Volume 227, Issue 1 -

Recent technological advances enabled the development of a new broadband Fourier transform microwave spectrometer in 2006. Since then, more than 15 broadband spectrometers have become operational worldwide and have also been extended to the millimeter wave and the terahertz frequency range. In the experiment, the microwave frequency is linearly swept within a short chirp covering up to 12 GHz so far. This chirped pulse efficiently polarizes the molecular sample at all frequencies lying within this frequency range. Fourier transformation of the molecular response from the time domain to the frequency domain gives the broadband rotational spectrum. This new instrument removes one of the major disadvantages of cavity-based Fourier transform microwave spectroscopy, which has been its slowness. As a consequence, rotational spectroscopy is now concentrating on even larger and more complex molecules. Also double-resonance experiments are now facilitated. Furthermore, the broadband technique opens the door towards new directions of rotational spectroscopy, i.e. , towards dynamics studies such as the investigation of isomerization reactions.

The vibrational structures of three paracyclophanes were investigated, ortho -dihydroxy-[2.2]paracyclophane (o-DHPC), mono-hydroxy[2.2]paracyclophane (MHPC) and 2,11-dithia[3.3]paracyclophane (2SPC). Gas-phase infrared spectroscopy helps to identify the most stable isomer of o-DHPC and MHPC in the gas phase, while FT-Raman spectroscopy was used to study S2PC. For o-DHPC the IR spectrum confirms that the EZ -rotamer dominates, while for MHPC the spectra agree better with the Z -rotamer, but are not unambiguous. The Raman spectrum of 2SPC showed a dominance of the trans isomer in the solid state.

Energy decomposition analysis is a powerful tool to study the bond properties of molecules. Here, we used a recent implementation by P. Su and H. Li (J. Chem. Phys. 131 (2009) 014102) to test the method for investigations of ligand binding to medium sized molecules (30–40 atoms). We studied the properties of the bond between porphyrins or phthalocyanines with central metals without (Mg) or with a closed d shell (Zn and Cd) to ligands binding via various row II and III atoms (nitrogen, oxygen, phosphorus and sulphur) using various methods and basis sets. Several interesting results could be deduced: In the porphyrins, ligands binding via a nitrogen atom were preferred to those binding via oxygen and sixfold coordination was readily available for magnesium as central metal atom as opposed to zinc and cadmium derivatives which also showed a weaker bond strength. In phthalocyanines, a tendency to form fivefold coordination was also seen for magnesium compounds and bonds to nitrogen and oxygen had the same strength. Ligation to row III elements created only weak bonds that were prone to fluctuations.

The interference of cyclodextrin solubilization with the measurement of oxygen radical scavenging capacity was investigated. Cyclodextrin (CD) that can solubilize water-insoluble compounds has been used in the oxygen radical scavenging capacity assay called oxygen radical absorbance capacity (ORAC) method. A vitamin E analog, trolox (2-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) has been employed as a standard compound in ORAC methods and the results were often expressed in the trolox equivalent unit. We found that trolox ORAC values measured with electron spin resonance-based ORAC method, were markedly dependent on the CD concentration, i.e. , it decreased by 50% when [CD]/[Trolox] = 100 was present. 2D ROESY NMR study of trolox/CD inclusion complex revealed that trolox resided within the CD cavity. The reactive phenoxyl group in trolox is shielded from the attack by the oxygen radical, suggesting that this hindrance was causal for the decrease in ORAC values.

It is well known that lithium ion batteries degrade due to cycling (cycle life), but also when in standby mode with little or no current throughput (calendar life). Experimental results exist which show the lifetime of a battery under either of these conditions, cycling or standby operation. Results for an application specific mix of cycling and standby operation are, however, not readily available in the scientific literature. The ageing mechanisms of these two modes of operation differ in their impact on capacity and internal resistance as the two most important performance characteristics of a battery. The question is how the ageing mechanisms interact and how certain ageing mechanisms occurring particularly in one mode of operation affect ageing mechanisms which occur predominantly in the other mode of operation. As the conditions of use are very different in terms of current amplitude, state-of-charge and temperature, it is clear that the interaction needs to be considered taking the application into account by using application specific load collectives. This paper will discuss how to approach this problem, shows first results and their relevance for vehicle batteries when used for vehicle to grid operation.

