Wyniki wyszukiwania - BazTech

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Zastosowanie topologicznej analizy gęstości elektronowej do opisu oddziaływań niekowalencyjnych

Bankiewicz B., Rybarczyk-Pirek A., Małecka M., Domagała M., Palusiak M.

Wiadomości Chemiczne

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2014

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[Z] 68, 5-6

457--486

EN

All atomic and molecular properties are governed by an electron density distribution. Thus, the methods that deal with an analysis of the electron density distribution should have a particular appeal for chemists and help to understand the electron structure of molecules. The Quantum Theory of Atoms in Molecules gives the unique opportunity to have an insight into a region (e.g., an atom) of a given system (e.g. a molecule), delivering partitioning scheme which is defined explicitly within the rigorous quantum theory, from one side, and is applicable for experimentally available set of observables, from the other side. In that way QTAIM delivers a chemist a theoretical tool to study a small part of a molecule only, instead of dealing with the total energy of a whole system. In consequence, QTAIM has become one of the most powerful utilities of modern chemistry, forming a bridge between advanced theoretical and experimental techniques. In particular the properties of the electron density function in the so-called bond critical point (BCP, the (3, -1) saddle point on electron density curvature) seem to be valuable information for chemists, since it was proven in many papers that the chemical bonding can be characterized and classified on the basis of electron density characteristics measured in BCPs . In this review we firstly give a brief introduction to the theory, explaining most basic terms and dependences. In the main part of the review we discuss application of QTAIM in the qualitative and quantitative analysis of several various noncovalent interactions, focusing readers attention on such aspects as classification of interactions and interaction energy assessment. Both theoretical and experimental approaches are taken into account. We also discuss extensions of QTAIM to the analysis of the so called source function – the method which additionally enlarge interpretative possibilities of its parent theory. Finally, we give some examples which perhaps escape a rigorous QTAIM definition of chemical bonding. We acquaint the potential reader with arguments being pro- and against the QTAIM-based deterministic model of a chemical bond.

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Relacja pomiędzy wiązaniem wodorowym wspomaganym rezonansem a aromatycznością

Palusiak M.

Wiadomości Chemiczne

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2010

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[Z] 64, 3-4

263-283

EN

Among the so called non-covalent interactions the hydrogen bond (H-bond) is probably the most frequently and the most thoroughly investigated. This is due to the fact that H-bond plays an essential role in many physical, chemical and biochemical processes. The strongest H-bonds are those assisted with additional effects, as for instance the resonance assisted H-bonds (RAHBs). The concept of RAHB was first proposed by Gilli and co-workers in 1989, and with the time it has become one of the most thoroughly investigated aspects from the field of structural chemistry. Originally, the definition of RAHB was directly connected with the resonance effect acting in RAHB motif (either intra- or intermolecular). Many scientists were exploring the phenomena of the RAHB. Thus, some controversies appeared in connection with the extra stabilization of the RAHB if comparing with its "non-resonance-assisted" counterparts. Some authors criticized the original explanation introduced by Gilli et al. and proposed alternative mechanism responsible for the relatively stronger H-bonding in the RAHB motifs. Since the resonance effect accompanying the formation of H-bridge in RAHBs is in fact a π-electron effect, it may interact with other π -electron effects acting in specific molecules, e.g. with substituent effect or aromatic đ -electron delocalization. In this way the mutual interaction between different đ -electron effects may occur, which may influence many physical and chemical properties of molecular systems under consideration, as for instance the strength of RAHB, local aromaticity, proton transfer barrier and many others. In this paper a short review on the current state of knowledge on RAHB will be presented. The special attention will be paid onto the interrelation between RAHB and local aromaticity in derivatives of polycyclic aromatic hydrocarbons.

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pi-Electron Communication Through the Metal Valence Shell –W, Mo and Fe Complexes Containing Maleimidato Moiety

Palusiak M.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 5-6

903-909

EN

The characterization of carbonyl–metal and maleimidato–metal bonding has been performed using the topological analysis of electron distribution function estimated for molecules of ( 5-C5H5)M(CO)3( 1-N-maleimidato) (M = W, Mo) and ( 5-C5H5)Fe(CO)2( 1-N-maleimidato). The Atoms in Molecules (AIM) approach has been applied for characterization of and -components of the metal–ligand bonds. The -electron communication between trans-placed ligands is present in Wand Mo derivatives. The ellipticity parameter is suggested to be a useful and highly sensitive parameter in the analysis of the metal–ligand bonding

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A New Chiral 4-[(E)-2-Ferrocenylvinyl]-1-methylpyridinium Iodide Exhibiting Bulk Second-Order Nonlinear Optical Properties

Janowska I., Zakrzewski J., Palusiak M., Nakatani K.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 5-6

1063-1070

EN

Two new chiral 4-[(E)-2-ferrocenylvinyl]-1-methylpyridinium iodides, having in the 2-position of the ferrocenyl group (R)-1-N,N-dimethylaminoethyl and (S)-2-methoxymethylpyrrolidin- 1-yl substituents were synthesized. The latter compound showed weak second harmonic generation efficiency (0.5 x urea) at 1907 m. The molecular structure and crystal packing of this compound were determined by single-crystal X-ray diffraction and are discussed in relation to its nonlinear optical properties.