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Wyświetlanie 1-19 z 19
Tytuł:
Ultrasonic Studies of Intermolecular Interactions in System Methanol-N,N-Diisobutylformamide
Autorzy:
Miecznik, P.
Powiązania:
https://bibliotekanauki.pl/articles/1963258.pdf
Data publikacji:
1997-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.35.+d
Opis:
The ultrasonic velocity and density of methanol solutions of N,N-diisobutylformamide (DBFA) were measured at -5, 5 and 15° C over the entire concentration range. The compressibility, excess compressibility, partial molar compressibility, excess molar volume, partial molar volume were calculated. The concentration dependencies of the velocity and density are nonlinear. On taking account of the results for excess molar volume and excess molar compressibility, the minima of these functions are ascribed to the complex formation type CH$\text{}_{3}$OH:DBFA and CH$\text{}_{3}$OH:2 x DBFA. These complexes are formed by hydrogen bond between methanol and N,N-diisobutylformamide molecules. The strong changes in the concentration dependencies of partial molar volume and partial molar compressibility (within range 0...0.1 mol. fraction amide) show that methanol and DBFA have strong interactions in the low-mole-fraction regions, too.
Źródło:
Acta Physica Polonica A; 1997, 91, 3; 543-553
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Intermolecular Interactions between TNAZ and H2O: a DFT Study
Autorzy:
Oftadeh, M.
Selahvarzi, S.
Keshavarz, M. H.
Powiązania:
https://bibliotekanauki.pl/articles/358486.pdf
Data publikacji:
2013
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
1,3,3-trinitroazetidine (TNAZ)/H2O complex
intermolecular interaction
DFT
natural bond orbital
thermodynamic properties
Opis:
All of the possible TNAZ/H2O complexes (1, 2 and 3), as well as the uncomplexed form, were fully optimized with the density functional method. Complex 3 was the most stable, with the largest corrected intermolecular interaction energy. Charge redistribution mainly occurs on the adjacent N–O...H atoms of the submolecules. Strong hydrogen bonds predominantly contribute to the interaction energies. It is energetically and thermodynamically unfavourable for TNAZ to bind with H2O and to form any stable complexes at room temperature.
Źródło:
Central European Journal of Energetic Materials; 2013, 10, 2; 289-300
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Intermolecular Interactions in Organic Dye Monolayers Formed by Langmuir-Blodgett Technique
Autorzy:
Bauman, D.
Powiązania:
https://bibliotekanauki.pl/articles/1538188.pdf
Data publikacji:
2010-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.18.-g
68.47.Pe
78.40.Me
78.55.Kz
Opis:
Langmuir and Langmuir-Blodgett films of some organic dyes (perylene-like dyes, derivatives of 4-amino-naphthali-mide, derivatives of naphthoylene-benzi-mida-zole, azo dyes) and their mixtures with thermotropic liquid crystal or arachidic acid have been investigated. Surface pressure as a function of the mean molecular area for the Langmuir films were measured and information about organization of molecules at the air-water interface has been obtained. Absorption spectra in situ for the Langmuir films and both absorption and fluorescence spectra for Langmuir-Blodgett films were recorded. The results obtained from spectroscopic studies have led to conclusions about formation of self-aggregates of dye molecules, both in ground and excited states, at the phases interfaces.
Źródło:
Acta Physica Polonica A; 2010, 117, 4; 525-531
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-ray Analysis of Intermolecular Interactions in Liquid 2-chloronaphthalene at 353 K
Autorzy:
Drozdowski, H.
Powiązania:
https://bibliotekanauki.pl/articles/2036984.pdf
Data publikacji:
2003-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.25.Em
Opis:
The aim of the study was to examine the structure of liquid 2-chloronaphthalene C$\text{}_{10}$H$\text{}_{7}$-Cl at 353 K by the X-ray diffraction method. Monochromatic radiation Mo K$\text{}_{α}$,λ= 0.71069Å was used to determine the scattered radiation intensity between S$\text{}_{min}$=4πsinθ$\text{}_{min}$/λ=0.430Å$\text{}^{-1}$ and S$\text{}_{max}$= 4π sinθ$\text{}_{max}$/λ=14.311Å$\text{}^{-1}$. The curves of reduced intensity were analysed by the reduction method of Blum and Narten. Experimental distribution of X-ray scattered intensity was compared with theoretical results predicted for a proposed model of 2-chloronaphthalene molecule. The differential radial distribution function 4π r$\text{}^{2}$Σ$\text{}_{j,k}^{n}$ K$\text{}_{j}$[ρ$\text{}_{k}$(r)-ρ$\text{}_{0}$] was calculated and some intra- and intermolecular distances in liquid 2-chloronaphthalene were determined. X-ray structural analysis was applied to determine the packing coefficient of 2-chloronaphthalene molecules at 353 K. The intermolecular distance Cl ··· Cl' was also determined as 7.90±0.15Å. A simple model of short-range arrangement of the molecules was proposed, which seems to be valid for other weakly polar monosubstituted naphthalene derivatives in the liquid phase.
