If the V-space is generated by a function f, then dim 5 implies f(x)=c|x| ^p for some constants c>0, p>1.