IR,Raman, and UV/Vis Spectra of Corannulene for Use in Possible Interstellar Identification

The spectroscopic characterization of corannulene (C₂₀H₁₀) is carried out by several techniques. The high purity of the material synthesized for this study was confirmed by gas chromatography‐mass spectrometry (GC‐MS). During a high‐performance liquid chromatography (HPLC) process, the absorption spectrum of corannulene in the ultraviolet (UV) and visible (vis) ranges is obtained. The infrared (IR) absorption spectrum is measured in CsI pellets, and the Raman scattering spectrum is recorded for pure crystal grains. In addition to room temperature measurements, absorption spectroscopy in an argon matrix at 12 K is also performed in the IR and UV/Vis ranges. The experimental spectra are compared with theoretical Raman and IR spectra and with calculated electronic transitions. All calculations are based on the density functional theory (DFT), either normal or time‐dependent (TDDFT). Our results are discussed in view of their possible application in the search for corannulene in the interstellar medium.     

Platinum species in the pores of NaX, NaY and NaA zeolites studied using EPR, XAS and FTIR spectroscopies

The results of X-band EPR, X-ray absorption and Fourier transform infrared spectroscopy on Pt(NH(3))(4)(2+) exchanged NaX, NaY and NaA zeolites reveal after oxygen calcination at 573 K that diamagnetic Pt(2+) is not the only product. Calcination provides Pt(3+) cations, but depending on the heating rate, the decomposition of amino groups during calcination also produces hydrogen that reduces Pt(3+) to Pt(2+) and Pt(+). NaX (Si/Al = 1.23) has a more negative framework charge than NaY (Si/Al = 2.31), so Pt(3+) can be stabilized only in NaX, whereas lower oxidation states of Pt such as Pt(+) can be stabilized in both, NaX and NaY, and neither of the paramagnetic Pt cations are stabilized in NaUSY (Si/Al = 3). The autoreduction process allows controlling the number of Pt(3+) and Pt(+) in the NaX zeolite by changing the calcination heating rate: a heating rate of 1.25 K min(-1) gives only Pt(+), but 0.5 K min(-1) gives a Pt(3+)/Pt(+) ratio close to 1. The structure of the support is also important for the synthesis of Pt species. While isolated paramagnetic Pt ions were stabilized in faujasite zeolites (NaX and NaY), a paramagnetic Pt dimer was obtained in a Linde type A zeolite (LTA, Si/Al = 1) by applying the same preparation methods. The fraction of paramagnetic Pt species which were characterized by X-band EPR spectroscopy amounts to 2-18% of the total Pt in the zeolites, the remaining Pt must be diamagnetic.     

Direct detection of formaldehyde in air by a novel NAD+- and glutathione-independent formaldehyde dehydrogenase-based biosensor

An amperometric enzyme-based sensor-system for the direct detection of formaldehyde in air is under investigation. The biosensor is based on a native bacterial NAD(+)- and glutathione-independent formaldehyde dehydrogenase as biorecognition element. The enzyme was isolated from Hyphomicrobium zavarzinii strain ZV 580, grown on methylamine hydrochloride in a fed-batch process. The sensor depends on the enzymatic conversion of the analyte to formic acid. Released electrons are detected in an amperometric measurement at 0.2V vs. Ag/AgCl reference electrode by means of a redox-mediator. To optimize the sensing device, Ca(2+) and pyrroloquinoline quinone (PQQ) were added to the buffer solution as reconstitutional substances. At this stage, the sensor shows linear response in the tested ppm-range with a sensitivity of 0.39 microA/ppm. The signal is highly reproducible with respect to sensitivity and base line signal. Reproducibility of sensitivity is more than 90% within the same bacterial batch and even when enzyme of different bacterial batches is used.     

Isomerization in bent phosphametallocenes: Combining rotational barriers and the intramolecular slip-inversion-slip mechanism to control stereo-conformation

