Nanodroplet Cluster Formation in Ionic Liquid Microemulsions

A common ionic liquid (IL), 1‐butyl‐3‐methylimidazolium tetrafluoroborate (bmimBF₄), is used as polar solvent to induce the formation of a reverse bmimBF₄‐in‐toluene IL microemulsion with the aid of the nonionic surfactant Triton X‐100. The swelling process of the microemulsion droplets by increasing bmimBF₄ content is detected by dynamic light scattering (DLS), conductivity, UV/Vis spectroscopy, and freeze‐fracture transmission electron microscopy (FF–TEM). The results show that the microemulsion droplets initially formed are enlarged by the addition of bmimBF₄. However, successive addition of bmimBF₄ lead to the appearance of large‐sized microemulsion droplet clusters (200–400 nm). NMR spectroscopic analysis reveal that the special structures and properties of bmimBF₄ and Triton X‐100 together with the polar nature of toluene contribute to the formation of such self‐assemblies. These unique self‐assembled structures of IL‐based microemulsion droplet clusters may have some unusual and unique properties with a number of interesting possibilities for potential applications.     

Evidence for Non-Innocence of a β-Diketonate Ligand

β-Diketonates, such as acetylacetonate, are amongst the most common bidentate ligands towards elements across the entire periodic table and are considered wholly redox-inactive in their complexes. Herein we show that complexation of 1,1,1,5,5,5-hexafluoroacetylacetonate (hfac⁻) to Cr^II spontaneously affords Cr^III and a reduced β-diketonate radical ligand scaffold, as evidenced by crystallographic analysis, magnetic measurements, optical spectroscopy, reactivity studies, and DFT calculations. The possibility of harnessing β-diketonates as electron reservoirs opens up possibilities for new metal–ligand concerted reactivity in the ubiquitous β-diketonate coordination chemistry.     

NONLINEAR LASERSPECTROSCOPIC INVESTIGATIONS OF THE PIGMENT-PIGMENT INTERACTION WITHIN THE LIGHT-HARVESTING COMPLEX OF PHOTOSYSTEM II

Using a pump and test beam technique in the frequency domain with pump pulses in the nanosecond time range, the nonlinear transmission properties were investigated at room temperature in photosystem (PS) II membrane fragments and isolated light-harvesting chlorophyll a/b-protein preparations (LHC II preparations). In LHC II preparations and PS II membrane fragments, respectively, pump pulses of 620 nm and 647 nm cause a transmission decrease limited to a wavelength region in the nearest vicinity of the pump pulse wavelength (full width at half maximum ' 0.24 nm). In contrast, at 670 nm neither a transmission decrease nor a narrow band feature were observed. The data obtained for PS II membrane fragments and LHC II preparations at shorter wavelengths (620 nm, 647 nm) were interpreted in terms of excited state absorption of whole pigment-protein clusters within the light-harvesting antenna of photosystem II. The interpretation of the small transmission changes as homogeneously broadened lines led to a transversal relaxation time for chlorophyll in the clusters of about 4 ps.     

Nuclear magnetic relaxation in water revisited

In this study, we revisited nuclear magnetic relaxation of (1)H in water at very low Larmor frequencies that has been studied intensively in earlier years. We make use of the recently developed superconducting quantum interference device based ultra-low field NMR technique, which enables much easier access to the longitudinal spin-lattice relaxation time T(1) and the transversal spin-spin relaxation time T(2) below several kHz than traditional field cycling methods. Our data reproduce and complement the earlier results, in that they corroborate the finding of an exchange process with a correlation time of about 0.34 ms at room temperature which can be attributed to the migration of hydronium and hydroxyl ions in neutral water via hydrogen bridges. The corresponding relaxation process is driven by the interaction of the protons with (17)O and contributes to the T(1) and the T(2) relaxation rate by about 0.12 s(-1). In addition, we found evidence of a very slow exchange process at about 100 Hz that has hitherto not been reported.     

N‐Heterocyclic Silylenes in Boron Chemistry: Facile Formation of Silylboranes and Silaborinines

Reaction of a N‐heterocyclic silylene (NHSi) with PhBX₂ (X=Cl, Br) readily afforded six‐membered silaborinines through an insertion/ring expansion sequence. Increasing the sterics of the borane from phenyl to duryl enabled the selective generation and isolation of the highly colored silylborane intermediates. Theoretical studies on the mechanism and energetics of the silaborinine formation were fully consistent with the experimental observations.     

The structure of [M(H2O)6][LiFeIII(ox)3] (M=MnII,FeII) – A heterobimetallic 2-D tris(oxalato) framework compound

[Mn^II_xFe^II_1?x(H₂O)₆][LiFe^III(ox)₃] (with 0 ≤ x ≤ 1) crystallizes in the space group P31c with a = 9.341(3) Å, c = 10.226(3) Å, c/a = 1.0947, and V = 772.8(5) Å³ for Z = 2. The compound has a layered structure with two enantiomeric layers per unit cell. The layers are built up by an iron and lithium oxalate framework with intercalated M(II)-water octahedra of the formula [Mn^II_xFe^II_1?x(H₂O)₆][M^IM^III(ox)₃]. The value of x cannot be specified at present. The structure displays intermolecular hydrogen bonding between the layers.     

The behaviour of cellulose in hydrated melts of the composition LiXċn H2O (X=I−, NO3−, CH3COO−, ClO4−)

The dissolution behaviour of cellulose in low temperature molten salts was investigated. Depending on the chosen anions in the melt, cellulose shows different reaction behaviour in different Li⁺containing melts. Dissolution of the polymer was observed in molten LiClO₄3H₂O and molten LiI2H₂O. In the hydrated melts of LiCH₃COO2H₂O and LiNO₃3H₂O a fine distribution of cellulose was stated. Cellulose can be regenerated by cooling the melt and removing the salt by dissolution in water.The structure of the recrystallized product is determined by the used low temperature molten salt.