Surface‐Guided Formation of an Organocobalt Complex

Organocobalt complexes represent a versatile tool in organic synthesis as they are important intermediates in Pauson–Khand, Friedel–Crafts, and Nicholas reactions. Herein, a single‐molecule‐level investigation addressing the formation of an organocobalt complex at a solid–vacuum interface is reported. Deposition of 4,4′‐(ethyne‐1,2‐diyl)dibenzonitrile and Co atoms on the Ag(111) surface followed by annealing resulted in genuine complexes in which single Co atoms laterally coordinated to two carbonitrile groups undergo organometallic bonding with the internal alkyne moiety of adjacent molecules. Alternative complexation scenarios involving fragmentation of the precursor were ruled out by complementary X‐ray photoelectron spectroscopy. According to density functional theory analysis, the complexation with the alkyne moiety follows the Dewar–Chatt–Duncanson model for a two‐electron‐donor ligand where an alkyne‐to‐Co donation occurs together with a strong metal‐to‐alkyne back‐donation.     

p-Phenyleneethynylene molecular wires: influence of structure on photoinduced electron-transfer properties

A series of donor-acceptor arrays (exTTF-oPPE-C60) containing pi-conjugated oligo(phenyleneethynylene) wires (oPPE) of different length between pi-extended tetrathiafulvalene (exTTF) as electron donor and fullerene (C60) as electron acceptor has been prepared by following a convergent synthesis. The key reaction in these approaches is the bromo-iodo selectivity of the Hagihara-Sonogashira reaction and the deprotecting of acetylenes with different silyl groups to afford the corresponding donor-acceptor conjugates in moderate yields. The electronic interactions between the three electroactive species were determined by using UV-visible spectroscopy and cyclic voltammetry. Our studies clearly confirm that, although the C60 units are connected to the exTTF donor through pi-conjugated oPPE frameworks, no significant electronic interactions are observed in the ground state. Theoretical calculations predict how a simple exchange from C=C double bonds (i.e., oligo(p-phenylenevinylene) to C triple chemical bond C triple bonds (i.e., oPPE) in the electron donor-acceptor conjugates considerably alters long-range electron transfer. Photoexcitation of exTTF-oPPE-C60 leads to the following features: a transient photoproduct with maxima at 660 and 1000 nm, which are unambiguously attributed to the photolytically generated radical-ion-pair state, [exTTF*+-oPPE-C60*]. Both charge-separation and charge-recombination processes give rise to a molecular-wire behaviour of the oPPE moiety with an attenuation factor (beta) of (0.2+/-0.05) A(-1).     

Influence of diamino acid derivatives of protoporphyrin IX on mouse immunological system: preliminary results

Immunological response related to photodynamic therapy (PDT) is one of the basic elements that influence on the efficiency of this cancer treatment method. Diamino acid derivatives of protoporphyrin IX are promising photosensitizing agents that are intended to be the components of new anti-tumor drug. The influence of three derivatives - PP(Ser)(2)Arg(2), PP(Ala)(2)Arg(2), PP(Phe)(2)Arg(2) and a mixture of these compounds called Sensyphyrine on mouse immunological system was investigated where animals were exposed and unexposed to the laser irradiation. Porphyrins solutions were injected intravenously, mice were irradiated with the red diode laser at lambda=632 nm. Cells and blood samples were taken at time intervals after irradiation. The levels of interleukin-6, interleukin-1beta and the production of reactive forms of nitrogen by macrophages were determined. The results show that all of the diamino acid derivatives of protoporphyrin IX indicate an immunological response when the light is applied. Each of the porphyrin revealed different impact on mice immunological system. The most potent stimulant properties disclosed PP(Phe)(2)Arg(2) derivative for which the highest values of IL-1beta, IL-6 and NO(2)(-) were noticed. The weakest immunological activation revealed PP(Ser)(2)Arg(2) derivative.     

Learning from the acquired optimized pulse shapes about the isotope selective ionization of potassium dimers

Selective optimization of the 39,39K2 and 39,41K2 isotopomers in a three-photon ionization process is presented by applying evolution strategies on shaped fs pulses in a feedback loop. The optimizations at different center wavelengths show considerably large enhancements of one isotope compared to the other and reversed. We compare the acquired optimized pulse shapes for combined phase and amplitude with pure amplitude modulation. Particularly from their spectra we are able to extract information about the optimally chosen differing ionization paths via the involved vibrational states. Furthermore, a comparison of the temporal shape of the optimized pulse forms for combined phase and amplitude with pure phase optimization is given. The presented pulse form analysis demonstrates the potential of restricted optimization to gain insight into the underlying dynamical processes. Our approach reveals how the optimization algorithm precisely addresses the vibrational wave functions both spectrally and temporally.     

Ground‐State Structure of the Proton‐Bound Formate Dimer by Cold‐Ion Infrared Action Spectroscopy

The proton‐bound dicarboxylate motif, RCOO^??H⁺?^?OOCR, is a prevalent chemical configuration found in many condensed‐phase systems. The proton‐bound formate dimer HCOO^??H⁺?^?OOCH was studied utilizing cold‐ion IR action spectroscopy in the range 400–1800 cm^?1. The spectrum obtained at ca. 0.4 K of ions captured in He nanodroplets was compared to that measured at ca. 10 K by photodissociation of Ar‐ion complexes. Similar band patterns are obtained by the two techniques that are consistent with calculations for a C₂ symmetry structure with a proton shared equally between the two formate moieties. Isotopic substitution experiments point to the nominal parallel stretch of the bridging proton appearing as a sharp, dominant feature near 600 cm^?1. Multidimensional anharmonic calculations reveal that the bridging proton motion is strongly coupled to the flanking ?COO^? framework, an effect that is in line with the expected change in ?C=O bond rehybridization upon protonation.     

