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Wyszukujesz frazę "Grabowski, S" wg kryterium: Autor


Wyświetlanie 1-2 z 2
Tytuł:
Wiązanie wodorowe i inne oddziaływania typu kwas Lewisa-zasada Lewisa
The hydrogen bond and the other Lewis acid-Lewis base interactions
Autorzy:
Grabowski, S. J.
Powiązania:
https://bibliotekanauki.pl/articles/171998.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
wiązanie wodorowe
wiązanie halogenowe
wiązanie wodorkowe
oddziaływanie kwas Lewisa-zasada Lewisa
teoria Atomy w Cząsteczkach
hydrogen bond
halogen bond
hydride bond
Lewis acid-Lewis base interaction
atoms in molecules theory
AIM
Opis:
Hydrogen bond is analyzed very often since its importance in numerous chemical, physical and biological processes is very well known. It covers the broad range of various interactions; sometimes this is the subject of discussions and polemics if some of them may be classified as hydrogen bonds. This is because there are numerous definitions of hydrogen bond interaction, often they are hardly accepted since they are not univocal. For example one can mention different types of the proton acceptors for hydrogen bonds; one center electronegative atoms, multi-center acceptors such as đ-electrons or even ó-electrons. There are the other interactions which play the key role in various processes and phenomena. All are often named as no-covalent interactions but the other term, Lewis acid–Lewis base interactions seems to be more accurate. One can mention halogen bond, hydride bond or dihydrogen bond. These interactions may be treated as counterparts or competitors of hydrogen bond. The common characteristic for them, including hydrogen bond, is the electron charge transfer from the Lewis base to the Lewis acid. It was found that the amount of this transfer corresponds roughly to the strength of the interaction. In recent years the ó-hole concept was introduced and developed and it was applied to the Lewis base–Lewis acid interactions. According to this concept the atomic centers are characterized by the presence of the regions of positive and negative electrostatic potentials; very often both regions are detected even for atoms which are commonly known as electronegative ones. In such a way halogen atoms, especially if connected by covalent bond with carbon, may act as Lewis acids and also as Lewis bases. In the first case the halogen bond is formed, recently extensively studied. In this review the characteristics of different Lewis base–Lewis acid interactions are given as well as their common features are presented.
Źródło:
Wiadomości Chemiczne; 2011, 65, 11-12; 975-1001
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Borowce jako centra kwasów Lewisa w oddziaływaniach międzycząsteczkowych : porównanie z wiązaniami wodorowymi
Triels as centers of Lewis acids in intermolecular interactions : comparison with hydrogen bonds
Autorzy:
Grabowski, S. J.
Powiązania:
https://bibliotekanauki.pl/articles/172397.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
wiązanie wodorowe
wiązanie borowcowe
potencjał elektrostatyczny
dziura σ
dziura π
przesunięcie ładunku elektronowego
struktury krystaliczne
hydrogen bond
triel bond
electrostatic potential
σ-hole
π-hole
electron charge shift
crystal structures
Opis:
The triel bonds are analyzed and compared with the hydrogen bond interaction. The triel bonds belong to the class of interactions that are named as the σ-hole and π-hole bonds. The σ-hole bond is an interaction between the σ-hole characterized by the positive electrostatic potential and the electron rich regions such as lone electron pairs, π-electron systems, in other words, centers paying a role of Lewis bases. The σ-holes may be observed for elements of the 14–18 groups of the periodic system and the corresponding interactions with Lewis bases are named; tetrel, pnicogen, chalcogen, halogen and aerogen bonds, respectively. On the other hand, π-holes also characterized by the positive electrostatic potential are observed for centers in planar molecules or planar fragments of molecules in regions above those planes. π-holes may be attributed to triel centers (13th group of the periodic system). The boron and aluminium trihydrides and trihalides are examples of molecules where triels are characterized by π-holes. The mechanism of the triel bond formation is very similar to the mechanism of the formation of the hydrogen bond. It is the Lewis acid – Lewis base interaction where the electron charge transfer from the base unit to the acid one is observed. Next there is outflow of the electron charge from the triel center to the other parts of the Lewis acid unit; in other words the positive charge of the triel center increases as a result of complexation. The triel bonds are often very strong and often they possess characteristics of typical covalent bonds; this is confirmed by the QTAIM (Quantum Theory of Atoms in Molecules) and NBO (Natural Bond Orbital) approaches. For example, for the triel bonds the bond paths between the triel center and the Lewis base center are observed with the bond critical points (BCPs) attributed to those paths. Similarly for the A-H…B hydrogen bonds the H…B bond paths are observed. The parameters of those BCPs often indicate the covalent character of the triel bonds and analogously those characteristics for H-bonds may also indicate the covalent character of the latter interactions. It is very interesting that the triel bonds are observed experimentally in the real systems; for example in crystal structures. The triel center which is trivalent and possesses the trigonal configuration is hypovalent; it means that the octet rule is not obeyed here because of the valence electrons´ deficiency (the triel center possesses six valence electrons in such species). Thus it may interact with one Lewis base ligand reaching rather stable octet and tetrahedral configuration. If the trivalent triel center interacts with two Lewis base ligands thus it may lead to the configuration of the trigonal bipyramid with the hypervalent and pentavalent triel center. These kinds of the triel species occur in crystal structures that are described here.
Źródło:
Wiadomości Chemiczne; 2017, 71, 7-8; 447-471
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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