Źródło:
Acta Physica Polonica A; 2003, 104, 5; 441-458
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Role of Intermolecular Interactions in the Electro-Optical Kerr Effect in Liquid Alkanes
Autorzy:
Prezhdo, O. V.
Switek, L.
Zubkova, V. V.
Prezhdo, V. V.
Powiązania:
https://bibliotekanauki.pl/articles/2043659.pdf
Data publikacji:
2005-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
31.70.Dk
78.20.Fm
Opis:
The electro-optical Kerr effect of n-alkanes from C$\text{}_{5}$ to C$\text{}_{16}$ was investigated in gas phase, liquid phase, and solution. The values of the Kerr constants in gas phase are noticeably distinguishable from those in liquids, where the molecules interact by the London dispersion forces. Both the energy of the dispersion interaction and the difference in the Kerr constants in liquid and gas phase grow with molecular size, indicating the key influence of the interaction on the magnitude of the Kerr effect. Several orientation and molecular-statistical theories of electro-optical Kerr effect were applied to model the change in electro-optical Kerr effect due to the dispersion force. Most theories show significant divergence compared to the experimental data. It is argued that the decisive contribution to electro-optical Kerr effect in liquids and the deviations between the experiment and theory arise due to local liquid structures that collectively orient in the external electric field.
Źródło:
Acta Physica Polonica A; 2005, 108, 3; 429-447
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
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:
Magnetic interactions in frozen solutions of ironporphyrins
Autorzy:
Dziedzic-Kocurek, K.
Okła, D.
Stanek, J.
Powiązania:
https://bibliotekanauki.pl/articles/147882.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
Fe-porphyrins
intermolecular interactions
magnetic relaxation
Mössbauer spectroscopy
Opis:
The powder samples of meso-tetraphenyloporphyrin iron(III) chloride and ferriprotoporphyrin IX chloride and their frozen in solutions N,N-dimethylformamide were studied by Mössbauer spectroscopy. The variation of the outer ligands of the porphyrin rings modifies their magnetic properties but the major influence on the magnetic relaxation process exerts the intermolecular magnetic interactions, which are eliminated in dilute solutions.
Źródło:
Nukleonika; 2013, 58, 1; 83-86
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ammonium nitrate phase state stabilization with small amounts of some organic compounds
Autorzy:
Golovina, N.
Nechiporenko, G.
Nemtsev, G.
Zyuzin, I.
Manelis, G. B.
Lempert, D.
Powiązania:
https://bibliotekanauki.pl/articles/358906.pdf
Data publikacji:
2009
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
ammonium nitrate
phase transitions
phase stabilization
intermolecular interactions
Opis:
The investigation considers phase stabilization of ammonium nitrate for considerable extension of its application area including new generation of gas-generating compositions for airbag inflators. It was shown that alloys of ammonium nitrate with small amounts (2-10%) of some organic compounds can have no phase transitions or at least have only one instead of three ones in initial ammonium nitrate. The mostly effective as stabilizers are the compounds that have rather close crystallographic parameters. A strong donor-acceptor interaction between nitrate-anion and organic molecules are found. Using quantum-chemical calculations, X-ray analysis, X-ray phase analysis, UV- and IR-spectroscopy it was found a new ammonium nitrate phase state in its alloy with some organic additives. This state is stable in temperature range between -50 and +100 C.
Źródło:
Central European Journal of Energetic Materials; 2009, 6, 1; 45-56
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-ray diffraction and vibrational spectroscopic studies of the intermolecular interactions on the grinding and compaction behaviours of lopinavir and ritonavir crystals
Autorzy:
Ainurofiq, Ahmad
Setianto, Arif B.
Nugraha, Yuda P.
