Preparation of polyetherol-appended sulfur porphyrazines and investigations of peripheral metal ion binding in polar solvents

We describe the complete synthesis and characterization of a new family of peripherally functionalized porphyrazines (pz's) with four, three, or two (in a trans conformation) bis[thioethoxy(ethoxy)ethanol] moieties appended at the pyrroles. These "polyetherol" groups serve as weak exocyclic binding sites for a number of metal ions and also provide solubility of the pz's in low molecular-weight alcohols and water. Electronic spectra of the modified porphyrazines exhibit distinct changes in the visible region (both absorbance and fluorescence) in response to treatment with Ag+, Pb2+, Cd2+, Cs+, and Ni2+ in solution. Such properties make these compounds intriguing candidates for incorporation into the transducer layers in optically based chemical sensors.     

Muon bundles produced by UHE cosmic rays at large zenith angles

The first experimental results on a new EAS observable, the local muon density spectra measured with a large area coordinate detector DECOR in a wide range of zenith angles, are presented. These data correspond to the interval of primary particle energies from 10¹⁵ to 10¹⁸ eV. Some features of local muon density phenomenology are considered on the basis of an analytical model. Expected distributions of the events in the muon density have been calculated by means of the CORSIKA code and compared with experimental data. The text was submitted by the authors in English.     

Muon diagnostics: Present status

Muon diagnostics is a technique for the remote monitoring of various dynamic processes in the heliosphere and the Earth’s magnetosphere and atmosphere, based on analyzing spatial and angular variations in the flux of muons detected simultaneously from all directions in the upper hemisphere. Approaches to data analysis and some of the results of studies of the atmospheric and extra-atmospheric processes detected using the URAGAN muon hodoscope are discussed.     

Closed inflationary universe in patch cosmology

In this paper, we study closed inflationary universe models using the Gauss–Bonnet Brane. We determine and characterize the existence of a universe with Ω>1, with an appropriate period of inflation. We have found that this model is less restrictive in comparison with the standard approach where a scalar field is considered. We use recent astronomical observations to constrain the parameters appearing in the model.     

Evaluation of the adsorption free energy of light guest molecules in nanoporous host structures

We present a simple method for estimation of the adsorption free energy of lightweight featureless molecules in nanoporous structures. The partition function of the system is computed quantum mechanically within the ideal gas approximation, and leads directly to the free adsorption energy. Storage capacities can be estimated by combining the ideal gas results with the real gas equation of state. Two possible implementations of the approach are discussed. The assumptions and potential sources of errors in the calculations are analyzed. The performance of the method is illustrated for graphitic slit pores and solid C60.     

Theoretical analysis of spin crossover in iron(II) [2×2] molecular grids

We use quantum-chemical density functional theory calculations to elucidate the origin of spin-crossover pathways in two iron(II) [2×2] molecular grids with carbohydrazide-based bridging ligands. The complexes are characterized energetically and structurally in five available spin states. Special attention is paid to analysis of the structural distortion induced on each iron center by spin transition on any of its neighbors. The evolution of coordination polyhedra is monitored using the Continuous Shape Measures. It is demonstrated that a succession of spin transitions on different centers depends on the character of the induced distortion, either approaching or getting them away from a more regular low-spin geometry. These effects, resulting from the elasticity of bridging ligands, can be modulated by weak perturbations such as a change of the positions of the hydrogen atoms.     

Determination of cobalt in water samples by photoacoustic spectroscopy with a solid-phase spectrophotometry approach using 3-(2-pyridyl)-5,6-bis(4-sulfophenyl)-1,2,4-triazine

This work forms part of an investigation which seeks to determine metal complexes in a solid phase by photoacoustic spectrometry (PAS). Results of spectral determination of Co(II) complexes are introduced. The method is based on Co(II) colorimetric reaction with 3-(2-pyridyl)-5,6-bis(4-sulfophenyl)-1,2,4-triazine (FST, ferrozine) retained on an anion-exchange resin, DEAE Sephadex A-25. The immobilization of Co(II) on the solid phase is combined with PAS measurement. A numerical approach is applied to reduce noise in the spectral data. At λ = 477 nm, the calibration for Co(II) is linear over the range 14–300 μgL^{− 1}. The Co(II) concentration in water samples was determined by conventional photoacoustic measurement. The relative standard deviation (R.S.D.) of the method for the calibration is < 5%. Under optimized conditions, the obtained analytical features were LOD 14 μgL^{− 1} and LOQ 45 μgL^{− 1}.     

Novel protection-deprotection strategies in diazeniumdiolate chemistry: synthesis of V-IPA/NO

Synthesis of previously inaccessible, potentially liver selective HNO donor V-IPA/NO ([iPrHN(3)-N(1)(O(1))=N(2)-O(2)-R], where R = vinyl) is reported here. A novel fluoride-labile TOM group at O-2 in conjunction with MOM protection at N-3 in IPA/NO is employed. The strategy developed is also extended to synthesis of other NO-releasing prodrugs and has applications in diversity-oriented synthesis of HNO- and NO-prodrugs.     

Koordinationspolymere aus Metallotripyrrinen

Coordination Polymers from Metal Tripyrrins This Research Report summarizes recent advances in the coordination chemistry of tripyrrins and related ligands with a special emphasis on the structural chemistry of coordination polymers with such ligands. The tripyrrin ligand is unique in supporting the formation of 1D‐ and 3D supramolecular structures from pentacoordinate transition metal ions due to an effective blockage of their sixths coordination site. Linear coordination polymers have been observed with a multitude of bidentate and tridentate bridging ligands like trifluoroacetate, azide, thio‐ and selenocyanate, and higher order pseudohalides. Homo‐ and heterodimetallic species have been obtained by the use of cyanometallates and could be characterized structurally in two cases. Besides the covalent coordination bonds several secondary interactions like hydrogen bonding and π‐stacking were found to support these coordination polymers and are demonstrated to allow the preparation of species with functionalized inner surfaces.