Effect of spin-orbit coupling on reduction potentials of octahedral ruthenium(II/III) and osmium(II/III) complexes

Reduction potentials of several M(2+/3+) (M = Ru, Os) octahedral complexes, namely, [M(H2O)6](2+/3+), [MCl6](4-/3-), [M(NH3)6](2+/3+), [M(en)3](2+/3+) [M(bipy)3](2+/3+), and [M(CN)6](4-/3-), were calculated using the CASSCF/CASPT2/CASSI and MRCI methods including spin-orbit coupling (SOC) by means of first-order quasi-degenerate perturbation theory. It was shown that the effect of SOC accounts for a systematic shift of approximately -70 mV in the reduction potentials of the studied ruthenium (II/III) complexes and an approximately -300 mV shift for the osmium(II/III) complexes. SOC splits the sixfold-degenerate (2)T(2g) ground electronic state (in ideal octahedral symmetry) of the M(3+) ions into the E((5/2)g) Kramers doublet and G((3/2)g) quartet, which were calculated to split by 1354-1573 cm(-1) in the Ru(3+) complexes and 4155-5061 cm(-1) in the Os(3+) complexes. It was demonstrated that this splitting represents the main contribution to the stabilization of the M(3+) ground state with respect to the closed-shell (1)A(1g) ground state in M(2+) systems. Moreover, it was shown that the accuracy of the calculated reduction potentials depends on the calculated solvation energies of both the oxidized and reduced forms. For smaller ligands, it involves explicit inclusion of the second solvation sphere into the calculations, whereas implicit solvation models yield results of sufficient accuracy for complexes with larger ligands. In such cases (e.g., [M(bipy)3](2+/3+) and its derivatives), very good agreement between the calculated (SOC-corrected) values of the reduction potentials and the available experimental values was obtained. These results led us to the conclusion that especially for Os(2+/3+) complexes, inclusion of SOC is necessary to avoid systematic errors of approximately 300 mV in the calculated reduction potentials.     

Facile dehalogenation of halogenated anilines and their derivatives using Al-Ni alloy in alkaline aqueous solution

This article describes the simple hydrodehalogenation of halogenated anilines and their derivatives by the action of Raney aluminium-nickel alloy in aqueous alkaline solution at room temperature. The reaction course was monitored by means of 1H nuclear magnetic resonance (NMR) spectroscopy and GC-MS spectra.      

Ecdysterone and its activity on some degenerative diseases

Beside ecdysone (1), ecdysterone (2) is one of the most common 5beta-cholest-7-en-6-one (ecdysteroid) derivatives, which, besides having a hormonal effect on invertebrates, possesses a number of favorable non-hormonal biological effects on mammals. The most interesting of these is that on degenerative diseases, one of which, up to now not clarified in detail, is the so-called adaptogenic effect (protection of the organism against adverse stress factors) associated with anabolic, gastroprotective, and antioxidant effects. A second group of favorable effects is the possibility of suppression of neurodegenerative processes and protection of the cardiovascular system (metabolic syndrome symptom suppression, antidiabetic activity, and protection of heart and blood vessels). Because of these properties, ecdysterone has the potential to be developed as a medicinal agent.     

Isolation and cholinesterase activity of Amaryllidaceae alkaloids from Nerine bowdenii

Amaryllidaceae species are known as ornamental plants. Some contain galanthamine, an acetylcholinesterase inhibitor. The chemical composition of the alkaloid extract of bulbs of Nerine bowdenii Watson has been analyzed by means of GC/MS. Twenty-two compounds were detected and nineteen of them identified, one of which was belladine. The alkaloid extract showed promising cholinesterase inhibitory activities against human blood acetylcholinesterase (HuAChE; IC50 = 87.9 +/- 3.5 microg/mL) and human plasma butyrylcholinesterase (HuBuChE; IC50 = 14.8 +/- 1.1 microg/mL). Belladine inhibited HuAChE and HuBuChE in a dose-dependent manner with IC50 values of 781 +/- 12.5 microM and 284.8 +/-4.2 microM, respectively.     