Have photosynthetic pigments been formulated for chemical stability? A cursory insight into the reactivity of magnesium porphyrinoids

Abstract

Magnesium complexes with reduced tetrapyrrolic ligands are active compounds of plant and bacteria photosystems. However, also the porphyrin complex appears as an intermediate on the biosynthetic pathway of the photosynthetic pigments. Its transformations, in particular the reduction of pyrrole rings, lead to the acquisition of the properties that are primary for activity in antenna systems and reaction centers. On the other hand, modifications of the porphyrin system must affect the resistance to destructive processes, such as loss of metal ion and its substitution. In order to compare the stability of three natural Mg complexes, namely Mg protoporphyrin IX, chlorophyll a, and bacteriochlorophyll a, spectroscopic studies in solution were performed. The difference in the electronic structure of the macrocyclic ligand was the basic variable in testing the action against d-electron metal salts and acetic acid. The spectroscopic studies were supplemented with calculations using the Density Functional Theory which provided insight into the stability of M(II)-N bonds depending on the dimension of the delocalized electron system. The results indicate the decreasing stability of Mg(II) complexes on the biosynthetic pathway, thereby providing an additional justification for incorporation of the metal ion into porphyrin prior to the electronic modifications of the tetrapyrrolic system.     

NMR spectra of chiral smectic liquid crystals differing in helical parameters

Chiral liquid crystals with three-ring rigid core were examined. The method based on the selectively reflected light was used to determine the helical pitch. The helical twist sense was worked out using the polarimetry method. ¹H and ¹³C NMR measurements were performed. The influence of three molecular structure parameters: the type of chiral centre, the length of non-chiral chain and substitution of benzene ring by fluorine atoms, on helical pitch, handedness of helical structure and values of chemical shift in proton and carbon spectra was determined. The change of the length of non-chiral terminal chain has the most significant influence on the temperature dependence of helical pitch. All tested parameters have the biggest influence on the values of chemical shift of atoms in the chiral centre.     

Refractive index matched liquid crystal cell for laser metrology application

There exists a problem in advanced numerically controlled automatic laser metrology. Reported study is related to minimising the system generating three or more coherent laser measuring beams. These rays, generated in a proper rangefinder, are necessary to determine the spatial coordinates and spatial orientation of the measured details. The simplest solution is to generate laser coherent light beams of wavelength λ = 0.6328 µm with a given light polarisation plane and then to direct them along three or more independent optical paths. To form these optical paths, a special refractive index matched liquid crystal cell (MLCC) might be applied. To ensure a stable laser operation during the measurement process, the back reflection of the laser beam from MLCC should not exceed 0.7%. The main task of this work is developing such a MLCC transducer. To reach the critical back reflection low enough, the MLCC is constructed as multilayer structure. MLCC operates in positive twisted nematic (TN) mode. Owing to the high-birefringence nematic liquid crystal mixture used and rather big cell gap, the elaborated low reflective MLCC (with R < 0.7%) works at TN mode above the sixth interference maximum of transmitting linearly polarised light.     

Development of Adenosine Deaminase-Specific IgY Antibodies: Diagnostic and Inhibitory Application

Adenosine deaminase (ADA) is currently used as a diagnostic marker for tuberculous pleuritis. Although ADA has been suggested as a potential marker for several types of cancer, the importance of each of ADA isoforms as well as their levels and enzymatic activities in tumors need to be further investigated. Herein we developed avian immunoglobulin Y highly specific to human ADA via hens immunization with calf adenosine deaminase. The obtained antibodies were used for the development of a sensitive double-egg yolk immunoglobulin (IgY) sandwich ELISA assay with an ADA detection limit of 0.5 ng/ml and a linearity range of up to 10 ng/ml. Specific, affinity-purified IgYs were able to recognize human recombinant ADA and ADA present in human cancer cell lines. In addition, antigen-specific IgY antibodies were able to inhibit catalytic activity of calf ADA with an IC₅₀ value of 47.48 nM. We showed that generated IgY antibodies may be useful for ADA detection, thus acting as a diagnostic agent in immunoenzymatic assays.     

Impact of Ionic Strength of Carrier Liquid on Recovery in Flow Field-Flow Fractionation

Asymmetrical flow field-flow fractionation (AF4) and hollow-fiber flow field-flow fractionation (HF5) are techniques widely used in analytical, industrial and biological analyses. The main problem in all AF4 and HF5 analyses is sample loss due to analyte–membrane interactions. In this work the impact of liquid carrier composition on latex nanoparticles (NPs) separation in water and two different concentrations of NH₄NO₃ was studied. In AF4, a constant trend of decreasing the size of 60 and 121.9 nm particles induced by the ionic strength of the carrier liquid has been observed. In contrast, an agglomeration effect of the biggest 356 nm particles was observed when increasing ionic strength, which induced a significant drop of recovery to 35%. H5F provides better resolution and intensified peaks of NPs, but careful optimisation of system parameters is mandatory to obtain good separation.