Suendo, Veinardi
Uekusa, Hidehiro
Soewandhi, Sundani N.
Powiązania:
https://bibliotekanauki.pl/articles/895537.pdf
Data publikacji:
2020-04-29
Wydawca:
Polskie Towarzystwo Farmaceutyczne
Tematy:
compression
grinding
Vibrational spectroscopy
Ritonavir
intermolecular interactions lopinavir
crystal behaviour
Opis:
Lopinavir (LPV) and ritonavir (RTV) are anti-viral drugs used in combination and commonly prepared through hot-melt extrusion techniques. Mechanical processes are greatly involved, including blending and milling. Therefore, the crystal behaviour of LPV and RTV under the mechanical process is an interesting study. Here, the LPV, RTV, and their mixtures were processed by two different treatments: grinding and compression processes. The solid-state properties of the drugs were evaluated by powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM). Single-crystal XRD analysis was also carried out to confirm the packing structure in the crystal lattice. It was observed that LPV was very sensitive to the grinding process, where it tends to form an amorphous solid in both the pure and mixture forms. On the other hand, RTV has a very stable crystalline structure and was able to retain its crystallinity even under grinding. Both LPV and RTV were observed to be quite stable under compression, where both retained their crystalline form with only slight changes in their d-spacing values. This study highlighted the molecular origin of LPV and RTV crystal behaviour after grinding and compression processes.
Źródło:
Acta Poloniae Pharmaceutica - Drug Research; 2020, 77, 2; 259-269
0001-6837
2353-5288
Pojawia się w:
Acta Poloniae Pharmaceutica - Drug Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calculations of intermolecular interactions of D-fructose with the HyperChem avaible programs
Obliczanie oddzialywan miedzyczasteczkowych D-fruktozy za pomoca programu HyperChem
Autorzy:
Mazurkiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/1373083.pdf
Data publikacji:
1997
Wydawca:
Instytut Rozrodu Zwierząt i Badań Żywności Polskiej Akademii Nauk w Olsztynie
Tematy:
D-fruktoza
program HyperChem
sacharydy
oddzialywania miedzyczasteczkowe
Opis:
The energetically preferred isomer-conformers of D-fructose under vacuum and in aqueous solutions were determined involving the AMI and MM+ calculations, both available in the HyperChem program. Both methods were fairly compatible when the calculations of interactions under vacuum were considered. In aqueous solution, the calculations according to both methods were apparently not consistent with one another. However, the energetical differences which decide on the priority of certain isomer-conformers were almost negligible.
Stosując metody AMI і MM+ wyznaczono energetycznie uprzywilejowane struktury izomerów-konformerów D-fruktozy w próżni i w roztworze wodnym. Obie metody obliczeniowe są dostępne w programie HyperChem i stosuje się je do obliczeń strukturalnych oraz oddziaływań międzycząsteczkowych. Obie metody, chociaż zasadniczo różniące się w założeniach przy określaniu dominujących izomerów-konformerów w próżni dały bardzo jakościowo podobne wyniki (tab. 1 i 2). W roztworach wodnych wyniki uzyskane obydwoma metodami tylko pozornie są różne (tab. З i 4). Ciepła tworzenia izomerów-konformerów uprzywilejowanych przez obie metody obliczeniowe są praktycznie identyczne. Metoda MM+ wydaje się zawodzić w przypadku gdy pożądane są bardziej szczegółowe informacje, na przykład określenie składu i struktury hydratów D-fruktozy i prawdopodobnie innych sacharydów, oraz określenie hydrofilowej i hydrofobowej strony sacharydu.