Four new phosphazirconocenes, [(4,5,6-trihydro-1-phosphapentalenyl)₂ZrCl₂] (8), [(4,5,6,7-tetrahydro-1-phosphindolyl)₂ZrCl₂] (9), [(4,5,6,7,8-pentahydro-1-phosphazulenyl)₂ZrCl₂] (10), (2,4-dimethylphospholyl)₂ZrCl₂ (11), were prepared and characterized. A crystal structure of [(4,5,6,7-tetrahydro-1-phosphindolyl)₂ZrCl₂] (9), was obtained that revealed disorder (rac and meso isomers in the same crystal) and demonstrates unambiguously the meso configuration in the bent early transition metal phosphametallocenes. Lacking a spectroscopic probe of the rotational dynamics in phosphametallocenes, propylene polymerization was chosen to provide a record of the stereoselective insertions and by inference insight into the phosphametallocene dynamics. Phosphazirconocenes 8-11 were evaluated, and the rac/meso mixture of [(4,5,6,7-tetrahydro-1-phosphindolyl)₂ZrCl₂] (9) was found to produce a mixture of isotactic (iPP) and atactic (aPP) polypropylenes. ¹³C NMR spectral analysis of the stereo-errors contained in the iPP fraction indicated enantiomorphic site control as the source of the stereoselectivity. The rotational dynamics of the η⁵-phospholyl ligand of the parent phosphazirconocene, [(C₄H₄P)₂ZrCl₂], was examined as a first order surrogate of reasonable computing complexity for the catalytically active species. The phosphazirconocene was examined using a restricted Hartree-Fock method with a split basis set of 6-311+G(d,p) for C, H, Cl, P and of LANL2DZ for Zr. The rotational potential energy surface was found to be unsymmetrical with a maximum barrier of 8.8 kcal mol⁻¹, which is about an order of magnitude greater than that reported for Cp₂ZrCl₂. The projection of the calculated rotational dynamics onto a 1-phosphatetrahydroindenyl system is illustrated. This model leads to an interpretation of the polymerization results and the rotational dynamics in phosphametallocenes.     

An interlaboratory capillary zone electrophoresis-UV study of various monoclonal antibodies,instruments, and ε-aminocaproic acid lots

Capillary zone electrophoresis ultraviolet (CZE-UV) has become increasingly popular for the charge heterogeneity determination of mAbs and vaccines. The ε-aminocaproic acid (eACA) CZE-UV method has been used as a rapid platform method. However, in the last years, several issues have been observed, for example, loss in electrophoretic resolution or baseline drifts. Evaluating the role of eACA on the reported issues, various laboratories were requested to provide their routinely used eACA CZE-UV methods, and background electrolyte compositions. Although every laboratory claimed to use the He et al. eACA CZE-UV method, most methods actually deviate from He's. Subsequently, a detailed interlaboratory study was designed wherein two commercially available mAbs (Waters’ Mass Check Standard mAb [pI 7] and NISTmAb [pI 9]) were provided to each laboratory, along with two detailed eACA CZE-UV protocols for a short-end, high-speed, and a long-end, high-resolution method. Ten laboratories participated each using their own instruments, and commodities, showing excellence method performance (relative standard deviations [RSDs] of percent time-corrected main peak areas from 0.2% to 1.9%, and RSDs of migration times from 0.7% to 1.8% [n = 50 per laboratory], analysis times in some cases as short as 2.5 min). This study clarified that eACA is not the main reason for the abovementioned variations.     

Method development for quantitative monitoring of monoclonal antibodies in upstream cell-culture process samples with limited sample preparation – An evaluation of various capillary coatings

Monoclonal antibodies (mAbs) have become an important class of biopharmaceuticals used for the treatment of various diseases. Their quantification during the manufacturing process is important. In this work, a capillary zone electrophoresis (CZE) method was developed for the monitoring of the mAb concentration during cell-culture processes. CZE method development rules are outlined, particularly discussing various capillary coatings, such as a neutral covalent polyvinyl alcohol coating, a dynamic successive multiple ionic-polymer coating, and dynamic coatings using background electrolyte additives such as triethanolamine (T-EthA) and triethylamine. The dynamic T-EthA coating resulted in most stable electro-osmotic flows and most efficient peak shapes. The method is validated over the range 0.1–10 mg/ml, with a linear range of 0.08–1.3 mg/ml and an extended range of 1–10 mg/ml by diluting samples in the latter concentration range 10-fold in water. The intraday precision and accuracy were 2%–12% and 88%–107%, respectively, and inter-day precision and accuracy were 4%–9% and 93%–104%, respectively. The precision and accuracy of the lowest concentration level (0.08 mg/ml) were slightly worse and still well in scope for monitoring purposes. The presented method proved applicable for analysing in-process cell-culture samples from different cell-culture processes and is possibly well suited as platform method.     

