Os(bpy)2(CO)(enIA)][OTf]2: a novel sulfhydryl-specific metal-ligand complex

The synthesis and physical-chemical characterization of the metal-ligand complex [Os(bpy)2(CO)(enIA)][OTf]2 (where enIA = ethylenediamine iodoacetamide) with a sulfhydryl-specific functional group is described. The UV and visible absorption and luminescence emission, including lifetime and steady-state anisotropy, are reported for the free probe and the probe covalently linked to two test proteins. The spectroscopic properties of the probe are unaffected by chemical modification and subsequent covalent linkage to the proteins. The luminescence lifetime in aqueous buffer is approximately 200 ns and the limiting anisotropy is greater than 0.125, suggesting a potentially useful probe for biophysical investigations.     

Structural reinvestigation of ammonium hypophosphite: was dihydrogen bonding observed long ago?

The past decade has seen the explosive emergence of "dihydrogen bonds", interactions between the electrons of M-H sigma-bonds, where M is less electronegative than H (M = Al, B, Ga, Ir, Mo, Mn, Os, Re, Ru, W) and traditional proton donors. But 70 years ago, such an interaction was proposed by Zachariasen and Mooney [J. Chem. Phys. 1934, 2, 34-37] on the basis of their single-crystal X-ray diffraction structure (heavy atoms positions only) of ammonium hypophosphite (NH(4)H(2)PO(2)). We redetermined this structure at high resolution with a focus on the hydrogen atoms, using a modern diffractometer equipped with a CCD detector. Molecular orbital calculations were performed to investigate the charge density and the bond polarity of the P-H bonds and to assess their potential for participation in dihydrogen bonds. Neither the theory nor the X-ray structure supports the original claim of H...H interactions in this salt.     

Cationic bis-cyclometalated iridium(III) diimine complexes and their use in efficient blue, green, and red electroluminescent devices

A series of cationic Ir(III) complexes with the general formula (C/N)2Ir(N/N)(+)PF6- featuring bis-cyclometalated 1-phenylpyrazolyl-N,C2' (C/N) and neutral diimine (N/N, e.g., 2,2'-bipyridyl) ligands were synthesized and their electrochemical, photophysical, and electroluminescent properties studied. Density functional theory calculations indicate that the highest occupied molecular orbital of the compounds is comprised of a mixture of Ir d and phenylpyrazolyl-based orbitals, while the lowest unoccupied molecular orbital has predominantly diimine character. The oxidation and reduction potentials of the complexes can be independently varied by systematic modification of either the C/N or N/N ligands with donor or acceptor substituents. The electrochemical redox gaps (E(ox)-E(red)) were adjusted to span a range between 2.39 and 3.08 V. All of the compounds have intense absorption bands in the UV region assigned to 1(pi-pi*) transitions and weaker charge-transfer (CT) transitions that extend to the visible region. The complexes display intense luminescence both in fluid solution and as neat solids at 298 K that is assigned to emission from a triplet metal-ligand-to-ligand CT (3MLLCT) excited state. The energy of the 3MLLCT state varies in nearly direct proportion to the size of the electrochemical redox gap, which leads to emission colors that vary from red to blue. Three of the (C/N)2Ir(N/N)(+)PF6- complexes were used as active materials in single-layer light-emitting electrochemical cells (LECs). Single-layer electroluminescent devices were fabricated by spin-coating the Ir complexes onto an ITO-PEDOT/PSS substrate followed by deposition of aluminum contacts onto the organic film. Devices were prepared that give blue, green, and red electroluminescence spectra (lambda(max) = 492, 542, and 635 nm, respectively), which are nearly identical with the photoluminescence spectra of thin films of the same materials. The single-layer LECs give peak external quantum efficiencies of 4.7, 6.9, and 7.4% for the blue, green, and red emissive devices, respectively.     

Charge propagation in "ion channel sensors" based on protein-modified electrodes and redox marker ions

