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    Wyświetlanie 1-6 z 6
    Tytuł:
    Betainy jako akceptory protonu
    Betaines as proton-acceptors
    Autorzy:
    Dega-Szafran, Z.
    Szafran, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172795.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    betainy
    kompleksy z wiązaniem wodorowym
    struktura
    betaines
    hydrogen bonded complexes
    molecular structure
    Opis:
    Ammonium alkanoates (ammonioalkanocarboxylates) are zwitterions (or inner salts, or betaines), because they possess formally charged ammonium and carboxylate groups separated by one or more sp3 carbon atoms. The chemistry of betaines has become a subject of particular interest due to their applications in biological research, especially with regard to their important role in aminoacid synthesis as methyl transfer agents. The crystals of many betaine complexes display interesting physical properties, exhibiting phase transitions with ferroelectric, antiferroelctric and ferroelastic behavior. Betaines containing a hydrophobic chain in the range of 8–20 carbon atoms show the unique properties characteristic for amphoteric surfactants and their current industrial application is in toiletries and personal care products. The conformational structure of zwitterionic molecules depends on several factors. The electrostatic attraction between two charged groups depends strongly on arm flexibility (energy differences between rotational trans and gauche isomers), bulkiness and hydration of charged groups preventing their close approach, solvent and arm electrical properties which control electrostatic attraction between two opposite charged groups, and polarization of solvent around the molecule caused by the dielectric discontinuity between solvent and solute interior (image charge effect). Electrostatic interaction is the common determinant and probably the most important element in structure-reactivity correlation in organic and biological systems. On the other hand, organic compounds are thought to be pure even though they may be a mixture of conformational isomers. This is because the isomers covert rapidly with each other at room temperature and their individual reactivates are little known. Occasionally the conformers may be stabilized in the crystallographic matrixes of polymorphic structures. This article describes structures of seven groups of aliphatic, aromatic and alicyclic betaines and numbers of their new hydrogen-bonded complexes with mineral and organic acids.
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 7-8; 609-628
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Charakterystyka oddziaływań międzycząsteczkowych : od dimerów do modeli mikrosolwatacyjnych
    Characterization of intermolecular interactions : from dimers to microsolvation models
    Autorzy:
    Panek, Jarosław J.
    Jezierska, Aneta
    Powiązania:
    https://bibliotekanauki.pl/articles/172152.pdf
    Data publikacji:
    2020
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    SAPT
    międzycząsteczkowe wiązania wodorowe
    mikrosolwatacja
    dimery
    trimery
    asocjaty molekularne
    intermolecular hydrogen bond
    microsolvation
    dimers
    trimers
    molecular associates
    Opis:
    Intermodular interactions play an important role in many processes at the molecular level. In the contemporary science, there is a growing interest concerning the characteristics of such interactions. Therefore, the computational chemistry can provide answers to many questions, which could not be answered using experimental methods. The Symmetry-Adapted Perturbation Theory (SAPT) method was applied to characterize the energy partitioning in dimers, trimers and microsolvation models. The investigated complexes belong to various classes of compounds, e.g. • dimers of: NH3 ˑˑˑHX, HF-pyridine, cycloalkanes, hypohalous acids; • trimers of: NH3 ˑˑˑNH3ˑˑˑHF or NH3ˑˑˑHFˑˑˑHF; • microsolvation models (biotin - water molecules). The current study summarizes recent years of our research devoted to the intermolecular interactions.
    Źródło:
    Wiadomości Chemiczne; 2020, 74, 9-10; 645-662
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Struktura a nieelastyczne rozpraszanie neutronów przez kryształy molekularne z wiązaniami wodorowymi
    Structure and inelastic neutron scattering by the molecular crystals with the hydrogen bonds
    Autorzy:
    Rok, M.
    Bator, G.
    Sobczyk, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/171492.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    kompleksy molekularne
    wiązanie wodorowe
    struktura krystaliczna
    rozpraszanie neutronów
    dynamika cząsteczek w fazie stałej
    molecular complexes
    hydrogen bonds
    crystal structure
    neutron scattering
    molecular dynamics in the solid state
    Opis:
    The molecular crystals, which are built of organic or organic-inorganic molecules, are characterized by the weak intermolecular interactions. From the viewpoint of the potential applications in electronics or optoelectronics the electric properties of the crystals are essential. In turn these properties are related to their crystal structure as well as the dynamics of the molecules in the solid state. The existence of the hydrogen bonds in the crystal structures, conventional and unconventional, is crucial from the viewpoint of the electric properties of the crystals. The dynamics of methyl groups present in the structure can be a measure of the molecular interactions in the crystals. In this work the dynamical properties, first of all taking into account the research results concerning the neutron scattering, will be discussed. The neutron technique is very effective as regards the methyl group dynamics investigations. The relationship between a formation of the conventional and unconventional hydrogen bonds and a tunneling of the methyl groups at low temperature will be discussed. The method of the interpretation of the INS spectra will be described taking into account the theoretical model, the parameters of which are fitted to the experimental data. The examples will regard the following molecular crystals: p-N,N’-1,10-tetraacethyldiaminodurene (TADD) (Figs. 2 and 4), 2,3,5,6-tetramethylpyrazine with chloranilic acid (TMP·CLA) (Figs. 5, 6 and 7), 2,3,5,6- tetramethylpyrazine with bromanilic acid (TMP·BRA) (Figs. 5 and 6) and the crystal of 3,4,7,8-tetramethylphenantroline (Me4phen) and its complex with picric acid (Me4phen·PIC) (Figs. 8 and 9). In this paper we have shown that the surrounding of the methyl group and its interactions with the adjacent molecules has a stronger effect than the changes in the electronic charge density in the molecule.