Źródło:
Polish Journal of Food and Nutrition Sciences; 1997, 06, 2; 31-40
1230-0322
2083-6007
Pojawia się w:
Polish Journal of Food and Nutrition Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Proces samo-dysproporcjowania enancjomerów podczas chromatografii kolumnowej
Self-disproportionation of enantiomers via column chromatography
Autorzy:
Wzorek, Alicja
Kwiatkowska, Magdalena
Urbaniak, Mariusz
Gawdzik, Barbara
Powiązania:
https://bibliotekanauki.pl/articles/27310046.pdf
Data publikacji:
2023
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
chiralność
chromatografia
asocjacja
enancjomeryczne wzbogacanie
oddziaływania międzycząsteczkowe
chirality
chromatography
association
enantiomeric enrichment
intermolecular interactions
Opis:
The review is devoted to self-disproportionation of enantiomers (SDE) phenomenon which has been observed for many different classes of chiral organic compounds. The SDE phenomenon occurs when the fractionation of an enantioenriched sample due the application of a physicochemical process under achiral conditions results in the variation of the proportion of the enantiomers present across the fractions, though the overall composition in terms of the sample ee remains unchanged. The SDE process can be considered in terms of separating the excess enantiomer from the racemate. The basic terminology related to SDE was described. The formation of the SDE under chromatographic conditions is the result of an association process occurring in a solution of a chiral, non-racemic compound. Information on preferred interactions leading to homo-/heterochiral supramolecules can be provided by quantum chemical calculations, NMR spectroscopy and comparison of crystal structures of the racemic and enantiomeric crystals. Several examples of the chromatographic experiments with different classes of compounds were given in two purposes 1) to highlight the possibility of application SDE during column chromatography as the method for enantiopurification of the chiral, non-racemic compounds; 2) to demonstrate that a standard workup (chromatographic purification, evaporation) can alter the stereochemical outcome of asymmetric reactions.
Źródło:
Wiadomości Chemiczne; 2023, 77, 5-6; 425--448
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
Tytuł:
Wpływ anestetyków wziewnych na modelową błonę biologiczną
Influence of inhalation anesthetics on a model biological membrane
Autorzy:
Horochowska, Martyna
Cieślik-Boczula, Katarzyna
Rospenk, Maria
Powiązania:
https://bibliotekanauki.pl/articles/171702.pdf
Data publikacji:
2019
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
anestetyki wziewne
anestezja
słabe oddziaływania międzycząsteczkowe
błona lipidowa
inhalation anesthetics
anesthesia
weak intermolecular interactions
lipid membrane
Opis:
General anesthesia is defined as impairment of the central nervous system (UON) caused by intravenous or volatile anesthetics. The state of loss of consciousness or even amnesia and the disappearance of perception into external stimuli is achieved by the use of a large group of chemical compounds. The use of nitrous oxide in 1844 revolutionized surgery and medicine at that time. From that moment, anesthesiology develops dynamically, allowing more and more complex procedures. Despite more than 170 years of history of anesthesia, understanding the mechanism of reversible loss of awareness and sensitivity to pain caused by the action of general anesthetics is one of the greatest challenges of modern pharmacology and neuroscience. Incredibly high diversity of anesthetics, including both noble gases and complex steroids, combined with human sensation makes the above problem extremely difficult to solve. The reversibility of the anesthesia phenomenon suggests that the analyzed phenomenon is based on disturbance of weak intermolecular interactions, such as hydrogen bond or van der Walls forces. Anesthetic molecules may bind directly to the hydrophobic region of protein, which causes its conformational changes or disturb ion channel activity by anesthetic-induced perturbations of lipid bilayers. The mechanism of anesthesia is thus very often attributed to both protein and lipid membrane targets. The influence of anesthetic molecules on biomolecular systems can be studied successfully using many different physico-chemical methods, such as, infrared, fluorescence or nuclear magnetic resonance spectroscopy. Vibrational circular dichroism as well as differential scanning calorimetry can also be used.
Źródło:
Wiadomości Chemiczne; 2019, 73, 3-4; 263-285
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badania rozkładu gęstości elektronowej w kryształach, czyli jak zobaczyć szczegóły struktury elektronowej cząsteczek
Electron density distribution in crystals or how to see the details of the electronic structure of molecules
Autorzy:
Kubicki, M.
