Search results for "Coupling"
showing 10 items of 1862 documents
EXTENDED HÜCKEL MOLECULAR ORBITAL CALCULATION OF THE TEMPERATURE DEPENDENCE OF THE QUADRUPOLE SPLITTING OF [Fe(H2O)6] SiF6 AND KFeCl3
1976
A number of papers have appeared in which the temperature dependence of the quadrupole splitting has been treated, whereby covalency effects have been considered by introducing the orbital reduction factor k, with k ranging from 1.-0.7. There are, however, two problems : (1) k is unisotropic if the symmetry is lower than cubic, (2) the spin orbit coupling of the ligand electrons are usually neglected. These two problems have been treated here by using SCCEHMO [1] calculations on two examples, [Fe(H2O)6]SiF6 and KFeCl3, which have been previously delt with by other authors using ligand field theory [2, 3]. For both compounds the differences between the measured and the calculated quadrupole …
ChemInform Abstract: Excited State Decay of Cyclometalated Polypyridine Ruthenium Complexes: Insight from Theory and Experiment
2016
Deactivation pathways of the triplet metal-to-ligand charge transfer (3MLCT) excited state of cyclometalated polypyridine ruthenium complexes with [RuN5C]+ coordination are discussed on the basis of the available experimental data and a series of density functional theory calculations. Three different complex classes are considered, namely with [Ru(N^N)2(N^C)]+, [Ru(N^N^N)(N^C^N)]+ and [Ru(N^N^N)(N^N^C)]+ coordination modes. Excited state deactivation in these complex types proceeds via five distinct decay channels. Vibronic coupling of the 3MLCT state to high-energy oscillators of the singlet ground state (1GS) allows tunneling to the ground state followed by vibrational relaxation (path A…
Low-temperature optical absorption of nickel fluosilicate crystals
1964
Abstract The vibronic absorption spectrum of the Ni++ ion in an electric field of trigonal (nearly cubic) symmetry at temperatures down to 4°K is reported and analysed in terms of ligand field and vibronic theory. The positions, widths, shapes and strengths of the bands are satisfactorily explained, together with their associated fine structures. In particular, the complex structure of the red band is well explained in detail as a consequence of the mutual perturbation of the 1E and 3T4 levels, which strongly modifies the vibronic coupling and results in two fairly narrow bands, each showing resolved vibrational structure, superposed on a broad band. A Trees correction term, αL(L+1), helps …
Anion encapsulation promoted by anion⋯π interactions in rationally designed hexanuclear antiferromagnetic wheels: synthesis, structure and magnetic p…
2009
The reaction of Kpymca (pymca = pyrimidine-2-carboxylato anion) with MX2·6H2O and tmda (N,N,N′,N′-tetramethylethylenediamine) in 1 : 3 : 3 molar ratio, using a MeOH/water mixture (3 : 1) as solvent, afforded the hexanuclear complexes [M6(µ-pymca)6(tmda)6]X6·4H2O (M = NiII, X = ClO4−1, BF4−2; M = CoII, X = ClO4−3). The reaction of pymca with either Cu(ClO4)2·6H2O or Cu(BF4)2·6H2O did not lead to any definite product. However, in the presence of strong coordinating chloride anions the linear tetranuclear complex [Cu4(µ-pymca)3Cl(H2O)](ClO4)4·4.5H2O 4 could be obtained. The structures of 1–3 are very similar and consist of wheel-shaped hexanuclear [M6(µ-pymca)6(tmda)6]6+ cations, with pseudo-D…
Etherification of Functionalized Phenols with Chloroheteroarenes at Low Palladium Loading: Theoretical Assessment of the Role of Triphosphane Ligands…
2011
The present study highlights the potential of robust tridentate ferrocenylphosphanes with controlled conformation as catalytic auxiliaries in CO bond formation reactions. Air-stable palladium triphosphane systems are efficient for selective heteroaryl ether synthesis by using as little as 0.2 mol% of catalyst. These findings represent an economically attractive and clean etherification of functionalized phenols, electron-rich, electron-poor and para-, meta- or ortho-substituted substrates, with heteroaryl chlorides, including pyridines, hydroxylated pyridine, pyrimidines and thiazole. The etherification tolerates very important functions in various positions, such as cyano, methoxy, amino, …
Multi-scale dynamics simulations of molecular polaritons: The effect of multiple cavity modes on polariton relaxation
2021
It is included two versions of this item: the Accepted Version which is already Open Access and the Published Version which is under an embargo period till 2022-03-09.
Light and Primary Production Shape Bacterial Activity and Community Composition of Aerobic Anoxygenic Phototrophic Bacteria in a Microcosm Experiment
2020
ABSTRACT Phytoplankton is a key component of aquatic microbial communities, and metabolic coupling between phytoplankton and bacteria determines the fate of dissolved organic carbon (DOC). Yet, the impact of primary production on bacterial activity and community composition remains largely unknown, as, for example, in the case of aerobic anoxygenic phototrophic (AAP) bacteria that utilize both phytoplankton-derived DOC and light as energy sources. Here, we studied how reduction of primary production in a natural freshwater community affects the bacterial community composition and its activity, focusing primarily on AAP bacteria. The bacterial respiration rate was the lowest when photosynthe…
Gli Anapesti di Plauto e di Seneca
2014
Greek Marschanapaste were first divided into dimeters by Alexandrian philologists. This division (that reflects a syntactical tendency) influenced Roman dramatists deeply. Plautus composed real anapaestic dimeters sometimes ordering them as a κατὰ στίχον series, sometimes (and more frequently) coupling them as septenarii or octonarii, but he did not compose κατὰ σύστηµα series (as scholars generally suppose) and most of these series are more conveniently interpreted as octonarii mixed with septenarii. Seneca’s anapaests should still be interpreted as dimeters mixed with monometers (the dimeters are marked off by hiatus and indifferens, while sinaphia strangely enough operates only within a …
Iron‐Catalyzed Cross‐Couplings in the Synthesis of Pharmaceuticals: In Pursuit of Sustainability
2018
The scarcity of precious metals has led to the development of sustainable strategies for metal-catalyzed cross-coupling reactions. The establishment of new catalytic methods using iron is attractive owing to the low cost, abundance, ready availability, and very low toxicity of iron. In the last few years, sustainable methods for iron-catalyzed cross-couplings have entered the critical area of pharmaceutical research. Most notably, iron is one of the very few metals that have been successfully field-tested as highly effective base-metal catalysts in practical, kilogram-scale industrial cross-couplings. In this Minireview, we critically discuss the strategic benefits of using iron catalysts a…
Static Properties of a Simulated Supercooled Polymer Melt: Structure Factors, Monomer Distributions Relative to the Center of Mass, and Triple Correl…
2004
We analyze structural and conformational properties in a simulated bead-spring model of a non-entangled, supercooled polymer melt. We explore the statics of the model via various structure factors, involving not only the monomers, but also the center of mass (CM). We find that the conformation of the chains and the CM-CM structure factor, which is well described by a recently proposed approximation [Krakoviack et al., Europhys. Lett. 58, 53 (2002)], remain essentially unchanged on cooling toward the critical glass transition temperature of mode-coupling theory. Spatial correlations between monomers on different chains, however, depend on temperature, albeit smoothly. This implies that the g…