Simple Synthesis of Ruthenium π Complexes of Aromatic Amino Acids and Small Peptides

The interaction of [Ru(η⁶‐C₁₀H₈)(Cp)]⁺ (Cp=C₅H₅) with aromatic amino acids (L ‐phenylalanine, L ‐tyrosine, L ‐tryptophane, D ‐phenylglycine, and L ‐threo‐3‐phenylserine) under visible‐light irradiation gives the corresponding [Ru(η⁶‐amino acid)(Cp)]⁺ complexes in near‐quantitative yield. The reaction proceeds in air at room temperature in water and tolerates the presence of non‐aromatic amino acids (except those which are sulfur containing), monosaccharides, and nucleotides. The complex [Ru(η⁶‐C₁₀H₈)(Cp)]⁺ was also used for selective labeling of Tyr and Phe residues of small peptides, namely, angiotensin I and II derivatives.     

Ring transformation of 1,5‐diazabicyclo[3.1.0]hexanes under the action of arylketenes

The reactions of 1,5‐diazabicyclo[3.1.0]hexanes 8 with arylketenes 1 have been studied in different conditions. The 1‐(arylacethyl)pyrazolidines 11 were obtained at ?30 °C in ether and at 20 °C in benzene instead of the expected bicyclic systems 1,5‐diazabicyclo[3.2.1]octan‐6‐one 9 and 3‐aryl‐1,5‐diazabicyclo[3.3.0]octane‐2‐one 10 . The synthesis of two representatives of bicycles 10 ( 10a,b ) proceeded in the reaction of unsubstituted 1,5‐diazabicycle[3.1.0]hexane 8a , accordingly, with diphenylketene 1a in benzene at 20 °C and with 4‐chlorophenylketene 1b in toluene at 60‐110 °C. Mechanisms of the studied transformations were offered.     

Complexes of titanium(IV) chloride with N-(3,5-R,R′-salicylidene)-2(3,4)-[bis(5-methyl-2-furyl)methyl]aniline, a novel type of phenoxyimine catalysts for olefin polymerization

New representatives of chelate-type titanium(IV) salicylideneaniline complexes with bis(5-methyl-2-furyl)methyl substituents in the aniline fragment are synthesized. In the presence of poly(methylalumoxane), these complexes catalyze ethylene and propylene polymerization. The effect of the position of substituents in the ligands on the activities of the catalysts is studied. High-molecular-weight linear polyethylene (M _w ≈ 172200–300000, M _w/M _n ≈ 2–3) and high-molecular-weight atactic elastic polypropylene (M _w ≈ 1000000, M _w/M _n ≥ 7.0) are obtained. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1730–1737, October, 2006.     

The "hockey sticks" effect revisited: the conformational and electronic properties of 3,7-dithia-1,5-diazabicyclo[3.3.1]nonane from the QTAIM perspective

The conformational effects in bicyclo[3.3.1]nonanes, while thoroughly studied, have not yet received the full theoretical explanation. R. F. W. Bader's quantum theory of atoms in molecules presents unique opportunities for studying the stereoelectronic interactions (SEI) and weak intramolecular bonding leading to these effects. Here, we report the study of 3,7-dithia-1,5-diazabicyclo[3.3.1]nonane by means of the topological analysis of the calculated (MP2(full)/6-311++G**) and experimental (X-ray derived) charge density to reveal the origins of the so-called "hockey sticks" effect observed in similar compounds. A new explanation of the relative stability of bicyclo[3.3.1]nonane conformers based on the analysis of the QTAIM atomic energies is given. The H···H and S···S interactions in bicyclo[3.3.1]nonane and its dithia derivatives are shown to be significant factors contributing to the differences in the relative stability of the conformers.     

Synthesis and structure of new β-functionalized gem-bromonitroethenes — 2-arylsulfanyl- and 2-aryloxy-3-bromo-3-nitroacrylates

Alkyl 2,3-dibromo-3-nitroacrylates react with arylthiols and phenols to give earlier unknown representatives of β-functionalized gem-bromonitroethenes, namely, 2-arylsulfanyl- and 2-aryloxy-3-bromo-3-nitroacrylates; their structure was characterized by IR, UV, and NMR (¹H, ¹³C{¹H}, HMQC, HMBC) spectroscopy. X-ray diffraction analysis showed that methyl 3-bromo-2-(4-chlorophenylsulfanyl)-3-nitroacrylate has a Z-configuration; the sulfanylbromonitrovinyl fragment in its molecule is relatively coplanar, while the ester group is almost perpendicular to the plane of the C-C double bond.

     

Synthesis,structure, and properties of polynuclear molybdenum(v,vi) oxomethoxides with magnesium

General conditions for the formation of heterometallic clusters by the simultaneous methanolysis of MoCl₅ and MgCl₂ were determined. The resultant alkalinity of the reaction solution, the Mg/Mo molar ratio, and the presence of traces of water are key factors responsible for the composition and structure of the mixed magnesium molybdenum methoxides that formed. The new decanuclear mixed-valence Mo^V,VI Mg oxomethoxide [Mo^V ₄O₄(μ₃-O)₂(μ₂-O)₂Mo^VI ₂-O₄(OMe)₂Mg₄(MeOH)₆(μ₃-OMe)₆(μ₂-OMe)₈] (1) was synthesized by the reaction of lowernuclearity magnesium molybdenum oxoalkoxide complexes: NaMo^V of the complex Na(MeOH)Mo^V ₂O₂(μ₂-OMe)₃(OMe)₄ (2) and MgMo^VI of the complex [Mo^VIO₂Mg(MeOH)₂-(OMe)₄]₂ (3). The molecular structure of 1 was determined by X-ray diffraction.     

Time-resolved and cw photoluminescence from strongly coupled organic microcavities

The optical properties of microcavities (MCs) are strongly dependent on both polarization of incident and emitted light and its angle of observation. Here we report the measurements of cw- and time-resolved photoluminescence (PL) observed at negative detuning and at resonance for s- and p-polarization in the strong coupling regime of a planar MC containing J-aggregates of a cyanine dye. Following non-resonant excitation, the emission spectra consist of three types of features: direct J-aggregate exciton emission, polariton emission, and uncoupled monomer emission through the transmission maxima of the distributed Bragg reflector beyond the stop-band. We compare our experimental results with a transfer-matrix calculation of the transmission for s- and p-polarization and explain the different positions of the polariton branches, the stop-band width, and the high- and low energy transmission maxima of the MC. Time-resolved PL experiments show an increase in the decay lifetime of the exciton-like mode when it is positioned far from the cavity mode. Close to resonance, the lower polariton branch decays with the natural lifetime of the J-aggregates.