Powiązania:
https://bibliotekanauki.pl/articles/171566.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
rozkład gęstości elektronowej
model multipolowy
oddziaływania międzycząsteczkowe
pochodne 4-nitroimidazolu
electron density distribution
multipolar model
intermolecular interactions
4-nitroimidazole derivatives
Opis:
X-ray structural analysis might be regarded as a method of visualizing molecules as they appear in the crystals. The model, which is conventionally and universally used in this method, the Independent Atom Model (IAM) assumes that the electron density distribution, which scatters the X-rays is built of the spherically-symmetrical, neutral atoms. This model is responsible for the unprecedented success of X-ray structural analysis, which reflects in about one million crystal structures (i.e. the sets coordinates of the atoms constituting the molecules) deposited in the various databanks (cf. Fig. 1), and in the speed and accuracy which the method has reached. In principle, in few hours one can get the complete information about the crystal structure. But this success is accompanied by negligence of the scientific virtue hidden beyond the IAM. In fact, it was known from the very beginning of the X-ray diffraction studies by von Laue and Braggs, that some fine details of the electron density distribution should be available. The technological advance (four-circle diffractometers, powerful X-ray sources, fast computers etc.) caused that in 1960’s the time was ripe for the development of the experimental studies of details of electron density distribution in the crystals, beyond the IAM. The early experiments by Coppens and co-workers proved that this information – about the electron density transferred to the covalent bonds, lone pairs, even intermolecular interactions – can actually be obtained and analyzed (Fig. 2). The need for the model which could be used in the least-squares procedure led to the formulation of so-called pseudoatom models, including the most popular till now, Hansen-Coppens model (eq. 2) in which the aspherical part is described in terms of real spherical harmonics. In this paper, the basics of the electron density studies is described in some detail, including the step-by-step description of a typical procedure from the experiment to the final steps of refinement. An example of the analysis of the high-resolution structure of 1,2-dimethyl-4-nitro-5-morpholine-imidazole hydrate is used to show an application of this method in studying the intermolecular interactions, including weak C-H···O and C-H···N hydrogen bonds. It is shown that the multipolar model is able to deliver more informations than the promolecular model with spherically symmetrical electron distributions.
Źródło:
Wiadomości Chemiczne; 2014, 68, 5-6; 403-427
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies on intermolecular interactions in monoethanolamine-water liquid mixtures by means of H-NMR spectra and electric permittivities
Badania oddziaływań międzymolekularnych w mieszaninach monoetanoloaminy z wodą metodą pomiaru ich widm H-NMR i przenikalności elektrycznej
Autorzy:
Kinart, Cezary M
Powiązania:
https://bibliotekanauki.pl/articles/944824.pdf
Data publikacji:
1993
Wydawca:
Uniwersytet Łódzki. Wydawnictwo Uniwersytetu Łódzkiego
Źródło:
Acta Universitatis Lodziensis. Folia Chimica; 1993, 10
0208-6182
Pojawia się w:
Acta Universitatis Lodziensis. Folia Chimica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Studies on intermolecular interactions in pyridine-water liquid mixtures by means of ¹H-NMR spectra and electric permittivity values
Badania oddziaływań międzymolekularnych w mieszaninach Pirydyny z wodą metodą pomiaru ich widm ¹H-NMR i przenikalności elektrycznej
Autorzy:
Kinart, Cezary M
Powiązania:
https://bibliotekanauki.pl/articles/944822.pdf
Data publikacji:
1993
Wydawca:
Uniwersytet Łódzki. Wydawnictwo Uniwersytetu Łódzkiego
Źródło:
Acta Universitatis Lodziensis. Folia Chimica; 1993, 10
0208-6182
Pojawia się w:
Acta Universitatis Lodziensis. Folia Chimica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elektrooptyczny efekt Kerra w chemii
Electrooptic Kerr effect in chemistry
Autorzy:
Prezhdo, O.
Olan, K.
Zubkowa, W.
Preżdo, W.