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 7-8; 533-557
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Właściwości czasowo-rozdzielcze słabych międzycząsteczkowych wiązań wodorowych C-H···F
    Time-resolved properties of intermolecular C-H···F hydrogen bonds
    Autorzy:
    Polańska, Marta
    Rodziewicz, Paweł
    Powiązania:
    https://bibliotekanauki.pl/articles/27310029.pdf
    Data publikacji:
    2023
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    wiązanie wodorowe
    teoria funkcjonału gęstości
    dynamika molekularna Cara i Parrinello
    hydrogen bond
    density functional theory
    Car-Parrinello molecular dynamics
    Opis:
    The hydrogen bond is one of the most important and interesting phenomena in nature. In this publication we will shed light on the discovery of hydrogen bond and a time evolution of its definition in the last 100 years. Both structural and spectroscopic parameters of the hydrogen bond will be discussed. A special focus will be given to the latest IUPAC definition of the hydrogen bond and its consequences to scientific research. The main aim of this study is to highlight theoretical studies based on first principles calculations and molecular dynamics simulations which not only support experimental results but also provide parameters which are crucial to understand the nature of hydrogen bonds. Particular attention will be given to methods and theoretical ideas used in the computational studies of hydrogen bonds. Utilizing static DFT/ab initio calculations and molecular dynamics simulations enables comparison of different binding energies and studying time evolution of the hydrogen-bonded molecular system on the atomistic level. We will discuss time-resolved properties of weak intermolecular hydrogen bonds, using as an example C-H···F containing model systems, namely F3CH*(HF)n molecular complexes and (F3CH)2-4 aggregates.
    Źródło:
    Wiadomości Chemiczne; 2023, 77, 9-10; 899--919
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Efekt kooperatywności oddziaływań iekowalencyjnych w wybranych układach molekularnych stabilizowanych wiązaniami wodorowymi i halogenowymi
    Cooperativity effect in noncovalent interactions of selected molecular complexes stabilised by hydrogen and halogen bonds
    Autorzy:
    Domagała, Małgorzata
    Dominikowska, Justyna
    Palusiak, Marcin
    Powiązania:
    https://bibliotekanauki.pl/articles/172440.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    wiązanie halogenowe
    wiązanie wodorowe
    energia oddziaływania
    efekt kooperatywny
    modelowanie molekularne
    halogen bond
    hydrogen bond
    interaction energy
    cooperativity effect
    molecular modelling
    Opis:
    Among various so-called weak interactions, a halogen bond [8 and references therein] is currently probably one of more explored by researchers. This is due to the fact that it has several properties in common with the hydrogen bonding, and thus, similarly as already well characterised H-bond, it may have a crucial role in different physical, chemical, and biological processes. This bond is formed due to stabilising interactions between a region of positive charge located on a surface of the halogen atom and the other atomic center possessing the electron charge surplus (e.g. a lone pair) [8]. The region of positive charge appears on the halogen atom surface due to deformation of its electron cloud resulting in its ellipsoidal shape with the short axis opposite the covalent bond and the long axis in the perpendicular direction [11]. This results in a particular distribution of local charges on the atomic surface, as shown in Figure 1. As a consequence the halogen atom may exhibit a dual character, acting as either electron charge donor or acceptor, depending on the type of interaction and the direction of the appearing interactomic contact. A good example of such situation is shown in Figure 2. Thus, one may consider the situation when two interactions are formed simultaneously and the halogen atom acts as an electron charge donor and acceptor at the same time. For such situation the synergism of both interactions may strengthen complexation. In order to analyze that case, various representative complexes were investigated [13, 17, 18, 20, 21] by means of many-body interaction approach [5, 6]. In general, it appears that as distinct to hydrogen bond [2–4], the synergism is rather weak, with some exceptions for iodine atom due to stronger halogen bonds formed by that atomic centre [13, 17, 18]. In the case of halo-amine tetramers [21] the additional stabilising effect derived from back bonding of π type was found – for the first time for a halogen bond.
    Źródło:
    Wiadomości Chemiczne; 2019, 73, 1-2; 33-52
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Molowa entropia orientacyjna i struktura cieczy zasocjowanych
    Molar orientation entropy and structure of the self-associated liquids
    Autorzy:
    Jadżyn, J.
    Świergiel, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/172403.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    dipole molekularne
    przenikalność statyczna
    entropia orientacyjna
    ciecz
    wiązania wodorowe
    przejście fazowe ciecz izotropowa-nematyk
    molecular dipoles
    static permittivity
    orientation entropy
    liquids
    hydrogen bonds
    isotropic liquids to nematic phase transition
    Opis:
    Research on the structural effects of intermolecular interactions not only brings us closer to a better understanding the macroscopic properties of liquids, but also allows one to modify these properties. Intermolecular dipolar couplings and hydrogen bonds are the most common interactions in liquids leading to formation of multimolecular entities with various structures. The natural rival of these interactions is the thermal agitation of molecules (kT), which aims to destroy the emerging structures. In this paper we present an experimental method to estimate the way of molecular self-assembly resulting from the simultaneous action of kT and intermolecular interactions. The method is based on the study of dipolar orientation effects induced by an applied electric field. As an experimental source of the information on these effects is temperature derivative of the static permittivity of tested liquid. That derivative is proportional to the liquid entropy change due to the ordering action of the electric field on the molecular dipoles. Here, we present the experimental results on temperature dependence of the static permittivity and increment of the orientation entropy of liquids where the self-association process realizes with two ways: dipolar couplings and hydrogen-bonds.
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 7-8; 517-532
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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