The mechanism of charge propagation in "ion channel sensors" (ICSs) consisting of gold electrodes modified with a layer of charged proteins and highly charged redox-active marker ions in solution was investigated by electrochemical techniques, QCM and AFM. The study is based on seven proteins (concanavalin A, cytochrome c, glucose oxidase, lysozyme, thyroglobulin, catalase, aldolase, and EF1-ATPase) in combination with seven electroactive marker ions ([Fe(CN)6]3-, [Fe(CN)6]4-, [Ru(NH3)6]3+, mono-, di-, and trimeric viologens), as well as a series of suppressor and enhancer ions leading to the following general statements: (i) electrostatic binding of charged marker ions to the domains of the protein is a prerequisite for an electrochemical current and (ii) charge propagation through the layer consists of electron hopping along surface-confined marker ions into the pores between adsorbed proteins. It is further shown that (iii) marker ions and suppressor ions with identical charge compete for oppositely charged sites on the protein domain, (iv) electrostatically bound multilayers of marker or enhancer ions with alternating charge form on a charged protein domain, and (v) self-exchange and exergonic ET catalysis between adsorbed marker ions and marker ions in solution take place. In addition to fundamental insight into the mechanism of charge propagation, valuable information for the design, optimization, and tailoring of new biosensors based on the ICS concept is demonstrated by the current findings.     

Vectorial Approach to Fast Correlation Attacks

A new, vectorial approach to fast correlation attacks on binary memoryless combiners is proposed. Instead of individual input sequences or their linear combinations, the new attack is targeting subsets of input sequences as a whole thus exploiting the full correlation between the chosen subset and the output sequence. In particular, the set of all the input sequences can be chosen as the target. The attack is based on a novel iterative probabilistic algorithm which is also applicable to general memoryless combiners over finite fields or finite rings. To illustrate the effectiveness of the introduced approach, experimental results obtained for random balanced combining functions are presentedMost of this work was done while he was with Rome CryptoDesign Center, Gemplus, Italy     

An exact solution for a cavity model

Résumé On considère l'écoulement plan, permanent et irrotationnel d'un jet gazeux aux grandes vitesses subsoniques. En appliquant le procédé deFalkovich, concernant la méthode hodographique deChaplygin, on obtient la solution exacte pour le modèle de Roshko situé dans un canal aux parois parallèles (Figure). On détermine l'expression exacte du coefficient de résistance et on donne quelques relations entre les différents paramètres de la configuration.     

Über die Struktur des Hydrazinium-Monofluorids

Zusammenfassung Hydrazinium-Monofluorid N₂H₅F, das einzige noch unbekannte Hydrazinium-Monohalogenid, wurde im Nuklearinstitut Joef Stefan synthetisiert. Farblose durchsichtige nadelförmige Kristalle (Dichte 1,47 g/cm³) wurden uns für eine Strukturanalyse zur Verfügung gestellt.Weissenberg- und Präzessionsdiagramme wurden für eine dreidimensionale Synthese aufgenommen und die Intensität von 81% der gesamten Reflexe gemessen. Die Substanz kristallisiert orthorhombisch. Auf Grund der Reflexauslöschung ist die Raumgruppe P2₁2₁2₁ möglich. Die berechneten Zellkonstanten sowie die berechnete und gemessene Dichte sind in Tab. 1 wiedergegeben.Wegen der kurzen -Achse ist die Aufklärung der Struktur in der Projektion möglich. Da uns die Auflösung derPatterson-Synthese der gleich schweren Atome wegen nicht gelang, wurde eine Permutations-Synthese nachWoolfson mit den sieben stärksten Reflexen durchgeführt. Weiter wurden siebenFourier-Synthesen gemacht und zuletzt einR-Wert 15% erhalten, ohne die Wasserstoffatome zu berücksichtigen. Eine Differenz-Synthese verbesserte denR-Wert nur unwesentlich. Eine weitere Verfeinerung in der Projektion ist wegen der Atomüberlappungen nicht anwendbar. Die relativen Atomkoordinaten sind in der Tab. 2 wiedergegeben.Weitere Strukturuntersuchungen sind noch im Gange.

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Structure of hydrazinium monofluorideShort communication

     

Raman and SERS study of metoclopramide at different pH values

Conjugate acid–base forms of the drug metoclopramide were investigated by Raman spectroscopy in aqueous solutions and by surface‐enhanced Raman scattering (SERS), when the molecules were adsorbed on colloidal silver surfaces. Raman spectra were recorded at pH values below 8, metoclopramide being poorly water soluble at higher pH values. The SERS spectra of metoclopramide were recorded in the 3–11 pH range, even in spite of its low solubility at basic pH values. The Raman and SERS spectra were assigned by means of density functional theory (DFT) calculations. By monitoring several SERS marker bands, the protonated, neutral or the coexistence of both molecular species adsorbed on the colloidal silver particles could be evidenced. The adsorbate orientation was deduced to be perpendicular to the metal surface for the protonated molecular species and tilted for the neutral metoclopramide molecular species. Copyright © 2009 John Wiley & Sons, Ltd.