Categories with homotopy determine a closed model structure

In a category with homotopy (Definition 1.1), one can define a natural concept of (co)fibrations and weak equivalences (Sec. 2) such that some properties of a closed model category hold. If is a complete and cocomplete category (with respect to finite limits) with simplicial homotopy (Definition 1.3), one achieves a full closed model structure in (Theorem 4.6). For each category with homotopy , there exists a category with simplicial homotopy (see Sec. 5) (the simplicial envelope of ). If is already a complete category with simplicial homotopy, then is Quillen equivalent to (Theorem 5.9). __________ Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 41, Topology and Its Applications, 2006.     

The elusive structure of CrCl(2): a combined computational and gas-phase electron-diffraction study

Chromium dichloride poses a challenge to the structural chemist. Its different forms of aggregation and association display all well-known structural distortions induced by vibronic interactions. The monomeric molecule has a Renner-Teller distorted bent geometry, the crystal exhibits strong Jahn-Teller distortion, and the oligomers have slightly distorted four-membered-ring structures due to the pseudo-Jahn-Teller effect. In this paper we report on the low-energy structures of the monomer and its clusters, Cr(2)Cl(4), Cr(3)Cl(6), and Cr(4)Cl(8), from unrestricted Kohn-Sham (broken-symmetry) density functional calculations. CrCl(2) was also investigated at higher level, including coupled-cluster and state-average CASSCF computations. The global minima of the gas-phase clusters consist of two-dimensional, antiferromagnetically coupled chains of CrCl(2) units forming four-membered, doubly bridged Cr(2)Cl(2) rings, closely resembling the solid-state structure of alpha-CrCl(2). Each Cr atom in these chains has spin quantum number S=2. This suggests that the CrCl(2) nucleation starts very early on the structural chain motif found in the solid. There is only a very small change in energy from the antiferromagnetically to the ferromagnetically coupled Cr atoms, which indicates little spin-coupling between the metal centers. There is an approximately constant change in energy, about 50 kcal mol(-1), with every new CrCl(2) unit during cluster formation. Information about the structure of these clusters was used in the re-analysis of high-temperature electron-diffraction data. The vapor at 1170 K contained about 77 % monomeric molecules, 19 % dimers, and a small amount of trimers. Monomeric CrCl(2) was found to be bent with a bond angle of 149(10) degrees, in good agreement with our computations, which resulted in a Renner-Teller distortion of the lowest-energy (5)Pi(g) electronic state into the bent (5)B(2) ground state. The vibrational spectrum of chromium dichloride is discussed and the thermodynamics of cluster formation from 1000-2000 K is examined.     

Coordination chemistry of the cyclo-(P(5)tBu(4))(-) ion: monomeric and oligomeric copper(I), silver(I) and gold(I) complexes

[Na{cyclo-(P(5)tBu(4))}] (1) reacts with [CuCl(PCyp(3))(2)] (Cyp=cyclo-C(5)H(9)) and [CuCl(PPh(3))(3)] (1:1) to give the corresponding copper(I) complexes with a tetra-tert-butylcyclopentaphosphanide ligand, [Cu{cyclo- (P(5)tBu(4))}(PCyp(3))(2)] (2) and [Cu{cyclo-(P(5)tBu(4))}(PPh(3))(2)] (3). The CuCl adduct of 2, [Cu(2)(mu-Cl){cyclo-(P(5)tBu(4))}(PCyp(3))(2)] (4), was obtained from the reaction of 1 with [CuCl(PCyp(3))(2)] (1:2). Compounds 2 and 3 rearrange, even at -27 degrees C, to give [Cu(4){cyclo- (P(4)tBu(3))PtBu}(4)] (5), in which ring contraction of the [cyclo-(P(5)tBu(4))](-) anion has occurred. The reaction of 1 with [AgCl(PCyp(3))](4) or [AgCl(PPh(3))(2)] (1:1) leads to the formation of [Ag(4){cyclo-(P(4)tBu(3))PtBu}(4)] (6). Intermediates, which are most probably mononuclear, "[Ag{cyclo-(P(5)tBu(4))}(PR(3))(2)]" (R=Cyp, Ph) could be detected in the reaction mixtures, but not isolated. Finally, the reaction of 1 with [AuCl(PCyp(3))] (1:1) yielded [Au{cyclo-(P(5)tBu(4))}(PCyp(3))] (7), whereas an inseparable mixture of [Au(3){cyclo-(P(5)tBu(4))}(3)] (8) and [Au(4){cyclo-(P(4)tBu(3))PtBu}(4)] (9) was obtained from the analogous reaction with [AuCl(PPh(3))]. Complexes 3-7 were characterised by (31)P NMR spectroscopy, and X-ray crystal structures were determined for 3-9.