Dissociative electron attachment and electronic excitation in Fe(CO)5.

In a combined experimental and theoretical study we characterize dissociative electron attachment (DEA) to, and electronically excited states of, Fe(CO)5. Both are relevant for electron-induced degradation of Fe(CO)5. The strongest DEA channel is cleavage of one metal-ligand bond that leads to production of Fe(CO)4-. High-resolution spectra of Fe(CO)4- reveal fine structures at the onset of vibrational excitation channels. Effective range R-matrix theory successfully reproduces these structures as well as the dramatic rise of the cross section at very low energies and reveals that virtual state scattering dominates low-energy DEA in Fe(CO)5 and that intramolecular vibrational redistribution (IVR) plays an essential role. The virtual state hypothesis receives further experimental support from the rapid rise of the elastic cross section at very low energies and intense threshold peaks in vibrational excitation cross sections. The IVR hypothesis is confirmed by our measurements of kinetic energy distributions of the fragment ions, which are narrow (∼0.06 eV) and peak at low energies (∼0.025 eV), indicating substantial vibrational excitation in the Fe(CO)4- fragment. Rapid IVR is also revealed by the yield of thermal electrons, observed in two-dimensional (2D) electron energy loss spectroscopy. We further measured mass-resolved DEA spectra at higher energies, up to 12 eV, and compared the bands observed there to resonances revealed by the spectra of vibrational excitation cross sections. Dipole-allowed and dipole/spin forbidden electronic transitions in Fe(CO)5-relevant for neutral dissociation by electron impact-are probed using electron energy loss spectroscopy and time-dependent density functional theory calculations. Very good agreement between theory and experiment is obtained, permitting assignment of the observed bands.

Resolving the origin of the multimode Jahn-Teller effect in metallophthalocyanines.

A detailed Density Functional Theory (DFT) analysis was performed in order to study the multimode Jahn-Teller (JT) problem in the electronic ground state of manganese phthalocyanine (MnPc). A comparison with the magnesium phthalocyanine ion (MgPc-) and the phthalocyanine trianion (Pc3-), also prone to the JT effect, is presented. Our results clarify the origin and provide the microscopic insight into the symmetry breaking process. The JT distortion is highly influenced by the coordination of phthalocyanine to the MnII ion, and occurs over the whole system, while the MgPc- complex ion possesses mainly ligand-based instability.

Quantitative structure-activity relationship analysis of substituted arylazo pyridone dyes in photocatalytic system: Experimental and theoretical study.

A series of arylazo pyridone dyes was synthesized by changing the type of the substituent group in the diazo moiety, ranging from strong electron-donating to strong electron-withdrawing groups. The structural and electronic properties of the investigated dyes was calculated at the M062X/6-31+G(d,p) level of theory. The observed good linear correlations between atomic charges and Hammett σp constants provided a basis to discuss the transmission of electronic substituent effects through a dye framework. The reactivity of synthesized dyes was tested through their decolorization efficiency in TiO2 photocatalytic system (Degussa P-25). Quantitative structure-activity relationship analysis revealed a strong correlation between reactivity of investigated dyes and Hammett substituent constants. The reaction was facilitated by electron-withdrawing groups, and retarded by electron-donating ones. Quantum mechanical calculations was used in order to describe the mechanism of the photocatalytic oxidation reactions of investigated dyes and interpret their reactivities within the framework of the Density Functional Theory (DFT). According to DFT based reactivity descriptors, i.e. Fukui functions and local softness, the active site moves from azo nitrogen atom linked to benzene ring to pyridone carbon atom linked to azo bond, going from dyes with electron-donating groups to dyes with electron-withdrawing groups.

Spectroscopic and quantum chemical investigations of substituent effects on the azo-hydrazone tautomerism and acid-base properties of arylazo pyridone dyes.

A series of 5-(4-substituted arylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridone dyes was synthesized and the structure of the dyes was confirmed by UV-Vis, FT-IR, (1)H NMR and (13)C NMR spectroscopic techniques. The azo-hydrazone tautomeric equilibrium was found to depend on the substituents as well as on the acidity and basicity of the media. Ionization constant, pKa, of the dyes was determined by UV-Vis spectroscopy and correlated with the Hammett substituent constants, σp and σI. The interpretation of the effect of different substituent in phenyl ring of arylazo pyridone dyes on their spectroscopic and structural properties was based on quantum chemical calculations performed by the density functional theory (DFT/M06-2X) method. The DFT calculations confirmed the existence of two forms in water solution: hydrazone form in acidic and neutral media and anionic form in basic media. The different contribution of azo and hydrazone canonical forms of anionic form is observed for dyes with electron-donating and dyes with electron-withdrawing groups. The dependence of absorption spectra and determined pKa values to the substituent type seems to be mostly due to azo/hydrazone canonical structure ratio in their anionic form.

BPC 157 therapy to detriment sphincters failure-esophagitis-pancreatitis in rat and acute pancreatitis patients low sphincters pressure.

Possibly, acute esophagitis and pancreatitis cause each other, and we focused on sphincteric failure as the common causative key able to induce either esophagitis and acute pancreatitis or both of them, and thereby investigate the presence of a common therapy nominator. This may be an anti-ulcer pentadecapeptide BPC 157 (tested for inflammatory bowel disease, wound treatment) affecting esophagitis, lower esophageal and pyloric sphincters failure and acute pancreatitis (10 µg/kg, 10 ng/kg intraperitoneally or in drinking water). The esophagitis-sphincter failure procedure (i.e., insertion of the tubes into the sphincters, lower esophageal and pyloric) and acute pancreatitis procedure (i.e., bile duct ligation) were combined in rats. Esophageal manometry was done in acute pancreatitis patients. In rats acute pancreatitis procedure produced also esophagitis and both sphincter failure, decreased pressure 24 h post-surgery. Furthermore, bile duct ligation alone immediately declines the pressure in both sphincters. Vice versa, the esophagitis-sphincter failure procedure alone produced acute pancreatitis. What's more, these lesions (esophagitis, sphincter failure, acute pancreatitis when combined) aggravate each other (tubes into sphincters and ligated bile duct). Counteraction occurred by BPC 157 therapies. In acute pancreatitis patients lower pressure at rest was in both esophageal sphincters in acute pancreatitis patients. We conclude that BPC 157 could cure esophagitis/sphincter/acute pancreatitis healing failure.