Strong intramolecular secondary si.N bonds in trifluorosilylhydrazines

The simple silylhydrazines F(3)SiN(Me)NMe(2) (1), F(2)Si(N(Me)NMe(2))(2) (2), and F(3)SiN(SiMe(3))NMe(2) (3) have been prepared by reaction of SiF(4) with LiN(Me)NMe(2) and LiN(SiMe(3))NMe(2), while F(3)SiN(SnMe(3))NMe(2) (4) was prepared from SiF(4) and (Me(3)Sn)(2)NNMe(2) (5). The compounds were characterized by gas-phase IR and multinuclear NMR spectroscopy ((1)H, (13)C, (14/15)N, (19)F, (29)Si, (119)Sn), as well as by mass spectrometry. The crystal structures of compounds 1-5 were determined by X-ray crystallography. The structures of free molecules 1 and 3 were determined by gas-phase electron diffraction. The structures of 1, 2, and 4 were also determined by ab initio calculations at the MP2/6-311+G** level of theory. These structural studies constitute the first experimental proof for the presence of strong Si.N beta-donor-acceptor bonds between the SiF(3) and geminal NMe(2) groups in silylhydrazines. The strength of these non-classical Si.N interactions is strongly dependent on the nature of the substituent at the alpha-nitrogen atom of the SiNN unit, and has the order 3>4>1. The valence angles at these extremely deformed alpha-nitrogen atoms, and the Si.N distances are (crystal/gas): 1 104.2(1)/106.5(4) degrees, 2.438(1)/2.510(6) A; 3 83.6(1)/84.9(4) degrees, 2.102(1)/2.135(9) A; 4 89.6(1) degrees, 2.204(2) A.     

Synthesis and Molecular Structures of Tetrasilyl Ethers of Calix[4]arenes

The tetrasilyl ethers calix[4]areneOSiMe₂R (R = Me, H, vinyl, allyl) were prepared by salt elimination; the calix[4]arene was deprotonated with sodium hydride and subsequently reacted with chlorosilanes ClSiMe₂R. In general, DMF was chosen as solvent in order to steer the reactions in terms of a preference for the cone‐conformation of the products. In the case of calix[4]areneOSiMe₃ both, partial‐cone‐ and cone‐conformers, were synthesised. All products were characterised by NMR (¹H, ¹³C, ²⁹Si) spectroscopy, mass spectrometry and single‐crystal X‐ray diffraction.     

Synthesis and solvent‐dependent micellization of the amphiphilic block copolymer poly(styreneboronic acid)‐block‐polystyrene

The amphiphilic organoboron block copolymer poly (styreneboronic acid)‐block‐polystyrene ( PSBA‐b‐PS ) has been prepared through a postpolymerization modification route from the silicon‐functionalized block copolymer poly(4‐trimethylsilylstyrene)‐block‐polystyrene ( PSSi‐b‐PS ). PSBA‐b‐PS is obtained through highly selective reaction of PSSi‐b‐PS with BBr₃ at room temperature and subsequent hydrolysis of the BBr₂‐functionalized intermediate. Transmission electron microscopy studies demonstrate that PSBA‐b‐PS undergoes pH dependent micellization in aqueous solution. Different morphologies could be realized by using different mixtures of water and organic solvents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2438–2445, 2010     

Donor-substituted peralkynylated "radiaannulenes": novel all-carbon macrocycles with an intense intramolecular charge-transfer

A novel class of planar, highly conjugated all-carbon macrocycles, which we christened "radiaannulenes", have been prepared based on acetylenic scaffolding using tetraethynylethene (TEE) building blocks; these structures are powerful electron acceptors and, upon peripheral substitution with electron-donating N,N-dialkylanilino groups, display intense intramolecular charge-transfer.     

[BuN(CH2CH2)3NBu]3[Pb5I16] · 4 DMF – ein Iodoplumbat mit nahezu D5h‐symmetrischem Anion

[BuN(CH₂CH₂)₃NBu]₃[Pb₅I₁₆] · 4 DMF – an Iodoplumbate Anion with approximately D _5h Symmetry The star‐shaped anion of [BuN(CH₂CH₂)₃NBu]₃‐[Pb₅I₁₆] · 4 DMF ( 1 ) consists of a cyclic arrangement of five PbI₆ octahedra sharing one common I atom in the centre of an almost planar Pb₅ ring. Compound 1 crystallizes in space group P2₁ with a = 1657.2(1), b = 2029.2(1), c = 1773.6(1) pm, β = 113.238(8)°, Z = 2.     

Third Generation ATP Sensor with Enzymatic Analyte Recycling

For the first time the direct electron transfer of an enzyme ‐ cellobiose dehydrogenase, CDH ‐ has been coupled with the hexokinase catalyzed competition for glucose in a sensor for ATP. To enhance the signal output for ATP, pyruvate kinase was coimmobilized to recycle ADP by the phosphoenolpyruvate driven reaction. The new sensor overcomes the limit of 1 : 1 stoichiometry of the sequential or competitive conversion of ATP by effective enzymatic recycling of the analyte. The anodic oxidation of the glucose converting CDH proceeds at electrode potentials below 0 mV vs. Ag|AgCl thus potentially interfering substances like ascorbic acid or catecholamines do not influence the measuring signal. The combination of direct electron transfer of CDH with the enzymatic recycling results in an interference‐free and oxygen‐independent measurement of ATP in the lower µmolar concentration range with a lower limit of detection of 63.3 nM (S/N=3).     

A Borinic Acid Polymer with Fluoride Ion‐ and Thermo‐responsive Properties that are Tunable over a Wide Temperature Range

A new type of smart borinic acid polymer with luminescence and multiple stimuli‐responsive properties is reported. In DMSO with small amounts of water, the homopolymer PBA shows a tunable upper critical solution temperature (UCST). As the amount of water increases from 0 to 2.5 % (v/v), the UCST rises linearly from 20 °C to 100 °C (boiling point of water). Thus, the thermal responsive behavior can be tuned over a wide temperature range. Furthermore, polymer solutions in DMSO show a reversible response to fluoride ions, which can be correlated to the presence of the Lewis acidic borinic acid groups. Upon addition of fluoride, the polymer becomes soluble because the functional R₂BOH groups are converted into ionic [R₂BF₂]^? groups, but turns insoluble again upon addition of H₂O, which reverses this process.     

Mechanism of Host–Guest Complex Formation and Identification of Intermediates through NMR Titration and Diffusion NMR Spectroscopy

The formation of host–guest (H‐G) complexes between 1,8‐bis[(diethylgallanyl)ethynyl]anthracene (H) and the N‐heterocycles pyridine and pyrimidine (G) was studied in solution using a combination of NMR titration and diffusion NMR experiments. For the latter, diffusion coefficients of potential host–guest structures in solution were compared with those of tailor‐made reference compounds of similar shape (synthesized and characterized by NMR, HRMS, and in part XRD). Highly dynamic behavior was observed in both cases, but with different host–guest species and equilibria. With increasing concentrations of the pyridine guest, the equilibrium H₂?H₂κ¹‐G₁?HG₂ is observed (in the second step a host dimer coordinates one guest molecule); for pyrimidine the equilibrium H₂→H₁κ²‐G₁?HG₂ is observed (the formation of a 1:1 aggregate is the second step).