The electrochemical oxidation of nimesulide, a non-steroidal anti-inflammatory drug, was studied in a phosphate medium at a carbon paste electrode under physiological condition. Cyclic voltammetric results showed one well-defined oxidation peak in the potential range from 0.4 to 1.4 V under different pH conditions, but the best results were obtained at pH 7.0. The oxidation process was irreversible and exhibited diffusion-controlled behavior. The response was evaluated with respect to pH and scan rate. The number of electrons transferred in the oxidation process was calculated and the probable oxidation mechanism was proposed. The proposed differential pulse voltammetric method was successfully applied to nimesulide determination in pharmaceutical samples. The analytical performance of this method has been evaluated for detection of analyte in urine as a real sample.

The addition of La 2 O 3 to an aniline polymerizing system to promote the formation of polyaniline nanofibers (PANI-La 2 O 3 ) is herein demonstrated. The fiberization rate is significantly increased by the inducing of La 2 O 3 . Only trace amounts of lanthanum advantageously remain in the product, which therefore negligibly influence the electrochemical characteristics of the resulting polyaniline fibers. Research for the electrochemical reaction kinetics of PANI-La 2 O 3 nanofiber indicates that the redox rate of polyaniline between leucoemeraldine and emeraldine is controlled by electron transfer and proton (H + ) diffusion. The standard rate constants of the redox and the diffusion coefficients of H + are measured at 20 ºC. Cyclic voltammetric (CV) results indicate that PANI-La 2 O 3 nanofibers are resistant against electrochemical degradation. Moreover, the modification of Pt electrode with PANI-La 2 O 3 nanofibers promotes the efficiency of methanol electro-oxidation.

Room temperature ionic liquids (RTILs) are of growing interest due to their outstanding solvent properties. The high conductivity and large electrochemical window of RTILs have enabled their use in electrochemistry without adding supporting electrolyte. Heterogeneous electron transfer rate constants ( k het ) and diffusion coefficients ( D ) of ferrocene, 2,6-dimethylbenzoquinone, bromanil, tetracyanoethylene, tetrathiofulvalene, methylviologen, and ethylviologen were determined in several RTILs such as [emim][BF 4 ], [bmim][OTf], [bmim][BF 4 ] and [bmim][PF 6 ] using cyclic voltammetry. The results obtained for k het and D , range from 0.25–29.6 × 10 4 cm s -1 and 1.27–25.5 × 10 8 cm 2 s -1 respectively. Both were significantly lower than those found in organic solvents like acetonitrile (MeCN), dimethylformamide (DMF), etc. It was found that k het and D were two to three orders of magnitude lower in more viscous RTILs. Diffusion coefficients were inversely proportional to the viscosity of the RTILs for all substances under investigation. Marcus theory was applied to compare the k het . The main problem arising is to understand the role of solvent reorganization energy ( λ o ). Whereas Marcus theory describes λ o in two parts of polarization, a fast electronic and a slower orientational contribution both expressed by the Pekar factor γ = (1/ n 2 - 1/ ɛ s ), the solvent is treated as a continuum having a dielectric constant ( ɛ s ) and a refractive index ( n ). Such a concept seems to be not applicable to ionic liquids.

Two cationic ester-bonded cleavable gemini surfactants of different hydrophobic chain length ethane-1,2-diyl bis( N , N -dimethyl- N -alkylammoniumacetoxy)dichloride, C n H 2 n +1 (CH 3 ) 2 N + (CH 2 COOCH 2 ) 2 N + (CH 3 ) 2 C n H 2 n +1 . 2Cl - ( n -E2- n , n =12, 16), having ester linkage in the spacer, were synthesized adopting the reported procedure. Physicochemical properties of the single and binary gemini-conventional mixed micelles of different mole fractions were studied by conductivity measurements at 30 ºC. The conventional surfactants used were: DTAC (dodecyltrimethylammonium chloride), CTAC (hexadecyltrimethylammonium chloride), CPC (cetylpyridinium chloride), SDS (sodium dodecyl sulfate), SDBS (sodium dodecylbenzene sulfonate), TX-100 ( t -octylphenoxypolyethoxyethanol) and Brij 58 (polyoxyethylene (20) cetyl ether). Whereas the critical micelle concentration ( cmc ) values for the dicationic geminis (12-E2-12 and 16-E2-16) were found to be very low as compared to the respective monomeric surfactant with the same number of carbon atoms in the hydrophobic chain per hydrophilic head group, those for all the binary systems were found to be less than the ideal cmc values studied at different mole fractions of the geminis. This synergistic interaction between the surfactants has been analyzed in the light of various theoretical models such as Clint, Rubingh, Motomura and Maeda.