Powiązania:
https://bibliotekanauki.pl/articles/171825.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
elektrooptyczny efekt Kerra
analiza konformacyjna
wewnątrzcząsteczkowe oddziaływania
oddziaływania wewnątrzcząsteczkowe
oddziaływania międzycząsteczkowe
polaryzowalność
moment dipolowy
stała Kerra
electro-optical Kerr effect
conformational analysis
intra-molecular interactions
intermolecular interactions
polarizability
dipole moment
Kerr constant
Opis:
The electro-optical Kerr effect finds wide application in conformational analysis of molecules and molecular aggregates [1–5], particularly in cases where the standard X-ray and NMR techniques cannot be used. For instance, NMR allows to establish conformations of linear and cyclic unsaturated organic compounds. However, it is less effective in an analysis of molecular complexes, particularly of those that have several rotational symmetry axes. In such cases a combination of techniques based on molecular dipole moments, electro-optical Kerr effect, optical Kerr effect, IR spectroscopy, and Rayleigh scattering can be applied [6]. The foundations of conformational analysis of molecular complexes using several complementary physical approaches are developed in Ref. [7]. The electro-optical methods are particularly useful for an investigation of intramolecular interactions [8–18]. The strength, direction and other details of intramolecular interactions can be determined by analyzing the deviations of the experimental molar Kerr constant (mK) from its value calculated according to the tensor-additive scheme that operates with polarizability tensors of molecular cores and functional groups [19, 20]. For instance, using this approach it has been shown that weakening of conjugation in an electron donor-acceptor chain can lead to flattening of the molecular structure [21]. The Kerr constant is also very sensitive to intermolecular interactions [22–29]. In order to assess quantitatively an extent of the solvent effect on the mK values, both molecular and continuum models of solution structure have been used [30, 31]. The mK values are greatly affected by the mutual orientation of solvent and solute molecules, which interact by dispersive, inductive and dipole-dipole forces [32]. Hydrogen and donor-acceptor bonding have an even stronger influence on the mK values [33]. The equimolar mixtures approach developed in Ref. [34] allows to determine the molar Kerr constant (mK), dipole moment (m), equilibrium constant (K) and, ultimately, structure of a molecular complex based on measurements of the Kerr constant (B), dielectric permittivity (e), density (d) and refractive index (n) of a series of dilute solutions of the complex. Future trends in the development of the electro-optical methods in chemistry are discussed. Theories that relate the electric-optic proprieties of molecules with their reactivity are particularly important. Such theories should be able to predict the changes in the polarizabilities and dipole moments of bonds, molecules and molecular aggregates during the course of chemical reactions.
Źródło:
Wiadomości Chemiczne; 2011, 65, 1-2; 1-31
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
O kilku osobliwościach w oddziaływaniach molekuł
On some pecularities of intermolecular and intramolecular interactions
Autorzy:
Piela, L.
Powiązania:
https://bibliotekanauki.pl/articles/172004.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
globalna optymalizacja
zwijanie białek
oddziaływanie dipol-dipol
choroba prionowa
autokataliza
global optimization
protein folding
dipole-dipole interaction
prion disease
autocatalysis
Opis:
The ground state electronic energy represents a complicated function of the nuclear coordinates. Even for relatively small molecules this function may have many minima in the corresponding "energy landscape", very often myriads of minima, each of them corresponding to a stable configuration of the nuclei. This is why predicting the lowest-energy conformation or configuration represents a formidable task. There were many attempts to solve this problem for protein molecules, for which it is believed their native conformation corresponds to the lowest free energy. The challenge to find this conformation from a given sequence of amino acids is known as a "second genetic code". In fact all of these attempts based on some smoothing of the energy landscape. In the article some of these smoothing techniques are described, from a generic one to those, which finally turned out to be highly successful in finding native structures of globular proteins. When discussing the contributions to the conformational energy the importance of the hydrophobic effect as well as of the electrostatic interactions has been stressed. In particular it turned out that the dipole moments of the NH and of the CO bonds in proteins functioning in nature are oriented to good accuracy along the local intramolecular electric field. Thanks to enormous effort of the protein folding community it is possible to design such amino acid sequences, which fold to the desired protein 3D structure. A certain reliable theoretical technique of protein folding has been used to study a possibility of conformational autocatalysis. It turned out that a small protein of 32 amino acids, with carefully predesigned amino acid sequence, exhibits indeed such an effect, which may be seen as a model of the prion disease propagation.
Źródło:
Wiadomości Chemiczne; 2011, 65, 11-12; 935-952
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wiązania chalkogenowe : początki oraz znaczenie w układach biologicznych
Chalcogen bonds : origins and importance in biological systems
Autorzy:
Bucka, Alicja
Dopieralski, Przemysław
Powiązania:
https://bibliotekanauki.pl/articles/172608.pdf
Data publikacji:
2020
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
wiązanie chalkogenowe
niekowalencyjne odziaływania międzycząsteczkowe
niekowalencyjne odziaływania wewnątrzcząsteczkowe
„dziura” sigma
chalcogen bond
intra and intermolecular Noncovalent Interactions
sigma hole
Opis:
The chalcogen bond is analogous to the halogen and hydrogen bond and it produces favorable interactions between 16th group of elements, that play a role in catalysis, medical chemistry, design of materials and biological processes. In the solid state, the chalcogen bond was used to build nano-sized structures and in solution is responsible mainly for intramolecular interactions, which stabilize the structures of intermediates and reagents. Recently, chalcogen bonds have been increasingly used in the recognition and transport of anions and in organic synthesis.
Źródło:
Wiadomości Chemiczne; 2020, 74, 9-10; 663-686
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
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