Partial Molar Volumes and Partial Molar Isentropic Compressions of <Emphasis Type="Italic">γ</Emphasis>-Butyrolactone and <Emphasis Type="Italic">ε</Emphasis>-Caprolactone at Infinite Dilution in Water at Temperatures (278.15 to 318.15) K and at Atmospheric Pressure

Density and speed-of-sound values at T = (278.15, 283.15, 288.15, 293.15, 298.15, 308.15, and 318.15) K and at atmospheric pressure were measured, for dilute aqueous solutions of γ-butyrolactone and ε-caprolactone, using an Anton Paar DSA 5000 vibrating-tube densimeter and sound analyzer. A small but significant effect of hydrolysis was observed for aqueous ε-caprolactone and a procedure for eliminating its effect was proposed and employed. Values of the partial molar volume and isentropic compression at infinite dilution were obtained from this experimental data by suitable extrapolation procedures and compared with available data from the literature. The group contribution of the methylene group was evaluated and compared with that obtained for other classes of aqueous cyclic solutes.     

Glass melting and its innovation potentials: The combination of transversal and longitudinal circulations and its influence on space utilisation

This work deals with the increase of the space utilisation caused by changes in glass circulations resulting from different temperature gradients in the melting channel. The space utilisation values were calculated by mathematical modelling of particle dissolution and bubble rising in a model melting channel. It has been found that for a given sand-dissolution time and bubble-growth rate, the space utilisation value was determined as the ratio between transversal and longitudinal temperature gradients. The highest space utilisation values for both dissolution and bubble removal are reached when both types of temperature gradients are combined and the transversal temperature gradient is 5–10 times higher than the longitudinal one. A cautious application of optimal conditions in the model glass furnace leads to an increase in the furnace space utilisation.     

The optimal parameters of bubble centrifuging in glass melts

The mathematical model of a multicomponent bubble in a glass melt under the influence of gravitational and centrifugal fields has been applied in the model TV glass. The optimal fining conditions have been examined in a rotating cylinder with the aim of determining their general features. All of the dependences between the bubble-removal time and the rotational velocity showed the region of bubble removal by centrifuging at low cylinder rotational velocities and the region of complete bubble dissolution when the rotation was intensive. The low rotational velocities, characterised by the minimal bubble-centrifuging time, appeared to be suitable for industrial application. Consequently, the influence of temperature, pressure and glass-layer thickness on the value of the optimal rotational velocity and optimal fining time of small-critical bubbles has been investigated in detail in a glass melt containing fining agent. The significant role of temperature and minor role of pressure have been proved and the identical features of bubble removal have been identified in cylinders with different radii and filling by glass but with the same average thickness of the glass layer on the cylinder walls.     

An experimental and theoretical study of stereoselectivity of furan-maleic anhydride and furan-maleimide diels-alder reactions

The stereoselectivity of the reaction of furan (1) with maleic anhydride (2) and maleimide (3) was studied experimentally and theoretically. Although the two reactions are highly similar with regard to their preference for endo and exo steroisomers, notable differences were experimentally observed and explained on the basis of calculated reaction-free energies and transition-state barriers. The experimental values of rate constants (k(1+2endo) = (1.75 +/- 0.48) x 10(-5); mol(-1) l s(-1); k(1+2exo) = (3.10 +/- 0.55) x 10(-5); mol(-1) l s(-1); k(1+3endo) = (1.93 +/- 0.082) x 10(-5); mol(-1) l s(-1), k(1+3exo) = (1.38 +/- 0.055) x 10(-5); mol(-1) l s(-1) all at 300 K) and the observed reaction course clearly confirm that neither of these reactions are prototypical examples of Diels-Alder [4 + 2] cycloadditions, whose dominant preference is for endo isomers. However, only by comparing their energetics-calculated at the CCSD(T) level of theory-with the analogous reactions involving cyclopentadiene (8) as a diene can these observations be understood. The low thermodynamic stability of furan [4 + 2] adducts opens retro-Diels-Alder reaction channels and overrules the very small kinetic preference (calculated and measured here) of initial formation for endo stereoisomers. On a macroscopic scale "an irregular"-thermodynamically more stable-exo stereoisomer was consequently observed as a dominant species.